Black-tailed Prairie Dog (Cynomys ludovicianus): COSEWIC assessment and status report 2024

Official title: COSEWIC Assessment and Status Report on the Black-tailed Prairie Dog (Cynomys ludovicianus) in Canada

Committee on the status of Endangered Wildlife in Canada (COSEWIC)

Threatened

2024

COSEWIC assessment summary

Assessment summary – November 2024

Common name

Black-tailed Prairie Dog

Scientific name

Cynomys ludovicianus

Status

Threatened

Reason for designation

In Canada, this medium-sized rodent is a prairie specialist found only in southern Saskatchewan. Its restricted distribution, vulnerability to increasing drought frequency and Sylvatic Plague - both of which may cause rapid population declines - threatens its persistence in Canada. Anticipated increases in drought frequency, which especially combined with severe winters, can negatively impact populations. Local knowledge suggests the species is resilient to drought based on their long experience in the area. Disease, especially Sylvatic Plague, is a significant potential threat, exacerbated by low genetic diversity and connectivity among colonies that facilitates disease transmission. However, conservation management actions and land stewardship mitigate this extirpation risk.

Occurrence

Saskatchewan

Status history

Designated Special Concern in April 1978. Status re-examined and confirmed in April 1988, April 1999 and November 2000. Status re-examined and designated Threatened in November 2011. Status re-examined and confirmed in November 2024.

COSEWIC executive summary

Black-tailed Prairie Dog

Cynomys ludovicianus

Wildlife species description and significance

The Black-tailed Prairie Dog (Cynomys ludovicianus) is one of five prairie dog species, and the only one that occurs in Canada. They are medium-sized ground squirrels, yellowish to reddish brown in coloration with a black-tipped tail. They live in colonies consisting of extensive burrow systems surrounded by short vegetation.

The feeding and burrowing activities of Black-tailed Prairie Dogs alter the composition of vegetation and create habitat and shelter for other prairie species, including rare and endangered animals such as the Burrowing Owl, Ferruginous Hawk, Mountain Plover, Prairie Rattlesnake, and Black-footed Ferret.

Aboriginal (Indigenous) knowledge

All species are significant and are interconnected and interrelated. There is no species-specific Indigenous knowledge in the report. However, Indigenous names for Black-tailed Prairie Dog exist (ᐸᓱᐊᐧᐦᑫᓰᐢ pasowahkesîs [Cree]; pispíza [Lakota]), which suggests that this may be an important source of knowledge that could be tapped.

Distribution

Historically, Black-tailed Prairie Dogs occurred from southern Saskatchewan in Canada, south to the states of Chihuahua and Sonora in northern Mexico, and from the central lowlands of the Great Plains west to the eastern foothills of the Rocky Mountains. As Europeans settled the Great Plains and converted native prairie to croplands and urban areas, widespread persecution of Black-tailed Prairie Dogs as an agricultural pest and the accidental introduction of sylvatic plague eliminated the species from 98% of its former range. However, the grassland habitat that prairie dogs inhabit in Canada today is still present owing to the long-term land management practices of local ranchers.

In Canada, Black-tailed Prairie Dogs are restricted to approximately 25 colonies in and around Grasslands National Park in southern Saskatchewan. This complex of colonies is separated from the remainder of the species’ range by more than the known dispersal distance. Genetic research confirms their isolation from the rest of the species’ range.

Habitat

Black-tailed Prairie Dogs generally inhabit broad, flat river valleys characterized by short grassy vegetation with few shrubs and well-drained, relatively deep soil with few rocks. Both the mix of plant species and the vertical structure of vegetation are important in determining suitable habitat.

In Canada, Black-tailed Prairie Dogs primarily inhabit the bottom and lower slopes of the Frenchman River Valley. The majority of colonies are located within Grasslands National Park, where the species has reasonable protection from further habitat loss associated with human activities.

Biology

Black-tailed Prairie Dogs are born underground in spring in litters of 1 to 8 individuals and first emerge from their natal burrow approximately six weeks later. They spend summers foraging to acquire sufficient body mass for hibernation. Survival and reproduction are affected by food abundance, which is affected by precipitation and temperatures during the growing season. Winter severity, predation, and disease, particularly sylvatic plague, are also important drivers of population dynamics. Black-tailed Prairie Dogs typically become sexually mature at two years of age and breed once a year. Family groups typically consist of a dominant male and multiple related females plus their young. Males live up to five years of age and females up to eight years.

Population sizes and trends

Adult population size is challenging to ascertain; however, population density and abundance estimates of mature individuals using visual count and mark-recapture data obtained since 2004, show that the species has experienced periods of rapid decline and growth. Since a historical low in 2013, the estimated population of mature individuals has experienced peaks in estimated abundance in 2017 and 2022 and crashes in 2018 and 2023. Long-term projections incorporating the best available data on expected changes in climate and plague suggest that the species’ persistence in Canada may be at risk in the coming decades, although there is much uncertainty in these projections.

Threats

In Canada, Black-tailed Prairie Dogs are most threatened by increased frequency of drought and epizootic outbreaks of sylvatic plague. The frequency and severity of these threats are expected to increase with climate change. Other threats noted include temperature extremes (particularly severe winters following on dry summers). The overall threat impact is Very high/High.

Protection, status, and recovery activities

The Black-tailed Prairie Dog is listed as Threatened on Schedule 1 of the federal Species at Risk Act (SARA), and as Least Concern on the IUCN Red List. NatureServe has ranked the Black-tailed Prairie Dog as G4 (Apparently Secure) globally, N2 (Imperilled) nationally, and S2 (Imperilled) provincially. In 2024 COSEWIC reassessed this species as Threatened.

The majority of habitat for the Black-tailed Prairie Dog in Canada is located within Grasslands National Park and is under federal ownership and protected under the Canada National Parks Act. Additional habitat occurs on Crown land within neighbouring pastures leased from the province.

Recovery actions undertaken since the previous COSEWIC status assessment (COSEWIC 2011) include (1) the publication of the Black-tailed Prairie Dog Recovery Strategy and Action Plan, including the identification of Critical Habitat, and the Multi-species Action Plan for Grasslands National Park which includes actions for the Black-tailed Prairie Dog; (2) research on prairie dogs including demographics, genetics, ecology, and behaviour; (3) monitoring and mitigation of sylvatic plague; (4) management and improvement of habitat; and (5) some discussions with ranchers/landowners to reduce human–prairie dog conflicts and improve relationships with government officials.

Technical summary

Cynomys ludovicianus

Black-tailed Prairie Dog

Chien de prairie à queue noire

ᐸᓱᐊᐧᐦᑫᓰᐢ pasowahkesîs (Cree); pispíza (Lakota)

Range of occurrence in Canada: Saskatchewan

Demographic information:

Generation time (usually average age of parents in the population)

Approximately 3.03 years

Based on Method 3 (IUCN Standards and Petitions Subcommittee 2010) and cumulative life table from Hoogland (1995)

Is there an [observed, estimated, inferred, or projected] continuing decline in number of mature individuals?

No

None observed or estimated but wide fluctuations and uncertainty in estimates of abundance. Potential projected decline based on population viability analysis; however, the models included total population size estimates but not number of mature individuals.

[Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 3 years [or 1 generation; whichever is longer up to a maximum of 100 years]

Unknown

Decline in the past 3 years, which is not considered a continuing decline but rather part of a fluctuation based on longer-term records. Large uncertainty in estimates of abundance.

[Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 5 years [or 2 generations; whichever is longer up to a maximum of 100 years]

Unknown

Decline in the past 2 generations. This is not considered a continuing decline but part of fluctuation based on longer-term records. Large uncertainty in estimates of abundance.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last 10 years [or 3 generations; whichever is longer]

Unknown

Increase in the last 10 years which encompasses several fluctuations. Large uncertainty in estimates of abundance.

[Projected, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations, up to a maximum of 100 years]

Unknown

Population viability analysis model suggests long-term (that is, 20 year) risk of decline with very high uncertainty. Threat impact is Very high/ High.

[Observed, estimated, inferred, projected, or suspected] percent [reduction or increase] in total number of mature individuals over any period of 10 years [or 3 generations; whichever is longer, up to a maximum of 100 years], including both the past and future (up to a maximum of 100 years in future)

Unknown

Decline in the past depending on the time interval chosen, but part of population fluctuations and potential projected decline based on population viability analysis with wide credible intervals.

Are the causes of the decline clearly reversible?

Unknown

Past and future declines are likely attributable to drought which remains a High–Medium impact threat due to likelihood of the frequency and/or duration of drought increasing due to climate change.

Are the causes of the decline clearly understood?

Yes

Past and future declines are likely attributable to frequency of drought but could also be tied to enzootic outbreaks of sylvatic plague.

Are the causes of the decline clearly ceased?

No

Past and future declines are likely attributable to frequency of drought, which is predicted to increase due to climate change. In addition, the spread of sylvatic plague in the ecosystem is expected to increase.

Are there extreme fluctuations in number of mature individuals

Yes

Several large fluctuations have been observed, including one that is considered an extreme fluctuation (1 order of magnitude) over the past two decades.

Extent and occupancy information:

Estimated extent of occurrence (EOO)

472 km²

Calculated based on minimum convex polygon around known occurrences in 2021.

Index of area of occupancy (IAO), reported as 2x2 km grid value

168 km²

Calculated based on known records from 2021.

Is the population “severely fragmented”, that is, is >50% of individuals or >50% of the total area “occupied” (as a proxy for number of individuals) in habitat patches that are both (a) smaller than required to support a viable subpopulation, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

1. No
2. No

Although the population is considered isolated from the rest of the species’ range and its distribution is restricted within Canada, all colonies are presumed to be within dispersal distance of their nearest neighbour and collectively support a viable population.

Number of “locations” (use plausible range to reflect uncertainty if appropriate)

1

All prairie dogs in Canada are found in a single geographic area and could be simultaneously affected by an epizootic plague outbreak or severe drought.

Is there an [observed, inferred, or projected] continuing decline in extent of occurrence?

No

Observed decline based on trends in colony distributions over the past 30 years. EOO has been relatively stable.

Is there an [observed, inferred, or projected] continuing decline in area of occupancy?

No

Observed based on trends in colony distributions over the past 30 years

Is there an [observed, inferred, or projected] continuing decline in number of subpopulations?

No

No subpopulations

Is there an [observed, inferred, or projected] continuing decline in number of “locations”?

No

There is only a single location in Canada based on the most serious plausible threat which is the spread sylvatic plague

Is there an [observed, inferred, or projected] continuing decline in [area, extent and/or quality] of habitat?

Yes

Projected continuing decline in quality of habitat due to increasing frequency of drought

Are there extreme fluctuations in number of subpopulations?

No

There is only a single population in Canada

Are there extreme fluctuations in number of “locations”?

No

There is only a single location in Canada

Are there extreme fluctuations in extent of occurrence?

No

Are there extreme fluctuations in index of area of occupancy?

No

Number of mature individuals (by subpopulation):

Subpopulation 1

Unknown/Not Applicable

There are no subpopulations.

Total

Between 8,291 and 9,396 mature individuals

Direct estimates of mature individuals do not exist. The estimate provided here must be interpreted with caution (see Abundance).

Quantitative analysis

Is the probability of extinction in the wild at least 20% within 20 years [or 5 generations], or 10% within 100 years]

Yes

Population viability analysis model reports a 50% mean relative probability of extinction within 20 years, although the large 95% credible interval suggests considerable uncertainty in this estimate

Threats

Was a threats calculator completed for this species?

Yes; October 24, 2022; Appendix 1

Overall assigned threat

impact: Very high/High

Key threats were identified as:

Invasive non-native/alien species/diseases (IUCN 8.1) - Very high/High impact

Droughts (IUCN 11.2) - High/Medium impact

What limiting factors are relevant?

• reproductive phenology

Rescue effect (from outside Canada):

Status of outside population(s) most likely to provide immigrants to Canada.

S3 Vulnerable in Montana

Is immigration known or possible?

Unlikely

The closest known colony/complex in the U.S. is beyond the documented dispersal distance for the species; however, the species’ dispersal capabilities are not well understood. Unlikely based on genetic data.

Would immigrants be adapted to survive in Canada?

Yes

Is there sufficient habitat for immigrants in Canada?

Unknown

Likely based on estimates of potential habitat.

Are conditions deteriorating in Canada?

No

Observed based on colony extent and population density data

Are conditions for the source (that is, outside) population deteriorating?

Not Applicable

Is the Canadian population considered to be a sink?

No

Is rescue from outside Canada likely, such that it could lead to a change in status?

Unlikely

Wildlife species with sensitive occurrence data (general caution for consideration):

Could release of certain occurrence data result in increased harm to the Wildlife Species or its habitat?

Yes, for some occurrences

There are no concerns for the data presented in this report. However, disclosing the location of colonies outside of the park may result in increased persecution.

Status history:

COSEWIC

Designated Special Concern in April 1978. Status re-examined and confirmed in April 1988, April 1999 and November 2000. Status re-examined and designated Threatened in November 2011. Status re-examined and confirmed in November 2024.

Status and reasons for designation:

Status

Threatened

Alpha-numeric codes

D2

Reason for change in status

Not applicable; no change in status

Reasons for designation

In Canada, this medium-sized rodent is a prairie specialist found only in southern Saskatchewan. Its restricted distribution, vulnerability to increasing drought frequency and Sylvatic Plague - both of which may cause rapid population declines - threatens its persistence in Canada. Anticipated increases in drought frequency, which especially combined with severe winters, can negatively impact populations. Local knowledge suggests the species is resilient to drought based on their long experience in the area. Disease, especially Sylvatic Plague, is a significant potential threat, exacerbated by low genetic diversity and connectivity among colonies that facilitates disease transmission. However, conservation management actions and land stewardship mitigate this extirpation risk.

Applicability of criteria:

A: Decline in total number of mature individuals:

Not applicable.

The most current population estimate indicates that the population has fluctuated but not declined in total number of mature individuals over the long term. There have been several population fluctuations. However, there is large uncertainty in estimates of density and population size.

B: Small range and decline or fluctuation

Not applicable.

Both EOO (472 km²) and IAO (168 km²) meet the thresholds for Endangered, and the population is known to exist at fewer than 5 locations. Although this species has experienced population fluctuations, they have been less than an order of magnitude in number of mature individuals, and there is no evidence of continuing decline in any of the subcriteria.

C: Small and declining number of mature individuals

Not applicable.

Population estimates indicate that the number of mature individuals (8,291 to 9,396) is below the 10,000 threshold for Threatened. However, there is no continuing decline in number of mature individuals over 3 generations.

D: Very small or restricted population

Meets Threatened, D2.

Restricted to 1 location and prone to substantial decline from effects of stochastic events within 1-2 generations (mainly increased drought frequency, especially in combination with severe winters, and susceptibility to diseases (for example, sylvatic plague)).

E: Quantitative analysis

Not applicable.

Population projections estimated from the population viability analysis suggest a 50% probability of extirpation in Canada which exceeds the threshold of 20% probability within 20 years for Endangered status. However, the extremely wide credible intervals (0.1 to 1) suggest considerable uncertainty in this projection.

Preface

Since the publication of the 2011 COSEWIC status report, Grasslands National Park has developed an Ecological Integrity Monitoring Framework and continued to conduct annual population surveys along with colony extent mapping approximately every other year within and around Grasslands National Park. In collaboration with Grasslands National Park, the Wilder Institute/Calgary Zoo and the University of Saskatchewan have conducted new research studies on population genetics, sylvatic plague, dispersal, hibernation, reproductive phenology, seasonal mass dynamics, and social structure. A Multi-species Action Plan for Grasslands National Park was completed in 2016, and the Recovery Strategy and Action Plan for the Black-tailed Prairie Dog was finalized in 2021. An updated population viability analysis was developed in 2021. The reintroduction of Black-footed Ferrets (Mustela nigripes; a specialist predator of Black-tailed Prairie Dogs) to Grasslands National Park ceased in 2013, the same year the last wild ferret was observed in Canada.

The Rural Municipality (RM) of Val Marie and local ranchers have expressed considerable concern about the original listing and subsequent status assessments . To understand these concerns, several members of COSEWIC travelled to Grasslands National Park and Val Marie to meet with community members. Valuable community knowledge was shared with the Terrestrial Mammal SSC, and this was incorporated into the report.

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2024)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)^*

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)^**

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)^***

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

^* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
^** Formerly described as “Not In Any Category”, or “No Designation Required.”
^*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.

Wildlife species description and significance

Name and classification

Current classification: Cynomys ludovicianus (Ord 1815)

Class: Mammalia

Order: Rodentia

Family: Sciuridae

Genus: Cynomys

Species: Cynomys ludovicianus (Ord 1815)

Taxonomic changes since previous report (for reassessments): None

Common names:

English: Black-tailed Prairie Dog

French: Chien de prairie à queue noire

Indigenous: ᐸᓱᐊᐧᐦᑫᓰᐢ pasowahkesîs (Cree), pispíza (Lakota)

Synonyms and notes:

Of the five species of prairie dog endemic to North America, only the Black-tailed Prairie Dog lives in Canada. There are two recognized subspecies of Black-tailed Prairie Dog (Wilson and Reeder 2005): the widespread C. l. ludovicianus (Banfield 1974; Hoogland 1995), to which the Canadian population belongs, and C. l. arizonensis, found only in northern Mexico and southwestern United States (U.S.).

Description of wildlife species

Black-tailed Prairie Dogs (also referred to herein as “prairie dogs”) are medium-sized, herbivorous, and semi-fossorial ground squirrels (Sciuridae). The overall coloration of their fur is yellowish-brown to reddish-brown, except on the belly and chest where it is off-white. Their tail is approximately 1/3 of their total body length with a distinct black tip, hence the common name “Black-tailed Prairie Dog.” Prairie dogs moult twice a year, in the spring and fall, but the colour of their fur remains the same. They are adapted for digging extensive burrow systems, given their short legs, long phalanges and claws. Black-tailed Prairie Dogs are the largest of the five prairie dog species. In Canada, adult prairie dogs measure between 26 and 35 cm in length from nose to base of tail (Wilder Institute/Calgary Zoo unpub. data). Mean weights fluctuate over the year, but range from 964 g ± 52 g to 1,354 g ± 57 g in males and from 842 g ± 29 g to 1,141 g ± 51 g in females over the summer growing season (Wilder Institute/Calgary Zoo unpub. data).

The Black-tailed Prairie Dog and Richardson’s Ground Squirrel (Urocitellus richardsonii) are closely related (Herron et al. 2004) and commonly confused for one another. In Canada, Richardson’s Ground Squirrels are frequently found living in prairie dog colonies (Liccioli et al. 2020; Parks Canada Agency 2021), but can be distinguished from Black-tailed Prairie Dogs by their size, coloration, and behaviour. Richardson’s Ground Squirrels are smaller and more-slender (18 to 23 cm), with yellow-brown to grayish fur, and a shorter tail (~1/4 of their body length) that is blackish-brown with whitish hairs on the outer edges and tip.

Designatable units

There is only one subspecies of Black-tailed Prairie Dog that occurs in Canada, and all colonies in Canada are assumed to be linked through dispersal which would preclude the formation of “discrete” and “evolutionarily significant” designatable units.

Special significance

Black-tailed Prairie Dogs are considered ecosystem engineers due to their foraging and burrowing activities. These activities, concentrated within their colonies, transform the landscape into a mosaic of habitat patches characterized in some regions by an increase in forage quality, altered vegetative species composition (Coppock et al. 1983b; Whicker and Detling 1988), and extensive burrow systems that provide refuge for other prairie-adapted species (Kotliar 2000). Some researchers therefore consider prairie dogs to be a keystone species (Kotliar et al. 1999, 2006; Lomolino and Smith 2003; Miller et al. 2000, 2007; Davidson et al. 2012) whose ecological importance is disproportionate to their biomass (Ceballos et al. 1993, 2005; Stapp 1998; Davidson and Lightfoot 2006; Kotliar 2000). Many of the species that benefit from prairie dogs are themselves rare or endangered, such as the Burrowing Owl (Athene cunicularia), Ferruginous Hawk (Buteo regalis), Mountain Plover (Charadrius montanus), and Prairie Rattlesnake (Crotalus viridis).

The prairie dog’s densely occupied colonies provide a concentrated prey source for a variety of predators (Kotliar 2000; Davidson et al. 2012). Of particular importance is the close predator-prey relationship between the Black-footed Ferret (also referred to herein as “ferrets” unless the species is unclear) and the Black-tailed Prairie Dog. The heavy prey reliance of ferrets on the diminishing prairie dog population (Brickner et al. 2014) led to the ferret’s near-extinction in the early 20th century. Years of agricultural land conversion and lethal control of prairie dogs, along with the accidental introduction of the sylvatic plague (Yersinia pestis) to North America, led to a massive reduction in the ferret population across its entire range, including its extirpation from Canada in 1937 (Lockhart et al. 2006). Although efforts to reintroduce the ferret to Grasslands National Park led to a brief return of the species to Canada between 2009 and 2013, declining prairie dog populations triggered a suspension of the program, and the Black-footed Ferret remains assessed as Extirpated (Parks Canada Agency 2018; COSEWIC 2021).

Black-tailed Prairie Dogs are also a significant concern to local landowners, particularly when populations are increasing (RM Val Maire pers. comm. 2024). It is recognized that prairie dogs can significantly reduce the availability of forage on their colonies, which can lead to economic costs for cattle ranchers. There is also concern that livestock and horses can be injured in the holes and push-ups created by burrowing prairie dogs. Throughout the species range, efforts are often made to control this species on private lands (Lamb et al. 2006). In Canada, over the years since the establishment of Grasslands National Park, there has been increasing tension around the topic of Black-tailed Prairie Dogs and their status and management (Lamb et al. 2006; Liebenberg 2021). These ongoing concerns highlight the significance of the species and the need for conservation planning that engages all stakeholders.

Given that the Canadian Black-tailed Prairie Dog population encompasses the northern limit of the species’ range, it may play a critical role in the future conservation of the species if the species’ range shifts northward with increasing global temperatures (Stephens et al. 2018).

Aboriginal (Indigenous) traditional knowledge

Indigenous knowledge is relationship-based. It involves information on ecological relationships between humans and their environment, including characteristics of species, habitats, and locations. Laws and protocols for human relationships with the environment are passed on through teachings and stories, and Indigenous languages, and can be based on long-term observations. Place names provide information about harvesting areas, ecological processes, spiritual significance, or the products of harvest. Indigenous knowledge can identify life-history characteristics of a species or distinct differences between similar species.

There is no species-specific Indigenous knowledge in the report. However, Indigenous names for Black-tailed Prairie Dog exist (ᐸᓱᐊᐧᐦᑫᓰᐢ pasowahkesîs [Cree]; pispíza [Lakota]) and thus suggest an important source of knowledge that is present but not available here. Overall, the Black-tailed Prairie Dog is important to Indigenous Peoples who recognize the interrelationships of all species within the ecosystem.

Distribution

Global range

Historically, the range of the Black-tailed Prairie Dog extended from the mixed-grass prairie of southern Saskatchewan in Canada south to Chihuahua and Sonora in northern Mexico, and from the eastern foothills of the Rocky Mountains east to the boundary of the mixed and tall-grass prairies of the central lowlands of the Great Plains (Figure 1; Koford 1958; Hall 1981; Hoogland 1995; Parks Canada Agency 2021). In the late 19th century, the expansive range was estimated to span more than 160 million hectares (ha), of which an estimated 30 million ha were effectively occupied by Black-tailed Prairie Dog colonies (Knowles et al. 2002, but see Vermeire et al. 2004). However, by the end of the 20th century, all but an estimated 2% of the historical distribution had been extirpated due to habitat loss, widespread eradication programs (Miller et al. 1996; Anderson et al. 1986; Detling 2006), and disease outbreaks that came with European settlement (Miller et al. 1990; Knowles et al. 2002; Miller et al. 2007; but see Vermeire et al. 2004). Today, the remaining Black-tailed Prairie Dog colonies largely persist in small, isolated complexes in protected areas which span the historical distribution (Hoogland 2006; Miller et al. 2007; Davidson et al. 2022).

Figure 1. The historical geographic range of the Black-tailed Prairie Dog (Cynomys ludovicianus). (Source: Darekk2 Wikimedia Commons). The map was created from IUCN Red List spatial data using Generic Mapping Tools, GMT, version 5.1.1).

Canadian range

The Canadian distribution of the Black-tailed Prairie Dog occupies less than 1% of the species’ global range. Both the historical and current documented range of the species is restricted to a small geographic region in the mixed-grass prairie within the Treaty 4 traditional and unceded territories of the Ĩyãħé Nakón mąkóce (Stoney), Niitsítpiis-stahkoii ᖹᐟᒧᐧᐨᑯᐧ ᓴᐦᖾᐟ (Blackfoot / Niitsítapi ᖹᐟᒧᐧᒣᑯ), Očhéthi Šakówiŋ, Cayuse, Umatilla, and Walla Walla Nations, and the Michif Piyii (Métis) peoples, of southern Saskatchewan (Native Land Digital 2024). A summary of what is known about the historical Canadian range, dating back to 1927, is provided in Appendix 2. Observational records suggest that Black-tailed Prairie Dogs have generally been confined to Saskatchewan’s Frenchman River Valley (where they are still found today); however, reports of Black-footed Ferret specimens collected from areas beyond this region (Anderson et al. 1986) may suggest a wider historical distribution of prairie dogs (ostensibly, their obligate prey) (Appendix 2).

The current Canadian population of prairie dogs is restricted to approximately 25 colonies in Grasslands National Park and neighbouring pastures. The nearest individual colony that belongs to a separate population of Black-tailed Prairie Dogs is located approximately 20 km away, in Montana. The nearest colony complex is approximately 60 km away, also in Montana. Dispersal distances are not well known for the species, with direct observation of movement less than 10 km (Garrett and Franklin 1988; Milne 2004) and genetic analysis suggesting dispersal of 40 to 60 km (Pigg 2014). Although it is possible that Grasslands National Park and some U.S. populations are within dispersal distance, genetic analysis suggests that there has been no recent or ongoing dispersal between Canada and the U.S. populations (Cullingham et al. 2023).

Since the establishment of Grasslands National Park in 1981, search efforts for Black-tailed Prairie Dogs have been consistent but generally biased towards areas of active or recent occupancy. There are no standardized efforts to identify new or re-established historical colonies within or outside of the park. The documentation of five new colonies in the Park in 2020/2021 were made opportunistically by Parks Canada staff who were working in the park and heard prairie dog yips nearby.

In total, 25 Black-tailed Prairie Dog colonies are currently occupied in Canada, 23 of which are located within the Grasslands National Park and two on adjacent community pastures. Two additional colonies are known to have been occupied in recent years, but are vacant at present.

Population structure

Canadian Black-tailed Prairie Dogs are distributed among an assemblage of spatially distinct colonies (or “towns”) that are within the documented dispersal capabilities of the species (<10 km; Garrett and Franklin 1988; ~20 km Masefield Pasture Association Board pers. comm. 2023) and presumably function as a single population (Knowles et al. 2002; Roach et al. 2001). They are therefore considered a single designatable unit (See Designatable units).

An introduced population of Black-tailed Prairie Dogs east of Edmonton, Alberta, over 600 km northwest of the natural prairie range of the species (Trefry and Holroyd 2012), is now extirpated. A small, escaped population also exists at Fort Whyte Alive in Winnipeg, Manitoba, well outside the species’ natural range. This population is not included in the assessment following the COSEWIC guidelines for manipulated populations (COSEWIC O&P Manual).

In 2023, there were 25 active prairie dog colonies documented, all located within a 472 km² area in southern Saskatchewan, 23 of which are within Grasslands National Park. These colonies range in size from 0.4 ha to 190 ha. An unknown number of colonies persist outside the boundary of Grasslands National Park on private lands, but their size and locations have not been disclosed by landowners, due to political sensitivities. It is presumed that these are within the estimated dispersal distance for Black-tailed Prairie Dogs; therefore, they are still considered part of a single location. Although dispersal between colonies has not been directly documented in Canada (see Movement, migration, and dispersal), the perceived extirpation and recolonization of a small colony between 2013 and 2016 suggests that dispersal does occur and may be critical to the persistence of the species (Gilpin 1996; Hanski and Gilpin 1997) in Canada.

A recent genetic study genotyped over 500 individuals at 15 microsatellite loci using hair samples from 15 of the 23 colonies located within Grasslands National Park, in addition to 1,000 base pairs of mtDNA, which were sequenced from a subset of the individuals within each sampled colony (Cullingham et al. 2023). The resulting analysis indicates there is extremely low genetic variability (Ho=0.231) within the Canadian population and little genetic structure among colonies.

Within each colony, prairie dogs live in territorial family groups, known as coteries (Hoogland 1995). Coteries typically consist of one breeding male, several breeding females, and related yearlings and juveniles (Hoogland 1995, 2006). However, a recent study of a single colony in Canada found that some coteries were comprised entirely of yearlings, as well as a mix of adult females and yearlings, without a breeding male (Kusch and Lane 2021). In the U.S., coteries are reported to consist, on average, of 6.5 family members (range 1 to 26), with mean coterie territories occupying between 0.31 ha (range: 0.05 ha–1.01 ha; Hoogland 1995) and 0.85 ha (range: 0.5 ha–1.8 ha; Geaumont et al. 2018). Although the mean number of individuals in a family group reported for Canada is consistent with U.S. reports (mean: 6.61, range 1 to 14), the territory size of Canadian prairie dogs is considerably smaller with an average of only 0.04 ha (range: 0.02 ha–0.07 ha; Kusch and Lane 2021).

Further information on connectivity and barriers to movement among colonies is needed to better understand how spatial structuring of colonies may influence the genetic structure, demographic isolation, and ultimately the persistence of Black-tailed Prairie Dog in Canada.

Extent of occurrence and area of occupancy

A total of 28 Black-tailed Prairie Dog colonies were mapped in Canada over the course of 18 surveys conducted between 1970 and 2023 (Table 1). Prior to 1992, the methodology for mapping colony extent was not standardized (COSEWIC 2011; Appendix 3). Therefore, only data from 1992 to 2023 were used to generate estimates of Extent of occurrence and area of occupancy in this report.

Although technology and methodology have evolved slightly over the years since 1993, colony extent surveys conducted by Parks Canada and partners have generally used the “active burrow” monitoring technique (for example, active burrows are open and have fresh scat; Biggins et al. 1993) recommended by Gauthier and Boon (1994). In this protocol, the outer perimeters of all known colonies in Grasslands National Park and the neighbouring community pastures (pending annual permission) but not those on private deeded land, are mapped using a handheld GPS unit while walking from active burrow to nearest active burrow at the edge of the colony to determine the colony extent. This technique is both straightforward and repeatable (Grasslands National Park 2022); however, distinguishing between active and inactive burrows can be difficult and subjective at times. Therefore, annual maps of prairie dog colony extent should be considered to represent approximate boundaries only, given that the extent of influence that prairie dogs have on the grassland may extend farther than the peripheral burrows.

Current EOO:

Extent of occurrence (EOO) within Canada is 472 km², calculated using a minimum convex polygon that encompasses known colony extent records from 2023 for most colonies and from 2019 for the Masefield colony (Figure 2).

Figure 2. Estimated area of colony activity (2023), Index of Area of Occupancy (IAO), and 2023 Extent of Occurrence (EOO; “2023 Minimum Convex Polygon”) for Black-tailed Prairie Dogs in Canada. All colonies were mapped in 2023 with the exception of the Masefield colony, which was last surveyed in 2019 and is located to the far southwest of the others, outside the Grasslands National Park boundary. Using the 2019 extent for Masefield, and the 2023 extents for all other colonies, EOO (minimum convex polygon) is estimated to be 472 km². The IAO estimated at the scale of 2 km x 2 km cells is 168 km². All data were provided by Grasslands National Park.

Current IAO:

The index of area of occupancy (IAO) within Canada is 168 km², calculated using a 2 x 2 km grid drawn over known colony extent records from 2023 for most colonies and from 2019 for the Masefield colony (Figure 2).

Local community members indicate that there are unsurveyed prairie dog colonies outside the park, but their locations are kept confidential by the landowners. Assuming that the EOO and IAO are underestimated, and to understand the sensitivity of these metrics to influence the fit with the criteria threshold, the maximum likely EOO and IAO was calculated with a 20% spatial buffer (Table 2). The total EOO (the largest possible measure of occupied area) is 566.7 km² including a 20% buffer. The 2 km x 2 km IAO is 202 km² including a 20% buffer. Despite the 20% buffer, both the EOO and IAO estimates remain well below the COSEWIC thresholds of 5,000 km² and 500 km², respectively.

Fluctuations and trends in distribution

Over the past 30 years (1992 to 2023), the EOO for Canadian Black-tailed Prairie Dogs has remained relatively consistent, except in 2011 to 2015, when the most southern colony (that is, the South Gillespie colony) was temporarily extirpated. The EOO has remained between 450 and 475 km², with relatively minor variations among years (Table 3). Similarly, the 2 km x 2 km IAO rarely fluctuated more than 10% between consecutive surveys (Table 3), with the largest longer-term increase (20%) occurring from 2013 to 2021 (Table 2).

*Masefield colony removed for comparison with 2021 dataset (a year when Masefield was not mapped).

**2019 Masefield colony estimate included here for comparison with 2019 full dataset.

The largest increase in total colony extent between two consecutive surveys over the last two decades occurred from 2019 to 2021 (39.7%) (Figure 3). On average, each colony’s extent (not population) increased by 64% between these two surveys—the highest mean increase in extent recorded to date (Table 4). The documentation of five newly establishing colonies in 2020 and 2021 (Walker South, Big Blue Stem, Little Blue Stem, and two colonies close to the Grasslands National Park bison facility in the vicinity of two historical colonies documented in 1970) was also a sign of a general increase in prairie dog distribution in recent years. In 2020, prairie dogs also began to colonize the Frenchman River Valley campground, but were translocated to the periphery of the Sage colony in the same year. The apparent expansion of prairie dogs into new (or former) habitat aligns with observations made by community members who reported seeing prairie dogs in areas outside of Grasslands National Park, from which they have been absent for years (Grant pers. comm. 2022; Masefield Pasture Association Board pers. comm. 2023).

A standardized method for recording prairie dog colony extents has supported temporal comparisons of active colony sizes for over two decades. However, surveys for new prairie dog colonies, particularly outside of Grasslands National Park, are not regularly conducted.

Figure 3. Estimated colony extents for Black-tailed Prairie Dogs in Canada. The total colony area (km²) mapped in each survey is represented in dark blue. In years when not all colonies were mapped despite their presence (1992/1993/1994, 1997/1998, 2002, 2004, 2021 and 2023), the area of unmapped colonies was calculated by taking the average of the two adjacent survey years (“adjusted estimate”; light blue). See Table 1 for details. Total colony area in 1970, 1975, and 1985 (gray) is represented separately, because sampling frequency and protocols for those years were inconsistent with those after 1992.

Biology and habitat use

The life history of Black-tailed Prairie Dogs is closely tied to environmental conditions and seasonality, particularly in Canada where severe winters necessitate a four-month hibernation period (see Physiological, behavioural, and other adaptations). The spring months (~March to June) are typically characterized by reproduction prior to green-up, followed by the emergence of pups and a period of dispersal where yearlings and/or adults may leave their natal coterie to join new coteries or colonies (see Movements, migration, and dispersal). The summer months (~July to September) are critical for foraging activities and gaining body mass. Pups grow rapidly during this time, while yearlings and adults regain body mass lost during hibernation and spend time maintaining/creating burrows and defending or expanding territories. In the fall (~September to November), all prairie dogs prepare for hibernation by increasing their fat stores, lining their burrows with dead vegetation and other insulative materials, and undergoing a fall moult.

Life cycle and reproduction

The estimated generation time for prairie dogs is 3.03 years, according to Method 3 (IUCN Standards and Petitions Subcommittee 2010), and the cumulative life table from Hoogland (1995) (COSEWIC 2011). Reproduction in prairie dogs typically begins at two years of age but can occur in yearlings (35%–40% of females, 6% of males) or be delayed until the age of three (5% of females, 24% of males; Knowles 1987; Hoogland 1995). The breeding season typically spans 1 to 4 weeks (King 1955 cited in Knowles 1987; Tileston and Lechleitner 1966; Hoogland 1995), starting in mid- to late March in northern parts of the species’ range (Knowles 1987; Garrett and Franklin 1988). Females come into estrus for a single day, usually once per year, but they can occasionally come into estrus a second time, around 2 weeks later, if they do not become pregnant the first time (Hoogland 1995). The species is polygynous, which means that 1 to 2 males will breed within a coterie with 2 to 3 females who are closely related to each other (Hoogland 1995). Copulation happens below ground in burrows, but mating and courtship behaviours are evident above ground (Hoogland 1995).

In Canada, parturition typically occurs in early April, and juveniles emerge between mid-May and early June (Kusch et al. 2020; Liccioli pers. comm. 2022). The average litter size for Canadian prairie dogs is 3.06 ± 1.27 SE (standard error) pups (Kusch et al. 2020). Litter sizes of up to 8 to 10 have been recorded but likely represent pre-emergence numbers (Anthony and Foreman 1951; Koford 1958; Hoogland 1995). A maximum litter size of eight individuals was recorded in 2019 (J. Lane unpub. data) following a year of low population density.

Annual reproductive rates are influenced by factors such as per capita resource availability (Stephens 2012) and drought (Knowles 1987; Avila-Flores et al. 2010; Facka et al. 2010; Grassel et al. 2016; Stephens et al. 2018). Because reproduction takes place in early spring after adults have just emerged from hibernation and before vegetation green-up, prairie dogs in Canada and other northern parts of the species’ range must rely on energy reserves acquired during the previous growing season. Low pregnancy rates, smaller litter sizes, delayed births, and/or low pup survival can all result from non-optimal body conditions in reproductive adults (Rieger 1996; Neuhaus 2000). Furthermore, energy trade-offs between reproduction and survival can shift under stressful conditions for reproductive individuals (Smith and Johnson 1985). Studies on Canadian prairie dogs report a positive relationship between body mass in the preceding fall and female reproductive status the following spring (Lloyd 2011; Stephens 2012). Canadian prairie dogs studied between 2007 and 2019 showed extreme variations in reproductive rates with widespread failure in years following a drought (Stephens et al. 2018; Kusch et al. 2021; Wilder Institute/Calgary Zoo unpub. data). For example, in 2018 only 0.5% of females were reproductively active. This is the lowest proportion of reproductive females ever documented in Canada and it followed the worst drought conditions (2017) on record for the previous six decades. In years following extreme drought, population-wide reproductive failure has been known to occur (Avila-Flores 2009; Facka et al. 2010).

Black-tailed Prairie Dogs exhibit differences in survivorship between sexes, with males typically living three to five years and females five to eight years (Hoogland 1995). In both sexes, survival rates vary curvilinearly with age (Hoogland 1995) and are highly variable (Grassel et al. 2016; Stephens et al. 2018). Juveniles generally have the lowest survival rates in a population (Hoogland 1995), a situation that has primarily been attributed to infanticide by adult conspecifics and predation (Hoogland 1995, 2001). Yearling and adult male prairie dogs tend to have lower survival rates than females of the same age class, possibly due to male territorial disputes (Hoogland 1995) and male-biased dispersal, which may increase attacks from conspecifics between coteries and increase the risk of predation when moving between colonies (Garrett and Franklin 1988). Although prairie dog colonies provide a concentrated prey source for many predatory species (Hoogland 1981; Loughry 1987), the impact of predation on prairie dog survival rates is not well understood (Koford 1958; Tyler 1968; Campbell III and Clark 1981).

Annual and seasonal variability in forage production, precipitation, and ambient temperature are prominent drivers of Black-tailed Prairie Dog survival across their range (Hoogland 1995: Facka et al. 2010; Stephens et al. 2018). The most limiting time of year for Canadian prairie dogs is between November and April when forage plants have died and temperatures are lowest. Studies conducted during two time periods (2008 to 2010 and 2017 to 2019) reported that survival estimates for winter vary more widely than those for the summer growing season (Lloyd 2011; Wilder Institute/Calgary Zoo unpub. data). Lloyd (2011), which suggests that the variability in winter survival is driven by a combination of precipitation in the previous growing season and winter severity. Stephens et al. (2018) proposed that the quantity and quality of forage driven by variation in precipitation may influence Canadian prairie dog annual survival through four potential mechanisms: (1) reduced forage could reduce body mass, decreasing their ability to survive the winter; (2) reduced forage could lead to higher predation rates due to prairie dogs having to forage further from burrows; (3) reduced forage quality may have physiological effects on thermoregulation, potentially affecting energy regulation over winter; and (4) reduced forage quality could lead to poorer body condition, increasing susceptibility to ectoparasites and disease.

At a landscape level, a significant mortality threat is sylvatic plague transmitted primarily by fleas (Cully and Williams 2001; Antolin et al. 2002; Eisen et al. 2006) (see Threats). In the United States, plague has been documented at enzootic levels that appear to ‘simmer’ on the landscape (low disease prevalence, low mortality, and slow spread) and then erupt into epizootic outbreaks (high disease prevalence, rapid mortality, and spread) characterized by 90% to 100% mortality rates and colony extinctions (Cully and Williams 2001; Antolin et al. 2002; Stapp et al. 2004; Lorange et al. 2005). Liccioli et al. (2020) suggest that in Canada, plague is likely maintained at enzootic levels. However, the contribution of enzootic plague to current survival rates of Canadian prairie dogs is not well understood, and Parks Canada currently carries out a program of active management to reduce the risk (Tuckwell and Everest 2009).

Habitat requirements

Across their range, Black-tailed Prairie Dogs generally inhabit broad, flat river valleys characterized by grasses, forbs, and other relatively short vegetation (<30–cm), and low shrub density (Koford 1958; Clippinger 1989; Hoogland 1995; Proctor 1998; Roe and Roe 2003; Avila-Flores et al. 2010; Stephens 2012; Thorpe and Stephens 2017). They also require well-drained, relatively deep soil (>1–m) with few rocks to establish stable burrow systems (Reading and Matchett 1997; Avila-Flores et al. 2010; Stephens 2012; Calgary Zoo Foundation and Grasslands National Park 2021) that are used for sleeping, hibernating, mating, and pup rearing, as well as for shelter from severe weather conditions and predators (Hoogland 1995).

Most prairie dog colonies in the park are located within the bottom and lower slopes of the Frenchman River Valley. Local ranchers indicate that colonies are on, or near, previously disturbed or cultivated lands and consider this to be an important factor in their habitat selection (RM Val Marie pers. comm. 2024). Specific habitat requirements of Black-tailed Prairie Dog in Canada are primarily derived from comparisons of occupied and unoccupied habitats within Grasslands National Park. Topological and climatic conditions such as low to moderate slope, median values of mean winter radiation, alluvial and colluvial sediments, clay-like soils, and terrain with moderate ruggedness are important for occupancy (Stephens 2012). Thorpe and Stephens (2017) found that the probability of prairie dogs occupying a 60 x 60 m habitat unit (within the 2009 colony extent) was inversely related to each of the following: slope, percent sand, mean winter solar radiation, and organic carbon in the soil. These authors used these variables to predict habitat suitability across Grasslands National Park; their model suggested that approximately 5,600 ha within the park were highly suitable for prairie dogs (including the ~1,200 ha already occupied). This is likely an overestimate, however, because the absence of vegetative variables in the model led to some areas being identified as highly suitable despite poor vegetation and significant wind and water erosion.

Biological variables, such as vegetation characteristics, have been excluded from habitat models to date because prairie dogs heavily modify their environment by clipping vegetation and maintaining burrows (Cincotta et al. 1989). Consequently, the characteristics of occupied colonies do not necessarily reflect those of habitats that could be suitable but are unoccupied. To take vegetation into account, a habitat assessment index was developed in 2021 building on the model by Thorpe and Stephens (2017), in order to evaluate potential prairie dog habitats against a standardized, quantifiable set of criteria (Parks Canada and Wilder Institute/Calgary Zoo 2021). These include abiotic criteria similar to those in existing Canadian models, and biological criteria that are largely informed by research on prairie dog habitat requirements in the U.S. (see Parks Canada and Wilder Institute/Calgary Zoo 2021).

The biological habitat requirements of Black-tailed Prairie Dogs can be grouped into two categories: (1) vegetation composition and (2) vegetation structure and cover. Vegetation composition refers to the quality, quantity, and/or diversity of plants present, while vegetation structure and cover refer to the physical characteristics of those plants, such as their height and density.

Black-tailed Prairie Dogs are herbivores whose diet consists primarily of grasses, shrubs, roots, and seeds. However, they do not rely on any one specific type of plant as the predominant source of food. Prairie dogs thus are opportunists in the sense that their diet, while primarily consisting of grasses and forbs, varies with plant abundance, colony locality, and season. Further, different colonies can have different preferences (Beckstead 1977), meaning that the ideal composition of vegetation in prairie dog habitat(s) likely depends on the nutritional and energetic requirements of a given coterie or colony. For instance, Black-tailed Prairie Dogs in South Dakota consumed young, succulent Fennel-leaved Desert-parsley (Lomatium foeniculaceum) in May, but avoided the plant later in the season as it matured (Fagerstone et al. 1981). Similarly, Western Wheatgrass (Pascopyrum smithii) is frequently consumed by prairie dogs in Montana (Kelso 1939) and South Dakota (Summers and Linder 1978), but is generally avoided in Colorado (Lehmer and Van Horne 2001). Whether the specific diet preferences of Canadian prairie dogs differ greatly from or align with those of conspecifics to the south is unknown. However, for prairie dogs in northern mixed-grass prairie, general preferences for grasses over forbs and young plants over mature have been observed (Summers and Linder 1978; Fagerstone and Williams 1982; Uresk 1984). Habitats with both cool-season (C3) and warm-season (C4) grasses may therefore be more likely to provide adequate food and moisture throughout the active season (Fagerstone and Williams 1982), while readily available and relatively hardy forbs may provide supplemental nutrition during periods when grasses are less palatable (Fagerstone et al.1981).

Vegetation structure is important for predator detection. Prairie dogs generally prefer areas with vegetation shorter than 30 cm because visual predator detection is maximized in areas with short vegetation and unobstructed views (Roe and Roe 2003; Singh 2020). They tend to colonize areas where the vegetation is already short (Koford 1958; Snell 1985; Knowles 1986; Hoogland 1995) and further modify the habitat through rigorous grazing and clipping of tall plants. Avila-Flores et al. (2010) identified herbage height and shrub density as the two most significant variables predicting Black-tailed Prairie Dog occupancy in colonies in northwestern Chihuahua, Mexico, and attributed this to the importance of visibility. Fargey and Marshall (1997) sampled vegetation structure at eight active prairie dog colonies in Grasslands National Park in 1996; their results indicated that most of the vertical structure (an integrated measure of vegetation height and density as assessed by estimating the amount of a checkered board that was visible at different height strata) was at or below 10 cm in height.

Movements, migration, and dispersal

Black-tailed Prairie Dogs are not migratory, but yearlings and adults will disperse between coteries or colonies, often following pup emergence from natal burrows in the spring (Garrett and Franklin 1988; Hoogland 1995; Kusch et al. 2020) (see Life cycle and reproduction). Many of the dispersers are yearlings moving away from their natal territories prior to becoming reproductively active (a well-documented pattern among ground-dwelling sciurids; Garrett and Franklin 1988; Devillard et al. 2004; Nunes 2007). Increased colony density and therefore competition for resources during emergence may motivate mature individuals to leave their coterie or colony and attempt to join another (Garrett and Franklin 1988).

Intra-colony dispersal primarily through the movement of yearlings or adults from one coterie to another is relatively common in prairie dogs (Garrett and Franklin 1988; Hoogland 1995). A recent multi-year study of one Canadian prairie dog colony (Walker colony; Kusch et al. 2020) highlighted the influence of age, sex, and reproductive success on intra-colony dispersal. Kusch et al. (2020) noted that 84.4% of tagged prairie dogs at the Walker colony remained philopatric over a 12 to 24-month period, while 15.6% dispersed within the colony. Previous research has suggested that intra-colony dispersals are dominated by males (Garrett and Franklin 1988; Hoogland 1995). However, Kusch et al. (2020) found a roughly equal representation of male and female prairie dogs among the 43 dispersing individuals they monitored. Yearling dispersers were more likely to be male, but there was no sex difference observed among adult dispersers. All dispersals were observed in the weeks following pup emergence, and most adult females that moved from one territory to another (14/21) had recently experienced reproductive failure (Kusch et al. 2020). The average distances travelled within the colony were 315 m for adult females, 255 m for adult males, 215 m for yearling females, and 285 m for yearling males.

Inter-colony dispersal (for example, movement from a coterie in one colony to a coterie in a different colony) has not been studied in Canadian Black-tailed Prairie Dogs, but individuals have been observed travelling off colony both inside and outside Grasslands National Park (Liccioli pers. comm. 2022; Stephens pers. comm. 2022; Masefield Pasture Association Board pers. comm. 2023). Relatively long-range movements have been documented in the Park; for example, the South Gillespie colony was confirmed to have been recolonized two to five years after extirpation, despite being located approximately 8 km from the nearest active colony. Settlement of six new areas have been recorded in recent years within Grasslands National Park (see Distribution), and these range from approximately 2 to 4 km from the closest extant colony (Parks Canada unpub. data). The maximum straight-line distance between a Canadian colony and its nearest neighbour is less than 9 km, and most colonies are within 2 km of their closest neighbour (Parks Canada unpub. data). The straight-line distances travelled by inter-colony dispersers in South Dakota (ranging from 0.5 to 5.5 km; Garrett and Franklin 1988) suggest that Canadian colonies are within the dispersal capabilities of the species. However, potential movement corridors and/or barriers have not been identified within the Canadian distribution. Observations from other populations of Black-tailed Prairie Dogs suggest that individuals may follow ravines, canyons, dry creek beds, or other areas offering protection from predators, rather than travelling across wide open terrain (Garrett and Franklin 1988; Roach et al. 2001). Vegetation height and density at the periphery of or between active colonies may also influence the ease of dispersal or colony expansion. Cincotta et al. (1983) observed that colony expansion was most likely to occur at colony edges with the highest population density and the lowest height and density of vegetation. This apparent preference for expanding into habitats with low, sparse vegetation is further supported by controlled burn and brush removal experiments (for example, Milne-Laux and Sweitzer 2006) that demonstrate prairie dogs are more likely to venture into open, visually unobstructed areas.

Soper (1938) surmised that the Canadian population was established by prairie dogs advancing north along the Frenchman River Valley from colonies in Montana that otherwise remained below the Milk and Missouri rivers. Local knowledge from ranchers whose families have been in the area for generations suggest that Black-tailed Prairie Dogs were not observed in the 1800s and early 1900s (Masefield Pasture Association Board pers. comm. 2023). Appendix 2 reviews the recorded history of Black-tailed Prairie Dogs in Canada. The historical and pre-European distributions of Black-tailed Prairie Dogs are the subject of some debate in the literature, with authors suggesting that either smaller (Virchow and Hygnstrom 2002) or larger distributions and abundances (Knowles et al. 2002) existed in the past. While historical distributions are unknown, it is likely that increasing habitat fragmentation and land alteration over time have eliminated suitable dispersal corridors for Canadian prairie dogs, effectively isolating the population from their conspecifics in the U.S. There are no known records of dispersal between the Canadian and Montana populations. However, many local ranchers believe that Black-tailed Prairie Dogs use disturbed and cultivated land to their advantage (RM Val Marie pers. comm. 2024). Genetic analyses indicate that the Canadian population has low genetic variability and high inbreeding relative to other populations (Cullingham et al. 2023). Prairie dogs in Montana are more closely related to conspecifics in South Dakota than they are to those in Canada (Cullingham et al. 2023).

Interspecific interactions

Prairie dogs are considered to be ecosystem engineers for their role in shaping grassland ecosystems and creating habitat for other wildlife (Jones et al. 1994; Bangert and Slobodchikoff 2006; Davidson et al. 2012). The frequent disturbance of soil and clipping of vegetation by prairie dogs maintains open grassland habitat used by other mammals, as well as birds, insects, and herpetofauna.

Predators and competitors:

The Black-footed Ferret is an obligate predator of Black-tailed Prairie Dogs and its persistence in North America is dependent on healthy populations of prairie dogs. There are currently no Black-footed Ferrets remaining in Canada, but efforts to reintroduce this species to the country could resume in the future (see Special significance).

Swift Fox (Vulpes velox) and Prairie Rattlesnake are also known to prey on Black-tailed Prairie Dogs and use their burrows for denning. Other predators include American Badger (Taxidea taxus), Bobcat (Lynx rufus), Red Fox (Vulpes vulpes), Coyote (Canis latrans), Long-tailed Weasel (Neogale frenata), Bullsnake (Pituophis catenifer sayi), and a wide variety of aerial predators such as Cooper’s Hawk (Accipiter cooperii), Ferruginous Hawk, Red-tailed Hawk (Buteo jamaicensis), Swainson’s Hawk (Buteo swainsoni), Peregrine Falcon (Falco peregrinus), Prairie Falcon (Falco mexicanus), and Northern Harrier (Circus hudsonius).

Host/parasite/disease interactions:

Black-tailed Prairie Dogs are highly susceptible to sylvatic plague and local knowledge indicates that periodic disease acts to reduce the population when it is high (see Current and projected future threats).

Other interactions:

Black-tailed Prairie Dogs are primarily herbivorous. Their diet preferences tend to vary by colony locality and by the time of year (see Habitat requirements). As herbivores, Black-tailed Prairie Dogs significantly affect plant composition. Active prairie dog colonies are readily identified by mounds of soil piled next to burrow entrances and significantly altered vegetation structure (lower height and biomass) relative to surrounding areas (Wicker and Detling 1988; COSEWIC 2011; Davidson et al. 2012). The establishment of Black-tailed Prairie Dogs in a new, grass-dominated area can lead to a 60% to 80% reduction in plant biomass (above-ground net primary productivity), through both direct herbivory and wastage (Wicker and Detling 1988). Although the persisting vegetation on active prairie dog colonies is lower in biomass than in adjacent areas, grazing by prairie dogs has been observed to improve forage quality in some studies through enhanced plant nitrogen uptake (Coppock et al. 1983a; Wicker and Detling 1988). This effect has not been observed by local ranchers who report very little vegetation on colonies and no vegetation for grazing cattle (Masefield Grazing Ltd. pers comm. 2024). In some areas, the higher forage quality attracts large herbivores like cattle and bison which maintain low vegetation through their own grazing and promote high-quality forage growth through defecation (Coppock et al. 1983b; Davidson et al. 2012).

In Grasslands National Park, Burrowing Owl pairs are strongly associated with the colonies of Black-tailed Prairie Dogs and will use abandoned prairie dog tunnels for nesting and rearing young (COSEWIC 2011, 2017). Historical declines in Black-tailed Prairie Dog abundance have been followed by Burrowing Owl population declines in some parts of their range (Desmond et al. 2000).

Other species at risk that utilize habitat on prairie dog colonies include the Mountain Plover, Prairie Rattlesnake, Greater Short-horned Lizard (Phrynosoma hernandesi), and Swift Fox (Environment Canada 2006; COSEWIC 2011).

Physiological, behavioural, and other adaptations

Black-tailed Prairie Dogs are generally considered facultative hibernators due to their ability to enter torpor in response to resource shortages or other environmental stressors (as opposed to obligate hibernators, which respond to annual cues such as photoperiod; Lehmer et al. 2001). Consequently, there is considerable variation in hibernation frequency and phenology among populations of Black-tailed Prairie Dogs across their range.

Black-tailed Prairie Dogs in Canada are the only population known to consistently hibernate on an annual basis, and they generally do so between the months of November and February (Gummer 2005; Hawkshaw 2022). During the hibernation period, prairie dogs will enter multiple bouts of torpor, interspersed by periods of arousal, in which they may be seen above ground (Hawkshaw 2022; Wilder Institute/Calgary Zoo unpub. data). The frequency, timing, and duration of these bouts of torpor are variable and may be influenced by sex (Hawkshaw 2022), body condition (Hawkshaw 2022), and/or environmental conditions such as ambient temperature, drought, and winter severity (Kusch et al. 2021).

Different hibernation patterns may also be observed among populations, and even individuals living within a relatively small spatial area. Lehmer et al. (2006) examined six separate colonies in northern Colorado and observed that one population exhibited long, deep, and consecutive bouts of hibernation with brief periods of arousal, while the five others had intermittent, shallow bouts of torpor. This was demonstrated by greatly different patterns in overwinter body temperatures. The population with long periods of torpor had more widely ranging body temperatures with minima an average of eight degrees colder. While moderate genetic differences were detected between study populations, there was also evidence of a significant amount of dispersal between the colonies (Lehmer et al. 2006). All colonies were within a 25-km radius of one another. However, the population with long bouts of torpor received significantly less rainfall (relative to neighbouring colonies) during the growing season in years before, during, and after the winter period studied. Lehmer et al. (2006) concluded that this was evidence of extreme thermoregulatory plasticity in response to varying environmental conditions.

Seasonal torpor may also help prairie dogs conserve water, thus mitigating the risk of dehydration and death during severe drought. Bakko (1977) observed that Black-tailed Prairie Dogs in Montana and North Dakota survived longer and had a greater ability to concentrate their urine during drought periods than did the closely related White-tailed Prairie Dog (Cynomys leucurus) in Wyoming. White-tailed Prairie Dogs appeared to rely on seasonal hibernation to escape drought stress, whereas the Black-tailed Prairie Dogs were able to remain active year-round (Bakko 1977). Whether the Black-tailed Prairie Dogs in Canada have similar physiological adaptations to withstand drought stress is undetermined. Their drought-prone environment and variable survival following significant drought events (Stephens et al. 2018; Kusch et al. 2021) has presumably provided some selective pressure. It is likely that both physiological adaptations (for example, urine concentrating ability) and behavioural adaptations (for example, seasonal torpor) have facilitated the persistence of prairie dogs in southern Saskatchewan.

Limiting factors

Limiting factors are generally not human-induced and include intrinsic characteristics that make the species less likely to respond to conservation efforts. Limiting factors may become threats if they result in population decline. Limiting factors for Black-tailed Prairie Dogs in Canada consist of their reproductive phenology and low genetic diversity. Reproduction occurs prior to the growth of new grasses and forbs in the spring (a.k.a. “green-up”); therefore, adult females must rely on energy stores from the previous year to reproduce. A summer-autumn drought and severe winter can lead to reproductive failure (Kusch et al. 2021) and thus restrict population growth (see Threats, and Population sizes and trends). Local ranchers also observe that the combination of drought followed by severe winter will result in fewer animals but also point out the resilience of this species and adaptation to drought landscapes, which has allowed them to persist (Masefield Pasture Association Board pers. comm. 2023). Investigations into the genetic diversity of Canadian Black-tailed Prairie Dogs have found very low variability and high inbreeding (Cullingham et al. 2023). Low genetic diversity could limit the Canadian population through reduced reproductive fitness and elevated extinction risk (Spielman et al. 2004).

Population sizes and trends

Data sources, methodologies, and uncertainties

The size of Black-tailed Prairie Dog populations and consequently their temporal trends are difficult to quantify in absolute terms because densities can vary unpredictably within and between colonies and do not correlate with the density of burrows (King 1955; Campbell and Clark 1981; Hoogland 1981, 1995). Instead, population size and trends are commonly evaluated in relative terms by combining colony extent mapping with density estimates derived from visual counts. Colony extent mapping provides an estimate of the amount of area used by Black-tailed Prairie Dogs. Visual counts enumerate prairie dog individuals seen above ground in a fixed window of time and space to provide an index of population density. When used repeatedly, these two methods combined provide an index of relative abundance or population size over time. In addition, mark-recapture data can be used to estimate population density and vital rates (that is, reproduction and survival) and provide insight into the drivers of observed temporal trends.

All three forms of data are available for Canadian Black-tailed Prairie Dogs.

Colony extent mapping

Between 1993 and 2023, extents of Canadian Black-tailed Prairie Dog colonies were mapped 11 times (Figure 3). Methodology and data for these surveys are provided in the Extent of occurrence and area of occupancy section and in Table 1.

Visual counts

Between 1996 and 2023, 23 visual count surveys were conducted to estimate annual mean relative density of Canadian Black-tailed Prairie Dogs (Table 5; COSEWIC 2011; Parks Canada and Wilder Institute/Calgary Zoo unpub. data). Survey protocols generally followed recommendations by Menkens et al. (1990) and Menkens and Anderson (1993) and entailed multiple sessions of above-ground visual counts of adult and juvenile prairie dogs in 4-ha survey plots (200 m x 200 m). However, the number of survey sessions, the time of year, and time of day the surveys were conducted, the length of each session, the number of counts per session, and calculation of density estimates have varied across the years as resources and research or management priorities shifted (see Appendix 3 for details on the different methods). The total number and placement of plots surveyed have also varied across the years; thus, density estimates from all plots (that is, all plots surveyed in a given year, regardless of the site) and standardized plots (that is, only those plots that have remained consistent for multiple consecutive years) are used to calculate indices below (see Population size estimation) (Table 5).

Visual count data are best suited as a measure of relative rather than absolute density (Menkens et al. 1990; COSEWIC 2011). It can be difficult for observers to distinguish juvenile prairie dogs from Richardson’s Ground Squirrels or adult prairie dogs, particularly late in the active season (Stephens pers. comm. 2022). Consequently, visual count data are not useful for estimating age-specific densities, but they are useful for estimating total population densities. Additionally, these data are restricted to a subset of colonies within Grasslands National Park and may not be representative of the entire Canadian population. Great care needs to be taken when interpreting and making inferences from these estimates of population density given that visual counts were conducted on at most 2.79% of the total colony and may not adequately capture the heterogeneity within and between colonies.

Mark recapture

Mark-recapture studies are more resource intensive than visual counts and thus are used less frequently to estimate prairie dog population size and trends, and more commonly to address specific short-term research questions. Between 1999 and 2021, nine mark-recapture analyses were conducted on Black-tailed Prairie Dogs in Grasslands National Park (Gummer 2005; Lloyd 2011; Stephens 2012; Lloyd et al. 2013; Crill 2018; Stephens et al. 2018; Crill et al. 2019; Kusch 2018; Kusch et al. 2020, 2021; Hawkshaw 2022; Wilder Institute/Calgary Zoo unpub. data). In collaboration with Parks Canada, these studies were principally led by two institutions, the University of Saskatchewan (1999 to 2000; 2014 to 2020) and Wilder Institute/Calgary Zoo (2007 to 2021; in collaboration with the University of Calgary 2007-2009). Given differences in study design and research objectives, data from all nine studies cannot be pooled to assess population size and trends over the last two decades. However, a subset of the data from the Wilder Institute/Calgary Zoo (unpub. data; 2007 to 2016 and 2017 to 2019) was analyzed for comparison with the visual count dataset. Data and insights from the other mark-recapture research studies conducted in Grasslands National Park have been included in this report under the appropriate sections.

Study design and data analysis for the above-mentioned subset of data are based on the methods described in Stephens et al. (2018), with the following amendments: (1) data collection includes two additional years of data (2015 and 2016), and (2) the individual time-varying covariate of body mass class was removed from the RMark Robust Model used to estimate abundance and survival estimates for two age classes: juveniles and adults (yearling aged 1 year and adults aged 2+). Additionally, the total number and sites of colony plots sampled using mark-recapture methods have varied across the years. As is the case for visual counts, estimates from all mark-recapture plots combined are presented in Figure 4, along with those from standardized plots only (that is, only those mark-recapture plots that have remained consistent for multiple consecutive years).

Figure 4. Annual mean relative densities (total population) of Black-tailed Prairie Dogs (# prairie dogs/hectare) estimated from repeated visual count (VC) surveys and mark-recapture (MR) sessions on established prairie dog colonies between 1996 and 2023. The total number and locality of plots surveyed have varied across the years; thus, estimates from pooled plots (that is, “All Plots” – every plot surveyed in a given year, regardless of the locality) and a subset of standardized plots (that is, “Stnd 5 plots” or “Stnd 7 plots” - those plots that have remained consistent for multiple consecutive years) are presented here.

Population size estimation

As discussed above, there are no consistent/reliable long-term data to estimate the number and trends of mature prairie dogs in Canada. In the absence of these data, the relative mean total population density (from consecutive years of visual count density estimates, spanning approximately 7 generations) in combination with a “correction factor” derived from the proportion of adults to juveniles from mark-recapture data are used to approximate, with substantial caution, a range in mean annual population density of mature individuals (Figure 5).

Figure 5. Annual Black-tailed Prairie Dogs density estimates (# prairie dogs/hectare) for total population (yellow) and mature individuals (blue) using all visual count plots in Grasslands National Park from 2004 to 2023. Mature individual density estimates are calculated by multiplying the mean total population density by the upper and lower range of the proportion of adults in the population to the approximate range in the density of mature individuals in the population (see Population size estimation).

Population trends (total population density estimates) from mark-recapture data closely mirrored visual count estimates from 2007 to 2013; however, in 2014 they began to diverge and during this time there was a corresponding change in trapability of juvenile prairie dogs. Anecdotal observations by Wilder Institute/Calgary Zoo researchers suggest that juveniles and reproductively active females have been under-represented among trapped individuals since 2014. This was also reflected in the total population estimates obtained from mark-recapture data, which as of 2014 appear to be greatly underestimated relative to those obtained from visual count data (see Figure 4). For this reason, only adult to juvenile proportions from mark-recapture data between 2007 and 2013 were used to calculate the "correction factor" and apply it to visual counts to estimate population density of mature individuals.

An important note about this “correction factor”: understandably, the proportion of adults to juveniles in the population is lowest in years of population increase (years with high juvenile recruitment), and highest in years of population decline (low juvenile recruitment). For this reason, it was deemed unwise to apply the exact same “correction factor” to each year to estimate the density of adults in the population. Instead, the lower and upper range in mean proportion of adults during years of population increase (between 2007 and 2013: 0.491 to 0.768) and during years of population decline (between 2007 and 2013: 0.875 to 0.992) were calculated separately. The mean total population density estimate (visual count estimate) for each year between 2007 and 2023 was then classified as either increasing or decreasing relative to the previous year and multiplied by the corresponding correction factor to approximate ranges of mature adult density for each study year.

Multiplying these mature population density approximations by colony extents provides an index of mature individual population abundance. Given that colony extents were mapped approximately every other year from 2007 to 2023 with the exception of 2009, colony extents were approximated in the unmapped year by calculating the average extent of the two adjacent years (for example, colonies were not mapped in 2020, thus the average colony extent of 2019 and 2021 was used as a surrogate [Figure 6]). These data are also used to make inferences on population trends. All indices are calculated using both standard plots and all visual count plots (see Visual counts); however, only estimates derived from all plots are reported below in the Abundance and the Fluctuation and trends sections, unless the direction of the trend differs between standard and all plots, in which case both are reported. Great care needs to be taken when interpreting and making inferences from these approximations of mature population density and size, given the uncertainty in the proportion of juveniles in the population, the large heterogeneity in visual counts between colonies and sessions, and the small proportion of the total colony area sampled (at most 2.79%).

Figure 6. Estimates of Black-tailed Prairie Dog abundance for the total population (yellow) and for mature individuals (blue) in Grasslands National Park from 2007 to 2023. Total population abundance estimates were obtained by multiplying the mean total population densities of prairie dogs obtained from all visual count plots by the colony extent areas obtained for the corresponding year. In years when colony extents were not mapped (gray), the mean of the two adjacent years was used. The estimated range in mature individual abundance (lower = light blue, upper = dark blue) was calculated by multiplying the lower and upper estimates of the mature individual densities by the colony extents (mapped or average) for the corresponding year (see Population size estimation).

Population viability analysis

To support the development of the Canadian Black-tailed Prairie Dog Recovery Strategy and Action Plan, a structured population viability analysis (PVA) was performed to explore assumptions about the fundamental processes and relevant threats affecting the Canadian prairie dog population (Calgary Zoo Foundation and Grasslands National Park 2021 unpub. report). The PVA is a structured population model that tracks the number of individuals in each sex and stage-class (juvenile, yearling, adult) across colonies to estimate probability of persistence at the colony and total population level. Based on the assumption that the colonies of the Canadian prairie dog population function as a metapopulation, quasi-spatial structure is incorporated into the model in such a way that dispersal between colonies is represented as a function of distance between colonies. The PVA estimates the relative risk of extirpation while accounting for possible future scenarios involving two major threats to the Canadian prairie dog population: climate change and sylvatic plague (see Threats).

The model was implemented in the programming language R (R Core team 2008) and follows the methodology and theory outlined by McGowan et al. (2011), Lacy et al. (2013), and Morris and Doak (2002). It represents an improvement over the PVA (Stephens and Lloyd 2011) referenced in the previous COSEWIC report (COSEWIC 2011), given additional data and understanding of how the two main threats affect the vital rates of Canadian Black-tailed Prairie Dogs. The model parameters reflect best available knowledge from the literature, unpublished empirical data on Canadian Black-tailed Prairie Dog demography, and expert opinion gained through consultation with experts on prairie dog biology, climate change, or conservation planning (Calgary Zoo Foundation and Grasslands National Park 2021 unpub. report).

Climate change and sylvatic plague were incorporated into each PVA model as catastrophes by selecting one of four different scenarios per threat. The climate change scenarios are based on trends in drought conditions and include: “Drier Desert” (increasing drought-like conditions), “Status Quo” (relatively constant conditions), and “Oasis” (decreasing drought-like conditions) scenarios. The sylvatic plague scenarios are based on an increasing probability of an epizootic outbreak and two levels for the probability of plague spreading to any colony within 3 km of an already infected colony. The three plague scenarios are “Conservative (or Status Quo – lowest probability [0,005] of an outbreak and no probability of spread) , “Moderate” (medium probability [0.084] with some spread), and “Extreme” (highest probability [0.28] of an outbreak with some spread). In addition, a “Best Guess” scenario for each threat was generated based on expert biologist opinion (Calgary Zoo Foundation and Grasslands National Park 2021, unpub. report). In each iteration of the “Best Guess” model, one of the above scenarios is randomly selected based on a probability defined using expert opinion.

To represent the most likely trajectory of conditions in both threats that Canadian prairie dogs could experience over the next 50 years, an overall Best Guess–Best Guess model was run using the “Best Guess” climate and “Best Guess” plague scenarios. In the climate change “Best Guess” scenario, for each iteration, either the High or Low Carbon scenario is chosen based on a probability of 0.9 and 0.1, respectively. One of the 24 predictive climate models for that scenario is then randomly applied. In the “Best Guess” scenario for plague, for each iteration, one of the three scenarios is chosen based on a probability p (Conservative (p=0.5), Moderate (p=0.25), Extreme (p=0.25)).

An overall Status Quo–Status Quo scenario using the climate and plague “Status Quo” scenarios was also run to represent a future where both climatic and plague conditions remain relatively consistent in relation to present- day conditions. This model provides a baseline to compare the relative impacts of the overall Best Guess–Best Guess scenario.

All models were run over a 50-year time horizon (2017 to 2066) and used relative mean probability of metapopulation persistence as the measure of viability. The PVA was built as a stochastic simulation where parametric and process uncertainty are accounted for during the selection of vital rates. Each iteration is a forecast of the total number of animals over time. The model runs for 500 iterations per scenario (climate and plague scenarios) with up to 1,000 runs per iteration. The probability of extinction for each iteration is defined as the proportion of runs that go extinct in a given year (for example, in the 50th year). Probability of persistence is 1 minus probability of extinction; thus, each iteration yields one probability of persistence estimate with credible intervals estimated using a parametric bootstrap. A sensitivity analysis was not performed for the models.

Although evidence for projected declines of the mature prairie dog population is not available, the Status Quo–Status Quo and Best Guess–Best Guess models of the PVA do provide the best available quantitative analysis for insight into the relative probability of persistence of the total Canadian prairie dog population (juveniles and adults) under the most likely trajectory of climatic and plague conditions in the future.

Abundance

Direct estimates of Black-tailed Prairie Dog population size are not available for Canada. The best approximation of the total number of mature individuals in 2023 can be estimated using inferences from total colony extents (see Extent of occurrence and area of occupancy), mean visual count density estimates in 2023 (Table 5), and the upper and lower range of mean proportion of adults in the population (correction factor) during years of population decline from long-term mark-recapture data (correction factor for declining years: 0.875 to 0.992; Wilder Institute/Calgary Zoo unpub. data). The range in estimates of the mean proportion of adults in the population is taken from years of population decline, because mean visual count total population density estimates declined from 2022 to 2023, suggesting low juvenile recruitment (see Population size estimation). Using this rationale, the best estimate of the mature Canadian Black-tailed Prairie Dog population size in 2023 is 8,291 to 9,396 individuals (Figure 6). Great care needs to be taken when interpreting and making inferences from these approximations of population size, given the uncertainty in the proportion of juveniles in the population, the large heterogeneity in visual counts between colonies and sessions, and because visual counts were conducted on at most 2.79% of the total colony area.

Fluctuations and trends

Continuing decline^{Footnote 1} in number of mature individuals:

Given the difficulty obtaining estimates of mature individuals, there are no available data to directly assess fluctuations and trends in the number of mature prairie dogs in Canada. However, indices of mature individual population density and abundance (see Population size estimation) obtained since 2007 highlight the potential for the species to experience significant declines in a short period of time (single and multi-year), as well as the species’ ability to rebound (Figure 5; Table 6). At the time of the previous COSEWIC assessment (COSEWIC 2011), the species was experiencing an overall rapid decline in estimates of total number of mature individuals in the population (54% to 66% decline between 2007 and 2010). The trend continued with a decline of 62% (within 1 generation) resulting in the lowest documented population estimate to date of 2,567 to 2,909 mature individuals in 2013 (an overall estimated decline of 82% to 87% within 2 generations 2007 to 2013). The population experienced growth after 2013 (2017 population estimate: 22,114 to 25,062 mature individuals), and rebounded again from a subsequent crash in 2018 (estimated 208% increase from 2018 to 2021). In the most recent years (2021 to 2023) the population has experienced another estimated overall decline of 63% (Table 7; Figure 6). Observations over the time series of data available suggest that the declines between two selected time points are part of longer-term fluctuations and do not meet the criteria of a continuing decline in the number of mature individuals. Population viability analysis models that incorporate Best Guess scenarios for future threats of climate change and plague predict a significant decline in the relative mean probability of prairie dog persistence over the next two decades (Figure 7).

Figure 7. Relative probability of persistence estimates for the Canadian Black-tailed Prairie Dog metapopulation over 50 years for the Status Quo-Status Quo (that is Status Quo climate, Status Quo [Conservative]) plague) and Best Guess–Best Guess (that is Best Guess climate, Best Guess plague) scenarios. Each scenario was run for 500 iterations, with up to 1,000 runs per iteration. Grey shading depicts the 95% credible intervals.

Evidence for continuing decline (1 generation or 3 years, whichever is longer, usually up to 100 years):

Estimates of mature individual population abundance (see Population size estimation) suggest an overall decrease (33% to 52% decline) within the most recent generation (2020 to 2023) (Table 7; Figure 6). However, in the context of the full time series of estimates this decline could be part of natural fluctuations.

Evidence for continuing decline (2 generations or 5 years, whichever is longer, usually up to 100 years):

The estimated number of mature individuals in the population (see Population size estimation) over the two most recent generations declined (estimated 63% decline between 2017 and 2023). However, within this time period there is evidence that the population experienced two periods of decline and one multi-year population growth period. Therefore, the criteria for continuing population decline are not met (Table 7; Figure 6).

Evidence for past decline (3 generations or 10 years, whichever is longer) that has either ceased or is continuing (specify):

Although approximations of the number of mature individuals in the population provide evidence that the population has experienced two crashes, there is no evidence of continuing decline over the past 10 years. Instead, the approximations point to an overall increase of 223% from 2013 to 2022 followed by a decline in 2023 (Table 7; Figure 6).

Evidence for projected or suspected future decline (next 3 generations or 10 years, whichever is longer, up to a maximum of 100 years):

There are no analyses available for projected mature or total population size from the 2021 population viability analysis as the output is a probability of persistence (Calgary Zoo Foundation and Grasslands National Park 2021, unpub. report). In the Best Guess model (best guess for climate and plague scenarios) for 2033 (10 years from most recent estimate) the probability of persistence is approximately 0.7 with large credible intervals (approximately 0.1 to 1; Figure 7). The threat impact was assessed as Very high/High, which suggests a median decline of between 75% (Very high) and 40% (High)(Masters et al. 2021), over the next 3 generations or 10 years.

Extinction risk based on quantitative analysis:

The population viability analysis models suggest future declines in the relative mean probability of Black-tailed Prairie Dog persistence in Canada (Figure 7). Over the short term (that is, approximately the first 10 years of the modelling exercise from 2017 to 2027), the relative mean probability of persistence is high for both the Status Quo and Best Guess scenarios, with relatively low uncertainty in the estimates. This suggests there is little concern for the extirpation of the species in the immediate future. However, the relative mean probability of prairie dog persistence under each scenario begins to diverge between 2022 and 2042.

The Status Quo scenario suggests that there is a relatively low chance of prairie dog extirpation in Canada over the next 10, 20, or even 40 years with increasingly larger credible intervals (Figure 7). As stated earlier, this model is useful for putting the other scenarios into perspective, but it is not considered helpful for informing decisions, as the likelihood of current conditions continuing in the future could be quite low (Calgary Zoo Foundation and Grasslands National Park 2021 unpub. report).

The Best Guess scenario suggests that the combined impacts of climate and plague on prairie dog viability could lead to a relatively high risk of species extirpation in Canada within 40 years. Within the next decade (to 2032), the model predicts a nearly 20% decline in relative mean probability of persistence. This estimate is even lower in 2042, taking into account the 50% decline as of 2022. However, large credible intervals around the mean probability of persistence (approximately 0.1 to 1 at 2032 and beyond; Figure 7) reflect uncertainty in the input values (that is, knowledge or parametric uncertainty) and are a reminder of the uncertainty in our understanding of how the future is likely to unfold (Calgary Zoo Foundation and Grasslands National Park 2021 unpub. report).

Long-term trends:

At the time of the previous COSEWIC assessment (COSEWIC 2011), the species had experienced an overall decline in estimates of total number of mature individuals (54% to 66% decline between 2007 and 2010). In the intervening years, the population has experienced fluctuations, and an overall trend is difficult to determine (see Population fluctuations).

Population fluctuations, including extreme fluctuations:

Canadian prairie dogs have experienced fluctuations (of varying duration and intensity) in the approximated abundance and density of the mature population over the course of the last two decades. Nearly 5 generations fall within the 14 years of 2007 and 2023 and within this time frame, roughly 4 of the 5 generations experience a rapid population crash in a single year, followed by a rebound (2007 to 2008: 45% to 60% decline followed by a presumed rebound observed in mark-recapture data (see Figure 4); 2009 to 2010 decline followed by a rebound, both inferred from mark-recapture data see Figure 4); 2012 to 2013: 17% to 40% decline followed by 60% to 112% rebound in 2014; 2017 to 2018: 67% decline followed by a 38% to 91% increase; 2022 to 2023: 52% to 65% decline)(Table 7; Figure 6). These data support that Canadian prairie dogs do experience frequent and rapid fluctuations; however, unlike the dramatic decline of 82% to 87% observed between 2007 and 2013 (2 generations), which was greater than one order of magnitude, most of these rapid crashes and rebounds were all within one order of magnitude and might be better interpreted as normal fluctuations. Great care needs to be taken when interpreting and making inferences from these density estimates as the drivers contributing to annual increases and decreases in the density within the static plots cannot be teased apart; these include mortality of mature individuals, transition of individuals from the juvenile to mature age classes, reproductive rates, immigration and emigration, and the contraction and expansion of territories.

Severe fragmentation

Canadian Black-tailed Prairie Dogs do not meet the criteria for severe fragmentation. Although the population is considered isolated from the rest of the species’ range and its distribution is restricted within Canada (see Distribution), all colonies are presumed to be within dispersal distance of their nearest neighbour (see Movements, migration, and dispersal).

Rescue effect

There are no known outside source populations that provide immigrants to the Canadian population. The nearest Black-tailed Prairie Dog colony outside of Canada, a colony in Montana, is 20 km away, which is greater than the few dispersal distances recorded for the species (all <10 km; Garrett and Franklin 1988). This isolation is also supported by genetic evidence that did not identify recent migrants (Cullingham et al. 2023). Without human assistance via conservation translocations from either wild or captive sources, rescue in the case of the species’ extirpation from Canada is unlikely.

Habitat availability within the Canadian range is assumed to be both high and stable, given that a large portion of occupied habitat is within Grasslands National Park. Conditions are not deteriorating at present but may be threatened by increasing frequency and severity of drought over the medium to long-term (see Historical, long-term, and continuing habitat trends).

Threats

Historical, long-term, and continuing habitat trends

There are no historical data on Black-tailed Prairie Dog habitat quality and quantity. Based on the species’ current habitat requirements, it is assumed that the quantity of available habitat declined in tandem with European colonization and alteration of the Great Plains, and that this decline had already begun by the time the species was first documented in Canada (see Distribution). This perspective has been disputed as some authors suggest that the pre-European distribution was smaller (Virchow and Hygnstrom 2002). Prairie dogs in Canada may have persisted due to ranching activities that allowed natural prairie ecosystems to persist.

The recovery strategy (Parks Canada Agency 2021) defines Critical Habitat for Black-tailed Prairie Dogs as the maximum extent (dissolved polygons) of active prairie dog colonies documented between 2002 and 2019, which equates to a total of 1399.8 ha. Critical Habitat may be amended in the future within Grasslands National Park to allow for the expansion of existing colonies, recolonization of historical colonies, or establishment of new colonies. At present, the availability of potential habitat for prairie dogs is assumed to be stable within the Park. Thorpe and Stephens (2017) identified ~4,400 ha of habitat that may be suitable for prairie dog occupancy but does not yet host colonies. These areas are currently being evaluated using a habitat assessment index to capture characteristics that have yet to be included in statistical models, such as the presence of invasive species, the proportion of edible grasses and forbs, and the presence of plant species that may be indicative of high primary productivity (Parks Canada and Wilder Institute/Calgary Zoo 2021, unpub. report). It is assumed that the true amount of suitable habitat is considerably lower than 4,400 ha. Given the extent of existing farmland, the continued conversion of prairie to cropland and the low social acceptance of prairie dogs, opportunities for increasing prairie dog habitat outside the Park are limited.

Overall, the availability of prairie dog habitat over the medium to long term is expected to be threatened by the increasing frequency and severity of drought (see Droughts – IUCN 11.2, below). Moreover, habitat availability for expansion into unoccupied habitat may be limited by competing habitat needs of other species at risk, such as Greater Sage Grouse (Centrocercus urophasianus urophasianus).

Current and Projected Future Threats

The Black-tailed Prairie Dog is vulnerable to the cumulative effects of various threats, especially sylvatic plague and drought. The nature, scope, and severity of these threats has been described in the Threats Calculator in Appendix 1, following the IUCN-CMP (International Union for the Conservation of Nature – Conservation Measures Partnership) unified threats classification system (see Salafsky et al. 2008 for definitions and Master et al. 2012 for guidelines). The threat assessment process consists of assessing impacts for each of 11 main categories of threats and their subcategories, based on the scope (proportion of population exposed to the threat over the next 10-year period), severity (predicted population decline within the scope during the next 10 years or three generations, whichever is longer, up to ~100 years), and timing of each threat. The overall threat impact is calculated by taking into account the separate impacts of all threat categories and can be adjusted by the species experts participating in the threats evaluation.

The overall threat impact for Black-tailed Prairie Dogs is considered to be Very high - High. These values are to be interpreted with caution, as they may be based on subjective information, such as expert opinion, although efforts have been made to corroborate the scores with available studies and quantitative data.

Invasive and other problematic species and genes (IUCN 8.0; overall threat impact very high/high)

Invasive non-native/alien species/diseases – IUCN 8.1 (very high/high)

The bacterium that causes sylvatic plague, Yersinia pestis, was first detected in a Canadian prairie dog colony in 2010, but it had been reported in Saskatchewan as early as 1946 (Humphreys and Campbell 1947) and in Grasslands National Park in 1996 (Leighton et al. 2001). At the time of its discovery in the Canadian Black-tailed Prairie Dog population, the impact of sylvatic plague was already well documented in the U.S. where it has been a threat to prairie dogs since the mid-20th century (Cully and Williams 2001; Antolin et al. 2002; Parks Canada Agency 2021). Outbreaks of plague in the U.S. (that is, in an epizootic stage, with high prevalence and rapid spread) have resulted in 90% to 100% mortality rates on some infected prairie dog colonies (Cully and Williams 2001; Antolin et al. 2002; Stapp et al. 2004; Lorange et al. 2005), and colony extirpation is not uncommon (Cully and Williams 2001).

The transmission of sylvatic plague occurs primarily through bites by infected fleas (Cully and Williams 2001; Antolin et al. 2002; Eisen et al. 2006; Hinnebusch et al. 2017), which are readily circulated among social mammals like prairie dogs (Hoogland 1995; Biggins and Kosoy 2001). It is possible for the disease to persist in prairie dog populations at relatively low levels, with low overall mortality (that is, an enzootic stage; Hanson et al. 2007). Some individuals may also develop resistance to plague after an epizootic event (Rocke et al. 2012; Russell et al. 2019), but this has not been demonstrated in the Canadian population, and a variety of other factors such as genetic bottlenecks, body condition, and seasonal effects may ultimately influence disease resistance (Pauli et al. 2006; Tripp et al. 2009; Russell et al. 2019). Population recovery from an epizootic plague event may take many years; estimates from U.S. populations suggest 7 to 10 years is the norm (Cully and Williams 2001; Johnson et al. 2011), but as few as four and as many as 15 years between outbreak and recovery have been recorded (Augustine et al. 2008; Cully et al. 2010; Johnson et al. 2011). Recovery is likely facilitated by immigration (Cully and Williams 2001; Antolin et al. 2002) and high vital rates that often accompany low population density in this species (Cully and Williams 2001; Pauli et al. 2006).

Although there are many examples of population growth following epizootic plague events in the U.S. (Augustine et al. 2008; Johnson et al. 2011), the relative isolation of the Canadian population may make it especially vulnerable to extirpation after a wide-ranging epizootic. Conversely, the isolation of the Canadian population from other colonies may protect it from plague epizootics elsewhere in the species’ range, although this might be negated by contact with other species carrying the bacterium (for example, Richardson’s Ground Squirrels; Brinkerhoff et al. 2008; Liccioli et al. 2020).

To date, no mass die-offs or complete colony collapses in the Canadian population have been conclusively attributed to plague. Although plague was confirmed to be the cause of death for one prairie dog and two Richardson’s Ground Squirrels found on the Broken Hills colony in 2017, no subsequent plague outbreak was detected (Liccioli et al. 2020). In 2010, when plague was first detected in a Canadian colony (the Larson colony; Antonation et al. 2014), a relatively isolated, small colony (South Gillespie) was extirpated. Whether this extirpation was related to plague or other effects, such as drought conditions in 2009, is unknown. No Black-tailed Prairie Dogs, Richardson’s Ground Squirrels, or fleas were collected from this site. It was later confirmed to be recolonized in 2017 (Parks Canada Agency 2021). Plague-positive fleas were collected from prairie dog burrows on Dixon North-Hill colony in 2013, the same year it experienced a near complete collapse, but no plague-positive prairie dogs or ground squirrels were identified. Other colonies with plague-positive fleas detected to date include Monument A, Monument B, Dixon West, and Dixon South (Liccioli et al. 2020). Flea surveillance detected plague in a pool of fleas from Monument A in 2023, resulting in increased surveillance in conjunction with application of sylvatic plague vaccine bait (Parks Canada 2024). One Black-tailed Prairie Dog and two Richardson’s Ground Squirrels found dead at this site were tested; Yersinia pestis tests came back negative (Parks Canada 2024).

Liccioli et al. (2020) observed that relatively few fleas sampled from Black-tailed Prairie Dogs in Grasslands National Park between 2010 and 2017 carried Y. pestis (0.75%), and that flea abundance declined substantially from spring to late summer of each year. Despite the low prevalence of plague-carrying fleas, efforts to reduce flea abundance via insecticide application were correlated with increases in prairie dog abundance (Liccioli et al. 2020), suggesting that plague may influence mortality rates in the Canadian population. Liccioli et al. (2020) concluded that sylvatic plague likely persists at enzootic levels and may pose a greater risk after dry/drought years when flea loads may be higher (Eads et al. 2016), particularly for co-occurring Richardson’s Ground Squirrels (Liccioli et al. 2020). Drought years followed by wet years may be particularly problematic, as fleas benefit from humidity. A recent study investigating the interplay between climate conditions and plague in influencing the abundance of three different species of prairie dog (Cynomys spp.) compared annual change in prairie dog abundance between plots with and without application of deltamethrin dust, which reduces fleas (Biggins et al. 2021). In treated plots, visual counts of prairie dog abundance increased year-over-year with precipitation; in untreated plots where plague was not managed, increased precipitation instead had a negative effect on prairie dog abundance (Biggins et al. 2021).

To explore the potential impact of plague on the likelihood of persistence of Black-tailed Prairie Dogs in Canada, Wilder Institute/Calgary Zoo and Parks Canada recently modelled alternative plague scenarios using a population viability analysis model (Calgary Zoo Foundation and Grasslands National Park 2021, unpub. report). Three plague scenarios were defined based on an annual probability of epizootic plague outbreak per colony (shown in brackets): Conservative (AKA Status Quo) (0.005), Moderate (0.084), and Extreme (0.279). The survival rate of prairie dogs affected by plague was considered the same for all scenarios. The likelihood that plague would spread from one colony to colonies nearby (within 20 km) was zero under the Conservative scenario and 0.02 under the other two scenarios. In the absence of management activities, when climatic effects were held at current conditions (Status Quo), the mean probability of persistence over the first decade simulated (2017 to 2027) stayed consistently high under all plague scenarios. Under the Extreme plague scenario, the model indicated a steep decline in the mean probability of persistence beginning in the second decade, with estimates of persistence hovering around 5% to 10% from 2047 to 2066. Projections were more optimistic under the Moderate and Conservative scenarios, although credible intervals around persistence estimates were wide beyond the year 2030. The likelihood of Canadian Black-tailed Prairie Dogs facing an Extreme plague scenario is unknown, but this is certainly not impossible, given the severity of the outbreaks observed in the U.S. (Salkeld et al. 2016).

Outside Canada, plague has occurred at frequencies that limit population recovery between outbreaks. Prairie dogs in southern Phillips County, Montana, 150 km south of Grasslands National Park, have experienced multiple plague outbreaks beginning in 1992 (USFWS 2004). By the mid-1990s, more than 10,000 ha of occupied prairie dog habitat had been reduced by 80%. Periodic plague epizootics since then, and continuing through 2022, have prevented population growth to a level that comes close to the area occupied by prairie dogs pre-1992 (R. Matchett pers. comm. 2023).

Grasslands National Park has developed a plague management plan to mitigate the risks of epizootic outbreaks; however, implementation can vary with funding availability and there is local concern that the chemicals used to control fleas could have consequences for other species at risk directly or by reducing insect abundance (Masefield Pasture Association Board pers. comm. 2023). Local concern may translate into flea control being suspended. Consequently, the threat of epizootic plague to prairie dog persistence in Canada is considered Very high/High.

Climate change and severe weather (IUCN 11: overall threat impact high/medium)

Droughts – IUCN 11.2 (high/medium)

Drought is a significant driver of Black-tailed Prairie Dog population variability in Canada. Population declines have been observed in the years immediately following drought events and are attributed to decreased survival rates associated with a reduction in the quality and availability of forage (Stephens et al. 2018). Ranchers have observed that in years with a drought followed by a severe winter, mortality occurs during the winter months (Masefield Pasture Association Board pers. comm. 2023). Drought directly reduces vegetation biomass (Hoover et al. 2014), which in turn reduces prairie dog body mass and body condition (Hoogland 1995; Stephens et al. 2018; Kusch et al. 2021). A reduction in body mass or condition could have multiple consequences, from a decreased ability to thermoregulate during hibernation and lower overwinter survival, to increased susceptibility to ectoparasites or a reduction in female reproductive rates (Knowles 1987; Grassel et al. 2016; Stephens et al. 2018; Kusch et al. 2021; Parks Canada Agency 2021). For Canadian prairie dogs, Stephens et al. (2018) reported the proportion of reproductively active adult females to be low in years following drought events in the previous growing season (0.01 to 0.26) relative to years following non-drought years (0.54 to 0.87). This relationship was mediated by total precipitation and the number of growing degree days. If precipitation levels were low, the probability of an adult female being reproductively active declined as the number of growing degree days increased. The influence of growing degree days was absent/not detected in years with high precipitation levels (Stephens et al. 2018). Similarly, Kusch et al. (2021) documented the combined impact of drought and severe winter conditions on prairie dog vital rates in Grasslands National Park. They estimated the overwinter mortality of Black-tailed Prairie Dogs in one colony to be 85% following a drought and a severe, prolonged winter. They also observed that individuals emerged later from hibernation, had lower body mass, and failed to reproduce in the following year.

The negative impact of drought on survival and reproduction rates in turn leads to declines in population density. Stephens et al. (2018) estimated 54% to 70% proportional declines in density following drought years, regardless of whether the previous year’s estimates of density were high or low. As with sylvatic plague, there is the potential for droughts to occur at frequencies that could limit the ability of the population to recover.

The role that climate change may play in increasing drought events on the southern prairies is uncertain. Canada’s Changing Climate Report (Bush and Lemmen 2019) indicates that most of the country is expected to receive higher annual mean precipitation (7% and 24% increases by the end of the 21st century under low and high emission scenarios respectively); however, droughts and soil moisture deficits will likely increase in the southern prairies as higher mean temperatures increase transpiration to levels that exceed summer precipitation (Bush and Lemmen 2019). There is an anticipated increase in frequency and severity of droughts in the prairies (PaiMazumder et al. 2013; Bonsul et al. 2020; Sauchyn et al. 2020). Ultimately, it is difficult to uncouple the impacts of drought and temperature extremes as these climatic events are intrinsically linked (see Threat 11.3 Temperature extremes).

The population viability analysis developed by Wilder Institute/Calgary Zoo and Parks Canada (Calgary Zoo Foundation and Grasslands National Park 2021, unpub. report) explored the influence of climate change on Black-tailed Prairie Dog persistence over a 50-year period. Under a “Status Quo” baseline climate scenario (that is, climate conditions remain consistent with current day conditions), mean probability of persistence remained around 70% to 75% over the next 50 years (2066). However, relative to the baseline model, the mean probability of persistence declined gradually over time under a “Best Guess” scenario (that is, the most likely climate change scenario given best available knowledge) to a low of ~28% in 2066. Despite the uncertainty in model estimates (represented by large credible intervals), the past, current, and likely future occurrence of drought and its population-wide impacts was assessed to pose a High/Medium threat to Black-tailed Prairie Dogs persistence in the Canadian range.

Temperature extremes – IUCN 11.3 (unknown)

There is considerable uncertainty around the impact of rising frequency of temperature extremes on Black-tailed Prairie Dogs in Canada, as well as the likelihood and nature of those extremes. Prolonged periods of extreme heat during the active season may trigger drought events and thus have a negative impact of prairie dog survival and reproduction (see Droughts – IUCN 11.2). Unusually warm winters may also have a negative impact on survival, because warm temperatures may increase arousal (and thus metabolic rates) during a time when food resources are limited (Parks Canada Agency 2021). Extremely cold temperatures during winter may have a more nuanced impact. Severe winters have been associated with increased over-winter survival and reduced reproduction rates in Canadian prairie dogs (Stephens et al. 2018), but with lower over-winter survival of prairie dogs in Utah (Hoogland 2006). Stephens et al. (2018) speculate that the metric they used for winter severity was a winter temperature index and suggest that a variable including temperature and snowpack might better explain the relationship. Landowners have observed that severe winters following dry years reduce population numbers, supporting the response observed in Utah (Masefield Pasture Association Board pers. comm. 2023). The differing results may be mediated by the insulative effects of the snowpack or group thermodynamics that are not fully understood (for example, Patil et al. 2013). Following a major drought and a prolonged, severe winter, prairie dogs at the Walker colony (in Grasslands National Park) emerged from hibernation approximately one month later in 2018 than they did in the previous three years (Kusch et al. 2021) and failed to reproduce entirely that year. This colony also had an estimated 85% over-winter mortality rate (Kusch et al. 2021). Given the likely confounding effects of drought, temperature extremes, deep snowpack, and late snowmelt, it is difficult to identify which variables influence survival and reproduction, and at which thresholds.

Storms and flooding – IUCN 11.4 (unknown)

Anthropogenic climate change is expected to increase the frequency of daily extreme precipitation events (Zhang et al. 2019), which may lead to periods of intense flooding. Relatively sudden, heavy precipitation has the potential to flood prairie dog burrows and erode dehydrated soils.

Most of the Black-tailed Prairie Dog colonies in Canada are located within the floodplain of the Frenchman River and are vulnerable to being inundated during periods of extremely heavy rain and/or in the event of a dam breach. The impact of storms and flooding on mortality and reproduction is unknown but could vary not only with the intensity but also the timing of the events (for example, during the spring, prior to the first emergence of pups). Instances of flooded (or collapsed) burrows were observed by Parks Canada and Calgary Zoo staff in 2011 and 2016, but the impact of these events on prairie dog survival could not be estimated.

Natural system modifications (IUCN 7; overall threat impact unknown)

Other system modifications – IUCN 7.3 (unknown)

Invasive plants can reduce native species abundance and richness (Andreu and Vilà 2011), and their presence in prairie ecosystems may facilitate further plant invasions through the modification of soil microbiota (Jordan et al. 2008). Presumably, a reduction in the abundance of native plant species could decrease overall forage quality for prairie dogs. In Grasslands National Park, invasive plants such as Crested Wheatgrass (Agropyron cristatum) and Yellow Sweet Clover (Melilotus officinalis) can also establish large monocrops, which increase vegetation height in and around prairie dog colonies and are hypothesized to impede colony expansion or increase predation rates. However, this is likely not a threat as local observations indicate that Black-tailed Prairie Dogs select these grasses because they green up earlier than some other native plants (RM Val Marie pers. comm. 2024).

Crested Wheatgrass was introduced to North America in the 1920s to supplement livestock forage during periods of drought (Rogler and Lorenz 1983). It is a hardy, cold-tolerant bunchgrass which grows to heights of 30 to 90 cm (USDA 2000), often in monotypic stands (McWilliams and Van Cleave 1960). Yellow Sweet Clover was introduced to North American grasslands in the mid-1800s to improve soil stabilization and nitrogen content (Wolf et al. 2003, 2004) and to serve as livestock forage (Turkington et al. 1978; Parks Canada Agency 2021). It can reach heights up to 300 cm (Wolf et al. 2003, 2004). Both Crested Wheatgrass and Yellow Sweet Clover can alter soil characteristics and restrict native species growth (Dormaar et al. 1995; Wolf et al. 2003, 2004). Both species have been confirmed on and around prairie dog colonies in Grasslands National Park and Masefield community pasture.

Although Black-tailed Prairie Dogs can clip vegetation (Ponce-Guevara et al. 2016; Connell et al. 2018) to improve their ability to detect predators (Hoogland 2006), habitat occupancy analyses have indicated that prairie dogs are generally averse to habitats with tall vegetation; their occupancy is inversely correlated with vegetation height (Collins and Lichvar 1986; Franklin and Garrett 1989; Guenther and Detling 2003; Avila-Flores et al. 2010; Breland et al. 2014). However, the degree to which Crested Wheatgrass or Yellow Sweet Clover may inhibit prairie dog habitat use is unclear. Local knowledge of individual prairie dogs establishing burrows in areas dominated by these invasive plants suggests that they are not deterred by their presence (Masefield Pasture Association Board pers. comm. 2023; RM Val Marie pers. comm. 2024). The habitat disturbances that facilitate Crested Wheatgrass or Yellow Sweet Clover expansion may also assist prairie dog dispersal and the establishment of new colonies within and beyond the Park (Parks Canada Agency 2021; Masefield Pasture Association Board pers. comm. 2023).

Biological resource use (IUCN 5; overall threat impact unknown)

Hunting and collecting terrestrial animals – IUCN 5.1 (unknown)

Incidents of prairie dog poisoning and shooting are suspected to occur outside of Grasslands National Park; however, these instances have not been confirmed. The provincial Black-tailed Prairie Dog Control Policy was implemented by the Saskatchewan Ministry of Environment on August 31, 2023 (to November 31, 2025) and outlines lethal (shooting) and non-lethal options to control the expansion of Black-tailed Prairie Dog colonies. The province has jurisdiction under The Wildlife Act, 1998 to issue permits for lethal (shooting) control of Black-tailed Prairie Dogs. Unintended indirect prairie dog mortality could also occur in association with the legal poisoning of other species such as Richardson’s Ground Squirrels.

Number of threat locations

All prairie dogs in Canada are found within a geographically distinct area and could be equally threatened by a single event (for example, plague or drought); therefore, they are considered to exist in one location. Although some colonies are spatially distant from others, genetic evidence shows little differentiation among colonies. This suggests that high levels of connectedness support a single location that could be rapidly affected by a plague outbreak. In addition, plague can be moved across the landscape by other species, further connecting colonies into a single location. An epizootic plague event has the potential to greatly reduce prairie dog abundance and lead to colony collapse. Weather related factors like severe drought coupled with harsh winters can have a similarly devastating effect on prairie dog abundance, and impact all colonies simultaneously (see Current and projected future threats).

Protection, status, and recovery activities

Legal protection and status

The Black-tailed Prairie Dog is currently listed on Schedule 1 of the Federal Species at Risk Act (SARA) as Threatened. COSEWIC first assessed the species in April 1978 and assigned a designation of Special Concern. Reassessments were done in April 1988, April 1999, and November 2000, confirming Special Concern status based on small population size, isolation, and risk of sylvatic plague. The status of the Black-tailed Prairie Dog was uplisted to Threatened in November 2011 based on increased threat of drought and sylvatic plague (Criteria D2).

Black-tailed Prairie Dogs receive protection federally under SARA and the Canada National Parks Act (CNPA). A recovery strategy and action plan for this species was posted in 2021 and estimates Critical Habitat at 1,399.8 ha, corresponding to the maximum extent of active colonies documented between 2002 and 2019 (Parks Canada Agency 2021). Critical habitat in Grasslands National Park is protected under the CNPA. Active monitoring for population trends, colony extents, and sylvatic plague surveillance is being conducted. All colonies in which Critical Habitat is identified are currently active and occupied.

Black-tailed Prairie Dog habitat on Saskatchewan’s agricultural Crown lands is protected through agricultural Crown lease agreements, policies and applicable acts and regulations, including The Provincial Lands Act, 2016; The Provincial Lands (Agriculture) Regulations; The Wildlife Act, 1998; and The Wildlife Regulations, 1981. One colony is also provincially protected under The Wildlife Habitat Protection Act, 2018.

Non-legal status and ranks

The Black-tailed Prairie Dog is classified on the IUCN Red List as Least Concern globally. NatureServe ranked it as G4 globally (Apparently Secure), and as N2 (Imperilled) nationally, and S2 (Imperilled) in Saskatchewan.

Land tenure and ownership

Approximately 94% of known Critical Habitat for the Black-tailed Prairie Dog in Canada is located within the proposed boundary of Grasslands National Park and is therefore under federal protection. With regard to the identified Critical Habitat on provincial agricultural Crown land, approximately 5.6% is leased by pasture associations (patron-managed groups) and approximately 1.1% is leased by an individual (Parks Canada Agency, 2021). National parks and other conservation areas often take advantage of stewardship practices that have helped preserve intact ecosystems and delineate them to function as refuges for a growing number of endangered species in Canada. This process and subsequent decisions about how to best manage the protected habitat for the conservation of those species are increasingly complex (Dietz et al. 2021).

Recovery activities

The Black-tailed Prairie Dog Recovery Strategy and Action Plan were published in 2021 (Parks Canada Agency 2021). The recovery strategy identifies Critical Habitat for the species as well as opportunities for more research and for refining definition and location.

Since the previous COSEWIC report, several research studies have been conducted on the ecology and population dynamics of Canadian prairie dogs which have contributed to the development of the Grasslands National Park Multi-species Action Plan (Parks Canada 2016b), and the population viability analysis (Calgary Zoo Foundation and Grasslands National Park. 2021). These studies have also helped to inform the Black-tailed Prairie Dog Recovery Strategy and Action Plan (Parks Canada 2021), and include:

• population-level research conducted by the Wilder Institute/Calgary Zoo in collaboration with Grasslands National Park focusing on drivers of population dynamics and on population genetics
• individual-level research conducted by the University of Saskatchewan (Dr. Jeff Lane) to better understand demographic rates, sociality, hibernation, and life history patterns
• the development of a habitat assessment tool to help identify priority sites for promoting colony expansion or restoration

In accordance with the Black-tailed Prairie Dog Management Plan (Tuckwell and Everest 2009) and the Grasslands National Park Multi-species Action Plan (Parks Canada 2016b), the following recovery actions have been implemented:

• the development and implementation of the Plague Mitigation Action Plan (Parks Canada 2011) including a plague surveillance program, preventative burrow dusting, and distribution of oral vaccine baits as well as emergency response dusting. A revised Plague Management Plan was developed in 2020, to reflect the most recent knowledge acquired on plague transmission ecology in the U.S. and Canada (Liccioli pers. comm. 2023)
• management strategies to improve historical prairie dog habitat through the removal of non-native and invasive alien plant species, the reduction of vegetation height, and increase in native plant density
• ongoing discussion with ranchers, species experts, and governmental organizations, to identify shared management objectives and recovery actions for the species
• a first draft policy led by the Saskatchewan Ministry of Environment in consultation with local landowners and stakeholders to mitigate conflict between landowners and prairie dogs

The wide variety and complexity of relationships between stakeholders, including the provincial and federal governments, local landowners, and other community members, may at times be challenging to navigate when there are differing perspectives and priorities. Local landowners have expressed concerns that conservation and management actions intending to protect prairie dogs may limit agricultural producers’ control over private lands and restrict ranching operations (Lamb et al. 2006; Liccioli pers. comm. 2023; Masefield Pasture Association Board pers. comm. 2023; RM Val Marie pers. comm. 2024). Developing and maintaining communications and engagement amongst stakeholders will play a key role in conservation of the Black-tailed Prairie Dog.

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Collections examined

No collections were examined for the preparation of this report.

Authorities contacted

Fargey, P. Provincial Species at Risk Specialist. Alberta Environment and Parks, Edmonton, Alberta

Grant, B. Local Stakeholder. Val Marie, Saskatchewan.

Kieth, J. Coordinator. Saskatchewan Conservation Data Centre. Regina, Saskatchewan.

Lane, J. Associate Professor, Department of Biology, University of Saskatchewan. Saskatoon, Saskatchewan.

Liccioli, S. Wildlife Ecologist. Grasslands National Park, Species At Risk Scientist, Nature Legacy Program. Val Marie, Saskatchewan.

Heisler, L. Wildlife Ecologist. Government of Saskatchewan, Ministry of Environment. Swift Current, Saskatchewan.

Petersen, S. Director, Conservation and Research, Assiniboine Park Zoo – Assiniboine Park Conservancy, Winnipeg, Manitoba.

Poulin, R. Head of Research and Collections, Research Scientist – Curator of Zoology Royal Alberta Museum. Regina, Saskatchewan.

Prieto Diaz, B. Terrestrial Ecologist. Government of Saskatchewan, Ministry of Environment. Regina, Saskatchewan.

Rand, G. Assistant Collection Manager, Vertebrate Zoology. Canadian Museum of Nature. Ottawa, Ontario.

Tuckwell, J. Species Conservation Specialist. Parks Canada. Winnipeg Manitoba.

Wu, J. Scientific Project Officer ATK. Environment and Climate Change Canada. Gatineau, Quebec.

Acknowledgements

Funding for the preparation of this report was provided by Environment and Climate Change Canada. The following authorities provided valuable data and/or advice: Joanne Tuckwell, Stefano Liccioli, Pat Fargey, Heather Facette, and Brett Grant. Natasha Lloyd, Jasmine Louste-Fillion, Rebecca Stanton, Tracy Hillis, Savita Owens-Frank, and Jordin Parder provided editorial and formatting assistance. The Rural Municipality of Val Marie and local ranchers were kind enough to share their time with several COSEWIC members including the TMSSC Co-chair in the spring of 2023.

Biographical summary of report writer(s)

Tara Stephens is a Conservation Population Ecologist at the Wilder Institute/Calgary Zoo. She holds a B.Sc. in Biological Sciences from University of Guelph and studied Black-tailed Prairie Dog habitat and population dynamics for her M.Sc. at the University of Calgary. Tara has led the Canadian Prairie Dog Ecosystem Research Project in collaboration with Parks Canada since 2010. Tara is a member of the Great Plains Conservation Network and the USFWS Black-footed Ferret Conservation Sub-Committee.

Kelly Swan is a Conservation Research Associate at the Wilder Institute/Calgary Zoo. She completed a B.Sc. in Zoology at the University of Toronto, an M.Sc. in Biology at the University of Victoria, and has over 18 years of experience conducting wildlife research for government, non-profit organizations, and academic institutions. She currently provides writing and research support to the Canadian Prairie Dog Ecosystem Research Project and the Vancouver Island Marmot project.

Jana McPherson is Senior Manager, Community Conservation at the Wilder Institute/Calgary Zoo. She holds a B.Sc. in Applied Biology from the University of Leeds, a Ph.D. in Zoology from the University of Oxford, and conducted postdoctoral studies at Dalhousie University which focused on documenting human impacts on species distributions. Her current work concerns the benefits and efficacy of community-based conservation, and the contributions local and traditional ecological knowledge can make to conserving imperilled species.

Appendix 1. Threats calculator for Black-tailed Prairie Dog

Threats assessment worksheet

Species or Ecosystem Scientific name:

Black-tailed Prairie Dog (Cynomys ludovicianus)

Date:

10/24/2022

Assessor(s):

Dave Fraser (facilitator), L. Gillis, M. Curteanu, T. Calteau, C. Cullingham, L. de Forest, P. Jayarajan, M. Ranalli, S. Liccioli, A. Patmanathan, J. Kusch, T. Stephens, S. Petersen

Assigned Overall threat impact:

AB = Very high - High

Overall threat comments:

Threat from outbreaks of sylvatic plague and increased risk of drought due to climate change are most important.

Appendix 2. Historical Canadian range and recent Canadian range

Historical Canadian range

The first written report confirming the existence of Black-tailed Prairie Dogs in Canada was published in 1938 (Soper 1938). Soper (1938) found no trace of the species in southern Alberta but did confirm a colony in southern Saskatchewan. The colony, which had reportedly come into existence 5 years prior, was located on the Prescott ranch in the Frenchman River Valley, 6 miles north of Val Marie. Construction of the Val Marie reservoir in 1937 completely submerged that prairie dog town. Several other colonies in the Frenchman River Valley reported to Soper in 1927 (and subsequently to the National Museum of Canada), however, have continued to persist to this day despite being unsubstantiated at the time (Table 1). Soper (1938) suggested that the species likely occurred at least intermittently throughout the 98 miles of Frenchman River Valley from the colony on Prescott ranch south to the forks of the Missouri and Milk rivers. At the time, these two rivers were seen to roughly define the species’ northern range limit in the U.S. (Anderson 1928 cited in Soper 1938). Several early observations of prairie dogs beyond the Frenchman River Valley were also reported but not substantiated, including a small prairie dog town a few miles south of Supreme near Battle Creek and an individual prairie dog sighted approximately 12 miles south of Cadillac (Soper 1944).

The next written record dates to 1961, when the Director of the Wildlife Branch, Department of Natural Resources, Regina, conducted a survey in response to ranchers’ concerns in the Val Marie area regarding the spread and establishment of new prairie dog colonies ruining their range (Paynter 1963). At the same time, the Natural Historical Society suggested that prairie dogs should be given protected species status in Canada (Paynter 1963). Paynter (1963) identified 9 main colonies and confirmed the presence of “several smaller colonies” that were not included in the report. Six of the reported colonies were located within the general vicinity of colonies that persist today (Table 1). Paynter (1963) recommended that the government neither protect nor exterminate the species. At the time, only the Dixon Community Pasture colony was protected, based on an agreement with the Department of Agriculture.

In 1966, an assessment of the Val Marie-Killdeer region for the potential creation of a Prairie Park included site visits and interviews with local ranchers to gather information on the historical and existing distribution of the Canadian Black-tailed Prairie Dog population (Stelfox 1966). Stelfox (1966) confirmed 6 of the 9 colonies previously reported by Paynter (1963), as well as 3 more colonies reportedly established in 1950, and 3 new colonies reportedly established in 1964. In addition, Stelfox also acquired information on two additional colonies east of the Frenchman River Valley near McEachern Creek (Township 1 Range 8) and Horse Creek (Township 1 Range 6) that were reported to have existed prior to 1912, both close to what is now the East Block of Grasslands National Park.

Based on these historical observations, it appears the Canadian distribution of Black-tailed Prairie Dogs was never as vast or densely populated as in the U.S. However, Anderson et al. (1986) report historical records of Black-footed Ferret (Mustela nigripes) specimens within and beyond the Frenchman River Valley. If Black-footed Ferrets in Canada were reliant on prairie dogs as a primary prey source as in other parts of their range, this would suggest the historical distribution of the Canadian Black-tailed Prairie Dog (that is, prior to ferret extirpation in 1937) was much broader than existing records would suggest.

Recent Canadian range

Between 1970 and 1985, the size and distribution of the Canadian Black-tailed Prairie Dog population was mapped in three separate studies (Table 1). The first study was conducted in 1970 by the Department of Natural Resources, Regina, during Greater Sage-Grouse (Centrocercus urophasianus urophasianus) and Pronghorn (Antilocapra americana) investigations in the Val Marie area (Kerwin and Scheelhasse 1971). Two other studies, conducted in 1975 and 1985, were a component of feasibility assessments undertaken to determine the suitability of the proposed Grasslands National Park (West Block) as a Black-footed Ferret reintroduction site (Millson 1976; Laing 1986).

Across the three studies, a total of 17 individual colonies were mapped (1970: n =15, 1975: n =13, 1985: n =14), 10 of which were located in the vicinity of historically documented colonies (Table 1) (Soper 1938, 1941; Paynter 1962; Stelfox 1966). Of the 15 colonies mapped in 1970, seven were ostensibly new colonies (Kerwin and Scheelhasse 1971), three of which effectively extended the previously documented range of the Canadian Black-tailed Prairie Dog population westward into the uplands (Timbergulch colony), southwest into the Masefield Community Pasture (Masefield colony) and southeast along the Frenchman River Valley toward the Montana border (South Gillespie) (Figure 2). South Gillespie, which was poisoned in 1970, and two small colonies located centrally in the range (South Belza 1 and South Belza 2) were the only colonies documented in 1970 that were not located in subsequent surveys in 1975 and 1985. In 1975, Millson (1976) found one new colony, a satellite colony adjacent to Masefield, which has not been recorded since. Laing (1986) reported two “new” colonies which aligned with two historical colonies: Broken Hills, first documented in 1961, and Dixon South colony, first recorded in 1927 but likely mapped as part of Dixon Southwest by Kerwin and Scheelhasse (1971) and Millson (1976).

With the exception of Millson (1976), who mapped colonies using physiographic features and calculated area by using planimetry and by overlaying a 1-centimetre grid, neither search effort nor mapping methodology were adequately reported. Consequently, comparison of the number and size of colonies between years may be unreliable. Acknowledging potential differences in effort and methodology, for the 12 colonies documented in both 1970 and 1975, the total area occupied increased from 501 ha to 763 ha, with an increase in average colony size from 33.5 ha to 58.6 ha (Millson 1976; Laing 1986). By 1985, the total area occupied appeared to have declined from 763 ha to 650 ha with a substantial decrease in the average area occupied by the larger colonies (from 187 ha to 60 ha) yet an increase in the smaller colonies (from 5.9 ha to 36 ha) (Laing 1986). The reasons for the apparent overall decline are unknown but are thought to have occurred prior to the species receiving legal protection in 1981. The decline may have resulted from a combination of factors such as control measures implemented by landowners, grazing pressure, and/or drought (Gauthier and Boon 1994; Harris 1995), but differences in sampling protocols may also have contributed.

With the establishment of Grasslands National Park between 1981 and 1988, the distribution and abundance of the Black-tailed Prairie Dog population in Canada were expected to increase beyond 1975 estimates. In 1992, Parks Canada recognized the need to assess the population’s response to land-use changes and to monitor the population to inform management of the species (Gauthier and Boon 1994). Consequently, Gauthier and Boon (1994) initiated standardized monitoring of the size and distribution of colonies in Grasslands National Park in 1992, and in the Community Pastures in 1993. In 1994 and 1995, Harris (1995) used the same methodology to complete the survey by mapping the remaining colonies located on privately operated agricultural lands. In both studies, colonies were located using information from previous studies as well as conversations with Park’s staff and ranchers. The perimeters of the colonies were mapped by walking from one active burrow to the nearest active burrow along the outermost area of the colony. A GPS (global positioning system) was used to record the site for each active burrow defining the perimeter. The data were imported into ArcInfo GIS (geographic information system) software to generate maps and calculate the area of each colony. Since the initial 1992/1993/1994 studies, surveys have been conducted approximately every other year to date (Table 1). To ensure comparability, the methodology developed by Gauthier and Boon (1984) has been used, with minor revisions based on improvements in technology and understanding of the systems.

Appendix 3. Visual count survey methods

For most visual counts prior to 2007, the season during which they were undertaken is unknown. In 2007 a long-term mark recapture study began on 5 of the visual count plots and was extended to 8 plots in 2010 (Table A1: represented in bold). Visual count surveys were conducted immediately following the mark recapture session for these plots; their timing thus varied across the field season (spring, summer, fall) but was consistent year-to-year for each plot. Beginning in 2013, visual counts have been standardized to the month of June (Grasslands National Park 2020). Between 2013 and 2016, each of the 8 above-mentioned plots were surveyed both in the standardized spring session as well as following the mark-recapture session (post MR) to assess if time of year affected density estimates and to help calibrate the 2007 to 2016 dataset with future data.

In addition to some variation in survey protocols, density estimates were calculated in two different ways across the survey years. For 1996 to 1999 surveys, density estimates were calculated per plot by summing the maximum number of juveniles and the maximum number of adults recorded separately over the four survey sessions and dividing the total by 4 ha (pdogs/ha). Since 2004, density estimates for each plot have been calculated using the maximum prairie dog count (juveniles plus adults in the same time interval) recorded across the three days and dividing it by 4 ha. Although juveniles and adults are recorded, only total density estimates are used due to potentially large observer bias and uncertainty in distinguishing between juvenile and adult prairie dogs.