Great Plains Toad (Anaxyrus cognatus): COSEWIC status report addendum Canada 2023

Offical title: COSEWIC Status Report Addendum for the Great Plains Toad Anaxyrus cognatus in Canada 2023

Committee on the Status of Endangered Wildlife in Canada (COSEWIC)
Special concern 2023

COSEWIC assessment summary

Assessment summary – May 2023

Common name: Great Plains Toad

Scientific name: Anaxyrus cognatus

Status: Special Concern

Reason for designation: This long-lived burrowing toad is patchily distributed across the southern Canadian prairie provinces. Spending most of its life underground, it emerges sporadically to feed and relies on small ephemeral water bodies to breed. Loss and degradation of habitat, particularly from changes in water management and agricultural land use, continue to impact this species. It is also vulnerable to increasing frequency and extent of drought linked to climate change. This reduces availability of already-restricted breeding sites both directly by lack of precipitation and indirectly by altering water management regimes, leading to recruitment failure and more pronounced population fluctuations.

Occurrence: Alberta, Saskatchewan, Manitoba

Status history: Designated Special Concern in April 1999. Status re-examined and confirmed in May 2002 and April 2010. Status re-examined and confirmed in May 2023.

COSEWIC addendum

Preface

There has been an increase in survey effort for Great Plains Toad since the previous assessment, from 2010 to 2019. Notably, these surveys increased the number of records in western Saskatchewan (Great Sandhills region), southeastern Saskatchewan, and southwestern Manitoba (near Melita). As a result of these surveys, both IAO and EOO have increased. These changes reflect an increased knowledge of the species’ distribution rather than an actual change in occupancy.

Two management plans have been published since the previous assessment, one for Alberta (Alberta Environment and Parks 2015) and one for Canada (Environment Canada 2013). These plans identified the following threats: pesticide and fertilizer applications, excessive livestock grazing, oil and gas development and operations, mortality from traffic, epidemic disease and parasites, and persistent drought, possibly to be exacerbated by climate change. Threats from dams, water management, agriculture, and climate change have particularly increased for this species since the previous assessment. The Prairie Farm Rehabilitation Administration (PFRA) program, which helped to sustain cattle-grazing lands and promoted soil and water conservation in Alberta, Saskatchewan, and Manitoba, was cancelled in 2009. Loss of this program may result in degradation of Great Plains Toad habitat, although, with no apparent intent by landowners to change land management practices, immediate impacts on Great Plains Toad are probably limited. In addition, there is strong evidence that Great Plains Toad is highly vulnerable to climate change. Increasing frequency and extent of droughts are expected to negatively impact the restricted breeding habitat of Great Plains Toad, leading to recruitment failure and more pronounced population fluctuations.

Both management plans recommend the following actions: improve monitoring of the species’ distribution and abundance, promote targeted stewardship activities, increase public involvement in the species’ conservation through outreach and communication, provide habitat protection through Beneficial Management Practices (BMPs), and address additional information requirements through research.

Executive summary

Wildlife species description and significance

Great Plains Toad is endemic to the North American prairies. The species has been reassigned from the genus Bufo to a different genus, Anaxyrus. These toads are distinguishable from other species of toads in Canada by their relatively large size (47–115 mm snout-vent length [SVL] in adults), “L” -shaped cranial ridges behind the eyes, and dark paired blotches with light borders on a grey, light-brown, or olive-coloured back. Nocturnal and fossorial habits make the species difficult to document and monitor. The extremely loud call, described as a “harsh explosive clatter resembling a jackhammer”, is distinct from those of all other amphibians that co-occur in Canada. There is no species-specific Aboriginal Traditional Knowledge (ATK) in the report. All species are significant and are interconnected and interrelated.

Distribution

The distribution of Great Plains Toad extends from the southern parts of the Prairie Provinces in Canada (Manitoba, Saskatchewan, and Alberta) southwards through the North American grasslands to south-central Mexico. Within Canada, records are most numerous in Alberta, with additional scattered records across southern Saskatchewan and in the extreme southwestern corner of Manitoba.

Habitat

Great Plains Toad is associated with the grassland biome of North America. Adults are predominantly terrestrial and fossorial. Ephemeral pools are used as breeding habitat. Although it occurs in some cultivated areas, most records for the species in Canada are associated with native grassland.

Biology

Great Plains Toad spends most of its life underground. It emerges to breed and feed at night during the active season (April–September), especially in warm, humid conditions. It overwinters by burrowing below the frost line. Breeding occurs in spring in shallow temporary pools and is often stimulated by heavy rainfall. Individual toads may move more than 1 km during the active season. Generation time is approximately five years.

Population sizes and trends

Population sizes and trends are unknown. Great Plains Toad occurs in clusters at relatively low densities. Reproductive success varies highly from year to year and region to region. Under wet conditions, toads may reproduce in enormous numbers, but during drought years they may not breed at all. Numbers of adults fluctuate widely from year to year, reflecting this variation in precipitation during previous breeding seasons, although there are insufficient data to determine if fluctuations are “severe” (greater than an order of magnitude). In some parts of the species’ Canadian range, subpopulations have become scattered and isolated. Subpopulations are inferred to be declining across the entire range due to a decline in quality and quantity of habitat and the negative impacts of climate change.

Threats

Dams and water management are now the primary threat. Increased water management due to droughts, exacerbated by climate change, has resulted in increased irrigation, increased tile drainage, and less available water overall, all of which reduce available breeding habitat. Great Plains Toad was identified as highly vulnerable to climate change, particularly droughts, and storms and flooding. The secondary threat is annual and perennial non-timber crops.

Protection, status, and ranks

Prior to the current addendum, Great Plains Toad was designated (assessed) Special Concern in April 1999. The status was re-examined and confirmed in May 2002 and April 2010. This species was initially listed on Schedule 3 as Special Concern. In January 2005, the species was added to Schedule 1 with the status Special Concern. The species is ranked as N5 in USA, N3 in Canada, S2S3 in Alberta, S3 in Saskatchewan, and S2 in Manitoba. No special protection is afforded to the species in Alberta and Saskatchewan, although it is considered protected under the Endangered Species Act in Manitoba and protected under the Wildlife Act in Alberta.

Technical summary

Anaxyrus cognatus
Great Plains Toad
Crapaud des Grandes Plaines (previously Crapaud des steppes)
Range of occurrence in Canada (province/territory/ocean): Alberta, Saskatchewan, Manitoba

Demographic information

Explanation of changes since previous assessment

Quality of habitat

Quality of habitat is expected to continue to decline, leading to population declines, primarily because of two growing threats: changes in land management and climate change. The nature and impact of these threats are discussed below. Inferred decline in Box 2 and inferred reductions in Boxes 5–7 are based on the median value of population decline (range 10–70%) from the Assigned Overall Threat Impact of “High” from the Threats Calculator.

Survey information

Survey efforts have focused on detecting the species; no new information on abundance or population trends is available.

Extent and occupancy information

^* See COSEWIC Definitions and Abbreviations for more information on this term.

Explanation of changes since previous assessment

EOO: EOO from COSEWIC (2010) was 134,200 km². In this report, the EOO for records from 1957–2009 is 120,107 km². The recent EOO (2010–2019) is 154,922 km², an increase of 20,722 km² or 15.4% from the previous EOO (COSEWIC 2010). The recent EOO (2010–19) is an increase of 34,815 km² or 30.0% from the historical EOO (1957–2009) (Figure 1).

IAO: IAO from COSEWIC (2010) was 1,276 km². In this report, the IAO for records from 1957–2009 is 1,696 km². The recent IAO (2010–2019) is 1,708 km², an increase of 432 km² or 33.9% from the previous IAO (COSEWIC 2010). The recent IAO (2010–2019) is an increase of 12 km² or 0.07% from the historical IAO (1957–2009) (Figure 1).

Increases in known EOO and IAO likely reflect expanded search effort and not actual increases in occupancy, resulting in more complete knowledge of the species’ distribution, particularly in Saskatchewan and Manitoba.

Locations: The number of threat-based locations remains unknown but is above thresholds for assessment criteria (i.e., >10).

Survey information: In Alberta, there was little change in EOO or IAO from previous values (COSEWIC 2010). Most records were incidental, with one survey reported from 2018 northwest of Taber.

In Saskatchewan, there was an increase of records from Great Sandhills (western Saskatchewan). Surveys were conducted in 2010 in southwestern Saskatchewan (Fish and Wildlife Branch 2011). In addition, A. Didiuk conducted surveys in this region (larval surveys in 2010–2012, calling surveys in 2011–2012, and a time-limited survey in 2013–2014), but coordinates of occurrence records were not available for this report. Surveys were also conducted by A. Didiuk in southeastern Saskatchewan (near the Manitoba border) from 2013–2015, 2016, and 2018, as far west as Estevan, Saskatchewan (120 km west of the Saskatchewan-Manitoba border). In the surveys in western Saskatchewan, there were 816 wetlands and 1,260 roadside stops surveyed, with 130 detections. Great Plains Toad larvae were detected at 61 of the 861 wetlands (7.1%) and calling Great Plains Toad was detected at 69 of the 1,260 roadside stops (5.5%).

In Manitoba, there was increased survey effort from 2010 to 2019 (by Rutherford, Didiuk, and MB CDC) that resulted in more records in southwest Manitoba. This increased the IAO but did not change the overall range in Manitoba. In these surveys in southeastern Manitoba and within 30 km of the Saskatchewan border, there were 3,308 roadside stops surveyed. Calling Great Plains Toad was detected at 601 of the roadside stops (18.2%). In the surveys from 2013–2018, Great Plains Toad was detected within 30 km of the Saskatchewan-Manitoba border; these occurrences are continuous with those in southwestern Manitoba. These records were not available for this report but, if included, would generate a small increase in IAO, with no change in EOO.

Number of mature individuals (by subpopulation, indicating plausible ranges)

Explanation of changes since previous assessment

No changes since the last assessment.

Quantitative analysis

Is the probability of extinction in the wild at least 20% within 20 years or [5 generations, whichever is longer up to a maximum of 100 years], or 10% within 100 years?

Previous assessment: Unknown, analysis not conducted
Current assessment: Unknown, analysis not conducted

Explanation of changes since previous assessment

Unknown; analysis not conducted. Probability of extirpation in the wild is unknown.

Explanation of changes since previous assessment

There were few changes in identified threats, but threats were quantified in the recent Threats Calculator (December 2022). Dams and water management are now considered the primary threat. Increased water management due to droughts, exacerbated by climate change, has resulted in increased irrigation, increased tile drainage, and less available water overall, all of which reduce available breeding habitat. The impact of climate change, particularly droughts, was quantified by Shank and Nixon (2014). Great Plains Toad was identified as highly vulnerable to climate change.

Rescue effect (natural immigration from outside Canada)

⁺ See Table 3 (Guidelines for modifying status assessment based on rescue effect).

Explanation of changes since previous assessment

The Manitoba Conservation Status changed from S2S3 to S2 in 2010. There has been no change in the protection of the species. There has been a change in the PFRA program but no apparent intent by landowners to change land management practices, which suggests that there should not be further loss of habitat to cultivation. The Alberta Conservation Status changed from S2 to S2S3 in 2010.

IUCN Red List (Least Concern) (2015)

Global: G5 (2016)

United States: N5
Arizona: S5, Colorado: S4, Iowa: S4, Kansas: S5, Minnesota: S3, Missouri: S3, Montana: S2, Navajo Nation: S3, Nebraska: S5, Nevada: S2, New Mexico: S5, North Dakota: SNR, Oklahoma: SNR, South Dakota: S5, Texas: S5, Utah: S1, Wyoming: S3

Canada: N3
Alberta: S2S3, Saskatchewan: S3, Manitoba: S2

Likelihood of rescue from nearby US subpopulations remains low, because nearby subpopulations are also assessed as S2 (Montana) and S3 (Minnesota), although the North Dakota subpopulation is assessed as SNR.

Occurrence data sensitivity

Could release of certain occurrence data result in increased harm to the Wildlife Species or its habitat? No (current assessment)

Explanation of changes since previous assessment

Not applicable

Status history

COSEWIC Status History: Designated Special Concern in April 1999. Status re-examined and confirmed in May 2002 and April 2010. Status re-examined and confirmed in May 2023.

Status and reasons for designation

Status: Special concern

Alpha-numeric codes: Not applicable

Numeric code for change in status: Not applicable

Reasons for designation: This long-lived burrowing toad is patchily distributed across the southern Canadian prairie provinces. Spending most of its life underground, it emerges sporadically to feed and relies on small ephemeral water bodies to breed. Loss and degradation of habitat, particularly from changes in water management and agricultural land use, continue to impact this species. It is also vulnerable to increasing frequency and extent of drought linked to climate change. This reduces availability of already-restricted breeding sites both directly by lack of precipitation and indirectly by altering water management regimes, leading to recruitment failure and more pronounced population fluctuations.

Applicability of criteria

Criterion A: (Decline in Total number of Mature Individuals): Not applicable. Insufficient data to reliably infer, project, or suspect population trends, although “High” Overall Threat Impact from Threats Calculator projects a 10–70% decline over next three generations.

Criterion B: (Small Range and Decline or Fluctuation): Not applicable. IAO of 1,708 km² is below the threshold for Threatened, but population is not severely fragmented, and occurs at >10 locations.

Criterion C: (Small and Declining Number of Mature Individuals): Not applicable. Insufficient data to determine number of mature individuals, which likely exceeds 10,000, the threshold for Threatened.

Criterion D: (Very Small or Restricted Population): Not applicable. The population is neither very small nor restricted.

Criterion E: (Quantitative Analysis): Not applicable. No analysis conducted. (b) the Wildlife Species may become Threatened if factors suspected of negatively influencing the persistence of the Wildlife Species are neither reversed nor managed with demonstrable effectiveness.

Acknowledgements

Funding for the preparation of this report was provided by Environment and Climate Change Canada. The authorities listed below provided valuable data and/or advice. Thank you to Nicholas A. Cairns, Andrew Didiuk, Tom Herman, and Kristiina Ovaska (A&R SSC co-chairs). The previous report (COSEWIC 2010) was written by Janice James.

Authorities contacted

• Alberta Conservation Information Management System (ACIMS). September 2020. Edmonton, Alberta
• Benville, Andrea. September 2020. Saskatchewan Conservation Data Centre, Regina, Saskatchewan
• Bilyk, Lonnie. September 2020. Fish and Wildlife Management Information System (FWMIS), Environment and Parks, Government of Alberta, Edmonton, Alberta
• Buell, Daniel. September 2020. Land Administrator – Habitat, Wildlife & Access, Eastern Irrigation District (EID), Duchess, Alberta
• Collicutt, Doug. September 2020. Manitoba Herp Atlas, Winnipeg, Manitoba
• Didiuk, Andrew. September, October 2020, February 2021. Canadian Wildlife Service (now retired), Environment and Climate Change Canada, Saskatoon, Saskatchewan
• iNaturalist. September 2020. Data downloaded from Global Biodiversity and Information Facility, Free and open access to biodiversity data
• Murray, Colin. September 2020. Manitoba Conservation Data Centre, Winnipeg, Manitoba
• Poulin, Ray. September 2020. Manager, Research and Collections, Royal Saskatchewan Museum, Regina, Saskatchewan

Information sources

Alberta Environment and Parks. 2015. Great Plains Toad Conservation Management Plan 2015–2020. Alberta Environment and Parks. Species at Risk Conservation Management Plan No.11. Edmonton, Alberta. 8 pp.

Allred, B.W., W. Kolby Smith, D. Twidwell, J.H. Haggerty, S.W. Running, D.E. Naugle, and S.D. Fuhlendorf. 2015. Ecosystem services lost to oil and gas in North America. Science 348(6233):401–402.

COSEWIC. 2010. COSEWIC assessment and status report on the Great Plains Toad Anaxyrus cognatus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 54 pp.

Doke Sawatzky, K., and J.M. Piwowar. 2019. Changes in prairie grassland extent in Saskatchewan from 1990 to 2015. Prairie Perspectives: Geographical Essays 21:1–8.

Environment Canada. 2013. Management Plan for the Great Plains Toad (Anaxyrus cognatus) in Canada. Species at Risk Act Management Plan Series. Environment Canada, Ottawa. iii+ 16 pp.

Fish and Wildlife Branch. 2011. Predictive Habitat Modeling for Great Plains Toad (Anaxyurus Cognatus) in Southwestern Saskatchewan. Saskatchewan Environment, Saskatoon. 15 pp.

Hayhoe, K., and A. Stoner. 2019. Alberta’s Climate Future: Final Report 2019. Edmonton, AB: Environment and Parks, Edmonton. 50 pp.

Samson, F., and F. Knopf. 1994. Prairie conservation in North America. BioScience 44(6): 418–421.

Shank, C.C., and A. Nixon. 2014. Climate change vulnerability of Alberta’s biodiversity: A preliminary assessment. Alberta Biodiversity Monitoring Institute, Edmonton, Alberta.

World Wildlife Fund. 2021. The Plowprint Report: 2021 [PDF]. 4 pp.

Writer of addendum

Pamela Rutherford has expertise on prairie amphibians and reptiles, including Northern Prairie Skink (Plestiodon septentrionalis), Plains Hognose Snake (Heterodon nasicus), and Western Tiger Salamanders (Ambystoma mavortium). She has written numerous COSEWIC reports. She is an Associate Professor in the Department of Biology at Brandon University in Brandon, Manitoba, and is currently Co-Chair of the COSEWIC Amphibian & Reptile Specialist Sub-committee.

Appendix I: Threats calculator

Threats assessment worksheet

Species or ecosystem scientific name:

Great Plains Toad - Anaxyrus cognatus

Element ID:

Not applicable

Elcode:

Not applicable

Date:

2022-09-26

Assessor(s):

Pamela Rutherford (report writer), Tom Herman (Amphibians and Reptiles SSC Co-chair), Nick Cairns, Purnima Govindarajalu, Connie Browne, Andrew Didiuk, Thomas Hossie, Lea Randall, Praveen Jayarajan, Sandi Robertson, Robin Gutsell, Erin Swerdfeger, Katherine Yagi, Kris Kendell, Paulson Des Brisay, Bev McBride (Secretariat), Dave Fraser (facilitator)

References:

Environment Canada (2013), Alberta Environment and Parks (2015), Hayhoe and Stoner (2019)

Assigned overall threat impact:

B = High

Impact adjustment reasons:

Several scored threats were at the lower end of the range of values, which, cumulatively, should reduce the overall impact slightly.

Overall threat comments:

Not applicable

Classification of Threats adopted from IUCN-CMP, Salafsky et al. (2008).

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 (2023)

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)
(Note: Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.)

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)
(Note: Formerly described as “Not In Any Category”, or “No Designation Required.”)

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

Data deficient (DD)
(Note: 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.)

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.

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