Prairie Skink (Plestiodon septentrionalis): management plan 2025

Official title: Management Plan for the Prairie Skink (Plestiodon septentrionalis) in Canada 2025

Species at Risk Act
Management Plan Series

2025

Preface

The federal, provincial, and territorial government signatories under the Accord for the Protection of Species at Risk (1996)^{Footnote 2} agreed to establish complementary legislation and programs that provide for effective protection of species at risk throughout Canada. Under the Species at Risk Act (S.C. 2002, c.29) (SARA), the federal competent ministers are responsible for the preparation of management plans for listed species of special concern and are required to report on progress within five years after the publication of the final document on the SAR Public Registry.

The Minister of Environment and Climate Change Canada is the competent minister under SARA for the Prairie Skink and has prepared this management plan, as per section 65 of SARA. To the extent possible, the management plan has been prepared in cooperation with the Province of Manitoba and the .Department of National Defence as per section 66(1) of SARA.

Success in the conservation of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this plan and will not be achieved by Environment and Climate Change Canada or any other jurisdiction alone. All Canadians are invited to join in supporting and implementing this plan for the benefit of the Prairie Skink and Canadian society as a whole.

Implementation of this management plan is subject to appropriations, priorities, and budgetary constraints of the participating jurisdictions and organizations.

Acknowledgments

This document was prepared by Environment and Climate Change Canada, with input from representatives of federal and provincial governments, and regional experts. Environment and Climate Change Canada (ECCC) would like to thank the author Andrew Didiuk (ECCC) along with Medea Curteanu, Yeen Ten Hwang, Paulson Des Brisay and Emma Pascoe (ECCC) who reviewed, commented on and improved earlier versions of this document. The document benefited from reviews and comments received from Allison Krause Danielsen and Colin Murray (Manitoba Agriculture and Resource Development, Fish and Wildlife), Sherry Punak-Murphy (CFB Shilo, Manitoba) and Nicholas Cairns. The Manitoba Prairie Skink Recovery Team prepared a draft action plan (Manitoba Prairie Skink Recovery Team 2007) and a draft conservation and recovery strategy (Manitoba Prairie Skink Recovery Team 2014) which provided content for this management plan.

Executive summary

Prairie Skinks (Plestiodon septentrionalis) are small, slender burrowing terrestrial lizards (55 - 91 mm snout-vent length) with most adults less than 80 mm, and with olive-brown backs and sides and four light stripes running the length of the body and onto the tail. The tails of juvenile skinks are bright blue which fades to gray when they reach at least 50 mm snout-vent length. Males develop a reddish-orange patch on the chin during the breeding season.

The Prairie Skink has an extensive distribution throughout much of the great plains of North America from Manitoba to Texas. There are three subspecies with the Northern Prairie Skink occurring from southwest Manitoba to Kansas. The Northern Prairie Skink, hereafter referred to as the Prairie Skink, is found in the Brandon Sandhills area and the Lauder Sandhills area of southwest Manitoba, and the two areas are considered to be two separate populations. These are at the extreme northwest extent of their range in North America and they are approximately 130 km distant from the closest populations in northeast North Dakota. The extent of potential grassland habitat in southwest Manitoba for the Prairie Skink has been estimated to be approximately 73,638 hectares and it is associated with suitable sandy soils. The Prairie Skink was assessed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2004. Its status has been re-examined by COSEWIC in November 2017 and designated as Special Concern. This species was initially listed as Endangered on schedule 1 of the Species at Risk Act (SARA). This status was changed to Special Concern in April 2021. A management plan for Prairie Skink and its habitat has been prepared. The legal requirement of monitoring and reporting on the implementation of the “Recovery Strategy for the Prairie Skink (Plestiodon septentrionalis) in Canada” published on the Species at Risk Public Registry on March 2019, as stated in s.46 and s. 55 of SARA, is no longer applicable. The information that it contains could be used to manage the species and its habitat. All subsections of sections 58 and 61 and section 63 of SARA no longer apply to the critical habitat identified in the “Recovery Strategy for the Prairie Skink (Plestiodon septentrionalis) in Canada” .

There is no information available to assess trends of populations of the Prairie Skink. Threat assessment suggests there has been historical loss of habitat for the Prairie Skink (primarily through cultivation of grasslands) and historical and ongoing degradation of some habitat. There is likely some progressive decline in the amount and quality of habitat of the Prairie Skink but there is insufficient knowledge to measure the degree and trajectory of this decline, and the effects upon populations. The populations of the Prairie Skink do not appear to be significantly fragmented.

The Prairie Skink was listed as a Species of Special Concern because of past and ongoing threats to its habitat. The major threats to the species are IUCN-CMP Threat 8.1 Invasive non-native species, Threat 7.1 Fire and fire suppression (woody succession) and Threat 1.1 Housing and urban areas.

The objective of this management plan is to maintain the current distribution of the two Canadian populations (Brandon Sandhills and Lauder Sandhills) of the Prairie Skink, and any new populations which may be discovered in the future. The three broad strategies to achieve the management objective are habitat assessment, management, conservation and protection; monitoring, assessment and research; and communication, collaboration and engagement.

Conservation measures that are required to achieve the management objectives are outlined in this plan along with research required to address knowledge gaps. The development and adoption of best management practices, engagement of land owners and land managers, outreach and communication programs, population monitoring and research that address important knowledge gapswill be key management actions for this species.

1. COSEWIC* species assessment information

Date of assessment: November 2017

Common name (population): Prairie Skink

Scientific name: Plestiodon septentrionalis

COSEWIC status: Special Concern

Reason for designation: The Canadian distribution of this species is restricted to a small area of mixed-grass prairie on sandy soils in Manitoba and is isolated from the rest of the species’ range in the USA by over 100 km. Its prairie habitat has been historically lost and fragmented mainly due to agricultural activities. Aspen succession and invasion by exotic plants continue to degrade remaining habitats. Several new localities have been discovered within the known range since the last assessment as a result of increased survey efforts, and habitat management is ongoing within portions of the skink’s range on federal and provincial lands. Change in status from the previous assessment results from a different interpretation of status assessment criteria by COSEWIC. While the species is deemed to no longer be at risk of imminent extinction, it could become Threatened if factors affecting it are unmitigated.

Canadian occurrence: Manitoba

COSEWIC status history: Designated Special Concern in April 1989. Status re examined and designated Endangered in May 2004. Status reexamined and designated Special Concern in November 2017.

* COSEWIC (Committee on the Status of Endangered Wildlife in Canada)

2. Species status information

Status ranks for the Prairie Skink (Plestiodon septentrionalis) are listed inTable 1. The International Union for Conservation of Nature (IUCN) has designated the species as “least concern” (IUCN 2020) based on an assessment in 2007, which requires updating. COSEWIC assessed the Prairie Skink as Endangered in 2004 and it was added to Schedule 1 of the Canadian Species at Risk Act (SARA). In 2017, COSEWIC re‑assessed Prairie Skink as Special Concern, and on April 23, 2021 it was added to Schedule 1 of SARA as this new status designation.

Approximately <5% of the species’ distribution is within Canada. The Prairie Skink was listed as Endangered in Manitoba under the Endangered Species and Ecosystems Act in 2012 (Manitoba Wildlife Branch 2016).

^a The NatureServe conservation status of a species is designated by a letter reflecting the appropriate geographic scale of the assessment (G = Global, N = National, and S = Subnational) followed by a number from 1 to 5 or other letters. The numbers and letters have the following meaning: 1 = critically imperiled, 2 = imperiled, 3 = vulnerable, 4 = apparently secure, and 5 = secure. Letters indicate: NR = not ranked.

3. Species information

3.1. Species description

Prairie Skinks are small, slender burrowing terrestrial lizards (55 - 91 mm snout-vent length) with most adults less than 80 mm, and with olive-brown backs and sides and four light stripes running the length of the body and onto the tail The tail is approximately the same length as the body, but may be shorter if the tail has previously been lost and regenerated. Tails of juvenile skinks are bright blue which fades to gray when they reach at least 50 mm snout-vent length (Breckenridge 1943). Males develop a reddish-orange patch on the chin during the breeding season (COSEWIC 2004).

3.2. Species population and distribution

3.2.1 Species distribution

The Prairie Skink has an extensive distribution throughout much of the Great Plains of North America, from Manitoba to Texas (Figure 1). The species is divided into three subspecies (Crowther 2012): the Northern Prairie Skink (P. s. septentrionalis) which extends from southwest Manitoba to Kansas, the Southern Prairie Skink (P. s. obtusirostris)), and the Pallid Skink (P. s. pallidus)) which occurs in Oklahoma, Texas, Arkansas and Louisiana.

Prairie Skink populations in southwest Manitoba are at the extreme northwest extent of their range in North America, and are approximately 130 km from the closest populations in extreme northeast North Dakota.

Figure 1. North American distribution of the Northern Prairie Skink (dark shading) and the Southern and Pallid Prairie Skinks (light shading) (from COSEWIC 2004).

Prairie Skinks addressed in this management plan are those found in the Brandon Sandhills area and the Lauder Sandhills area (Figure 2), and are considered to be two separate populations.

The amount and spatial distribution of potential habitat for the Prairie Skink is of importance in a management plan. It confirms the extent of distribution of populations and occupied habitat, it targets conservation measures, and it provides a framework for monitoring. The potential habitat extent is necessary for assessing abundance and the relationship of abundance and habitat characteristics. This importance warrants an overview of the various efforts to estimate area extent of Prairie Skink habitat.

Figure 2. The Canadian range of the Prairie Skink with two disjunct populations in southwest Manitoba, the Brandon Sandhills area and the Lauder Sandhills area (from Environment and Climate Change Canada 2016).

Calculations of the extent of occurrence (EO)^{Footnote 3} and index of area of occupancy (IAO)^{Footnote 4} allows COSEWIC a means of estimating general range for all species in a consistent manner. However, this approach usually results in an over estimate of range extent through inclusion of unsuitable habitat, and an under estimate of actual extent of populations as only occurrences detected at the time of assessment are utilized. Of the efforts used to identify all currently known Canadian populations (Table 2) only the most recent provides a measure of habitat based upon both presence of grassland and underlying suitable sandy soils necessary for winter survival. The most recent assessment of the extent of potential habitat of the Prairie Skink (Didiuk and Harder 2022) may provide a more meaningful estimate of extent of potential habitat. This assessment created a map of potential grassland habitat for the Prairie Skink (Figure 3) from integration of the extent of sandy soil textures and grassland land cover from classification of high-resolution satellite imagery.

^a Bredin 1989) estimates of area of suitable soils - 140,000 hectares of Minotoa Loamy Sand Association plus 37,000 hectares of Miniota Sand Association, not 3,700 hectares which is error in Habitat Section 2^nd paragraph pg. 8.

Figure 3. Extent of grassland (yellow) and woodland (green) habitat with suitable soils, and locations of records of the Prairie Skink (black dots; Didiuk and Harder 2022).

The extent of potential grassland habitat in southwest Manitoba for the Prairie Skink was estimated to be 73,638 hectares within 11 regions of interest. Six regions (54,288 hectares of potential grassland habitat) encompassed all confirmed occurrences of the Prairie Skink as of 2015. Five regions (19,350 hectares of potential grassland habitat) require surveys of sufficient effort to confirm presence of populations of the Prairie Skink. However, these latter regions are not very distant from existing populations and have the same suitable sandy soil underlying grassland. The historical record south of Gladstone has not been recently assessed. Its location beyond the Manitoba Escarpment in an area with silt-dominated soils suggests low likelihood of the occurrence of Prairie Skinks, but the site and areas of grassland habitat nearby should be investigated.

The grassland map has high accuracy due to the limited number of classes (grassland, woodland, exposed substrate and water) and detailed manual editing to exclude potential misclassification areas (e.g. hayland, wetland, communities, transportation corridor surfaces). However, the grassland map does not distinguish among areas which may provide optimal habitat conditions and possibly high relative abundance of the Prairie Skink, versus less optimal conditions and low relative abundance. This grassland map may therefore be considered as representing the likely maximum extent of habitat for the Prairie Skink, and can serve as a framework for future evaluation of presence and relative abundance of the Prairie Skink.

The Brandon Sandhills area is within the Shilo Ecodistrict of the post-glacial Upper Assiniboine Delta deposits (Wolfe 2010). It extends from near Neepawa in the north to near Glenboro in the south, and from the western border of Canadian Force Base (CFB) Shilo in the west to approximately 12 km north of Treherne in the east. There are fewer confirmed occurrences in the northern end of the central lobe of projected distribution, towards Neepawa, and in the eastern end of the lobe extending northeast of Treherne, likely representing limited survey effort (Figure 2).

The Lauder Sandhills area is within the Oak Lake Ecodistrict of the Souris Till Plain. This Prarie Skink population was reported to have an occupied area less than 1 ha in extent (Manitoba Prairie Skink Recovery Team 2014 within the Lauder Sandhills Wildlife Management Area, but a cover board survey in 2015 (Didiuk et al. 2015), and some additional checks of these cover boards in 2016 resulted in the detection of additional occurrences in this area. The Prairie Skink may be distributed widely throughout much of the Lauder Sandhills and adjacent sandhill areas.

Although some surveys have been conducted north of the Lauder Sandhills, in the Routledge, Oak Lake and Souris Sandhills, there have been no detections of the Prairie Skink (COSEWIC 2017; C. Murray, pers. comm.).

Prairie Skinks in the Lauder Sandhills area are 80 km from the Brandon Sandhills area to the east. The eastern edge of the Brandon Sandhills populations are isolated from the nearest Prairie Skink populations in extreme northeast North Dakota by approximately 130 km. There has been no survey effort to detect Prairie Skinks in the small areas of sandy soils near Alexander, between the Lauder Sandhills and the Brandon Sandhills.

3.2.2 Population abundance and trends

The cryptic nature of the Prairie Skink, and the low recapture rates of marked individuals typical of many reptile species, make assessment of abundance very difficult.

Bredin (1989) calculated a density of 48.75 skinks/ha from captures and recaptures of 108 marked skinks at a 16 ha study area at CFB Shilo from 1981 to 1983. However, the approach for deriving this estimate was not provided. No searches were conducted in areas of purely natural cover where it is extremely difficult to find individuals and it is likely this density estimate is not applicable to populations using natural habitat.

Rutherford (2015, and 2013 unpublished) estimated population density for five sites (including the study area of Bredin (1989) at CFB Shilo in 2007 to 2011, using a closed capture model.^{Footnote 5} Estimated density at four of the five sites ranged from 1.3 to 2.8 skinks/ha. The very low density estimates of Rutherford (2015, and 2013 unpublished) of less than 2-3 skinks/ha are unexpected given other much higher estimates of density for the Prairie Skink and other species of skinks with similar ecological attributes.

A large grid sampling effort was conducted in 2016 at a 22.1 ha site at CFB Shilo and at a 28.3 ha site at Spruce Woods Provincial Park (SWPP; Didiuk, 2017 unpubl. data). The density in grassland (grass and grass/open shrub cover types) was estimated to be 339 skinks/ha at the SWPP site and 97 skinks/ha at the CFB Shilo site. The density in open woodland was estimated to be 99 skinks/ha at the SWPP site and 90 skinks/ha at the Shilo site.

Additional sampling of Prairie Skink populations is necessary to evaluate the variation of density of local populations (multiple areas of occupancy in habitat patches throughout its range) with variable habitat characteristics. At that time, it may be possible to estimate the total population size of the Prairie Skink in Manitoba.

There is no information available to assess trends of populations of the Prairie Skink.

A population density estimate for one study site was lower in 2011 (P. Rutherford, unpubl. data 2013) than in 1989 (Bredin 1989) but these estimates were calculated using different techniques. Persistence of element occurrences from the Manitoba Conservation Data Centre are difficult to interpret as there has been an increasing survey effort over the years (COSEWIC 2017). Also, if insufficient survey effort is applied to given locations it is problematical to consider populations to be extirpated as presence of Prairie Skinks was reconfirmed at or very near three locations (ECCC, 2020) where populations were considered to be extirpated (COSEWIC 2017).

Population abundance of the Prairie Skink can likely vary considerably among years, presumably a reflection of climatic factors and their effect upon recruitment. Densities of the Five-lined Skinks in Kansas varied considerably among years (Fitch 1954).

Results of the threats calculator assessment (Table 3) suggest there has been historical loss of habitat for the Prairie Skink through cultivation of grasslands and historical and ongoing degradation of some habitat from invasive species (notably Leafy Spurge Euphorbia virgata^{Footnote 6}) and woody succession. Rutherford et al. (2012) estimated 19% loss of habitat for Prairie Skinks from agricultural activities outside of CFB Shilo and Spruce Woods Provincial Park. This was calculated by examining lands with suitable sandy soils and land use data from 1966-2000. However, in the Brandon Sandhills area there was a 26% increase in grassland primarily from landowners clearing woodland for grazing (Rutherford, unpublished data).

The effect of livestock grazing upon grassland habitat of the Prairie Skink, which is pervasive outside of CFB Shilo and SWPP, is currently unknown. There is likely some progressive decline in the amount and quality of habitat of the Prairie Skink, but there is insufficient knowledge to measure the degree and trajectory of this decline. Local populations of the Prairie Skink within the Brandon and Lauder Sandhill areas do not appear to be significantly fragmented, with extensive connectivity of grassland habitat underlain by sandy soils (COSEWIC 2017).

3.3. Needs of the Prairie Skink

3.3.1. Biological needs

Prairie Skinks are associated with mixed-grass prairie and savannah habitats

(Breckenridge 1943; Bredin 1989; COSEWIC 2017) with soil texture generally having a 75-85% sand content (Cairns 2007). This habitat in Manitoba and elsewhere is usually associated with sandhill topography where slope and sandy soils limit potential for cultivation.

Prairie Skinks feed on a variety of small invertebrates, including crickets, grasshoppers, spiders and moth larvae (COSEWIC 2017).

The Prairie Skink is an ectotherm and uses a variety of behavioural mechanisms to optimize body temperature and avoid predation. Prairie Skinks will bask to achieve a optimal body temperature to become active (e.g. foraging, mate searching nest site searching) and will seek shade or retreats to avoid lethal higher body temperatures. They employ shuttling behaviour, in and out of shade, to remain active during periods of high temperature arising from solar insolation. The structure of vegetation and of surface cover objects provide retreats and partial or full shading to accommodate movements. Movements, and use of given vegetation and surface objects, represent a balance among thermal conditions, need to move (eg. foraging or mate seeking) and avoidance of predation. The Prairie Skink appears to be highly sedentary (Nelson 1963; Bredin 1989; Rutherford 2013, 2015)

Open grassland, with limited shrub canopy, provides suitable habitat for the Prairie Skink (Breckenridge 1943; Nelson 1963; Bredin 1989; Scott 2005; Krause Daniels et al. 2014). There appears to be some limited use of open canopy tree cover, particularly along the immediate edges of woodland (Rutherford, unpubl. data 2013; Didiuk, unpubl. data 2021).

Prairie Skinks emerge from wintering site from late April to early May. Most skinks are inactive and presumably at or near wintering sites by mid September. Mating occurs from mid May to mid June, with males developing an orange colouration on the chin area. Females excavate shallow burrows in late June to early July and lay clutches of 1 to 12 or more eggs (Somma 1987; Bredin 1988; Rutherford 2015). The females attend their clutches and eggs hatch in the last week of July and the first week of August (Breckenridge 1943; Nelson 1963; Bredin 1988, 1989).

It is presumed that Prairie Skinks burrow in sandy soil to below the frost line to avoid winter freezing conditions. There is no information regarding wintering sites of the Prairie Skink in Manitoba.

3.3.2. Limiting factors

It is important to distinguish between limiting factors and threats. Limiting factors are generally not human induced and include characteristics that make the species or ecosystem less likely to respond to recovery/conservation efforts (e.g., inbreeding depression, small population size, and genetic isolation, or likelihood of regeneration or recolonization for ecosystems). Limiting factors are not considered during this assessment process.

The Prairie Skink in southwest Manitoba is at the extreme northwestern edge of its global range. The Canadian distribution is restricted to areas of mixed-grass prairie on sandy soils. Mortality of the Prairie Skink may be greater during winters with limited snow cover which allows greater depth of frost penetration in the soil, particularly for hatchlings during their first winter period (Bredin 1989). Prolonged cold and wet weather during the summer active period can reduce recruitment through reduced reproductive activity or lower hatching success of eggs. The inclement weather can also reduce the ability of adults and young to forage and store fat reserves for the following winter (Derickson 1976).

4. Threats

4.1. Threat assessment

The Prairie Skink threat assessment is based on the IUCN-CMP (World Conservation Union – Conservation Measures Partnership) unified threats classification system. Threats are defined as the proximate activities or processes that have caused, are causing, or may cause in the future the destruction, degradation, and/or impairment of the entity being assessed (population, species, community, or ecosystem) in the area of interest (global, national, or subnational). Limiting factors are not considered during this assessment process. For purposes of threat assessment, only present and future threats are considered. Historical threats, indirect or cumulative effects of the threats, or any other relevant information that would help understand the nature of the threats are presented in the Description of Threats section.

^a Impact – The degree to which a species is observed, inferred, or suspected to be directly or indirectly threatened in the area of interest. The impact of each threat is based on Severity and Scope rating and considers only present and future threats. Threat impact reflects a reduction of a species population or decline/degradation of the area of an ecosystem. The median rate of population reduction or area decline for each combination of scope and severity corresponds to the following classes of threat impact: Very High (75% declines), High (40%), Medium (15%), and Low (3%). Unknown: used when impact cannot be determined (e.g., if values for either scope or severity are unknown); Not Calculated: impact not calculated as threat is outside the assessment timeframe (e.g., timing is insignificant/negligible or low as threat is only considered to be in the past); Negligible: when scope or severity is negligible; Not a Threat: when severity is scored as neutral or potential benefit.

^b Scope – Proportion of the species that can reasonably be expected to be affected by the threat within 10 years. Usually measured as a proportion of the species’ population in the area of interest. (Pervasive = 71–100%; Large = 31–70%; Restricted = 11–30%; Small = 1–10%; Negligible < 1%).

^c Severity – Within the scope, the level of damage to the species from the threat that can reasonably be expected to be affected by the threat within a 10-year or three-generation timeframe. Usually measured as the degree of reduction of the species’ population. (Extreme = 71–100%; Serious = 31–70%; Moderate = 11–30%; Slight = 1–10%; Negligible < 1%; Neutral or Potential Benefit ≥ 0%).

^d Timing – High = continuing; Moderate = only in the future (could happen in the short term [< 10 years or 3 generations]) or now suspended (could come back in the short term); Low = only in the future (could happen in the long term) or now suspended (could come back in the long term); Insignificant/Negligible = only in the past and unlikely to return, or no direct effect but limiting.

4.2. Description of threats

The overall threat impact for this species is Medium to Low (threat calculator COSEWIC 2017) and considers the cumulative impacts of all threats identified (IUCN-CMP 2006).

This overall threat impact was based on one medium – low threat impact (Invasive and other problematic species and genes) and two low threat impacts (Natural System Modifications and Residential and Commercial Development). Three threat impacts were considered to be unknown (Agriculture and Aquaculture, Pollution, Climate Change and Severe Weather), and three threat impacts were considered to be negligible (Transportation and services corridors, Biological resource use, Human intrusions and disturbance,). Details are discussed below for threats that are identified as Low impact or greater in their perceived order of importance.

IUCN-CMP threat 8. Invasive and other problematic species and genes

Threat 8.1 invasive non-native/alien species (medium-low)

The invasive plants Leafy Spurge (Euphorbia virgata) and Smooth Brome (Bromus inermis), both of European origin, are threats to the native mixed-grass prairie habitat due to their aggressive replacement of native vegetation. There are significant knowledge gaps on the effects of Leafy Spurge and Smooth Brome on skinks.

Leafy Spurge plants can grow up to one metre in height, reproduce vegetatively or by seed and are readily introduced by anthropogenic disturbances such as vehicle tracks (Belcher and Wilson 1989). In Manitoba it is widely established and currently occurs in approximately 52,600 ha (Province of Manitoba 2015a). Efforts to eradicate Leafy Spurge have been undertaken in Canada and the US but the species continues to be a problem (Team Leafy Spurge 2005; Province of Manitoba 2015a).

Leafy Spurge was considered to be a potential threat to the Prairie Skink (Bredin 1989) due to possible reduced thermal suitability of sites from shading and replacement of native vegetation. It can be found on every Prairie Skink site examined (Rutherford, pers. comm. 2017). Dense stands of Leafy Spurge reduce structural heterogeneity of the habitat and could limit thermoregulatory options (COSEWIC 2017). Prairie Skinks have appeared to have abandoned sites following colonization by this invasive plant (Bredin 1988).

However, the actual effect on Prairie Skinks is unclear. Larkin (2011) demonstrated that ground surface thermal conditions in stands of Leafy Spurge were not significantly different from those in adjacent prairie habitat. Rutherford (2010) found Prairie Skink abundance in Leafy Spurge and control patches to be comparable. Didiuk (2017, unpubl. data) detected Prairie Skinks in many patches of Leafy Spurge of varying density, but with no apparent presence detected in stands with coverage >70%. The impact of Smooth Brome to the prairie is uncertain, but its high abundance could have negative effects similar to those postulated for Leafy Spurge (COSEWIC 2017).

Leafy Spurge has been managed using chemical control, cultivation, planting competitive crop species, mowing, burning, tilling, grazing by domestic sheep (Ovis aries) and goats (Capra aegagrushircus), and biological control (COSEWIC 2017). Chemicals have been used for control of Leafy Spurge in Spruce Woods Provincial Park (Manitoba Conservation and Water Stewardship 2012). Goats have been effective at reducing Leafy Spurge but many years of grazing are needed for effective control (Manitoba Conservation and Water Stewardship 2012; Province of Manitoba 2015b). Chemical control, cultivation, planting competitive crop species, and tilling are unsuitable controls modes in Prairie Skink habitat. The potential effects of mowing, burning, and grazing upon Prairie Skinks and their habitat is not known.

The use of flea beetles (Aphthona sp.) has been most effective (Province of Manitoba 2015a). Although it takes time for populations to become established, flea beetles have removed 95% of the Leafy Spurge at some of the earliest release sites (Province of Manitoba 2015a).

Smooth Brome generally occurs in relatively isolated patches but it continues to expand its occurrence in skink habitats, and the patches of this species can have a relatively large basal area when compared to Leafy Spurge (COSEWIC 2017). Skinks appear to continue using habitat with patches of Smooth Brome patches but such patches may need to be interspersed with native prairie to provide adequate habitat (Rutherford pers. comm. 2016).

Additionally, half of landowners in areas with Prairie Skink occurrences who own freeranging. domestic cats reported seeing evidence of cats killing skinks (Krause Danielsen 2012). The population-level effects of this predation by a non-native species is unknown.

This threat was assessed as pervasive in scope (71–100% of the population affected) and moderate-slight in severity (1–30% decline expected at affected sites). A range was used for severity because of significant knowledge gaps on whether, or under what conditions, skinks can co-occur with Leafy Spurge and other invasive plants.

IUCN-CMP threat 7. Natural ecosystem modifications

Threat 7.1 fire and fire suppression (low)

Prairie Skinks require the open yet heterogeneous vegetation structure of native mixed‑grass prairie. Fire suppression throughout southwest Manitoba is considered to be a threat to mixed-grass prairie habitat as woody succession increases vegetation height and density, and increases shade from low and high canopies of shrubs and trees. This process of increased shade reduces thermal suitability of habitat. Bredin (unpubl. data 2003, in COSEWIC 2004) considered woody succession to have caused the disappearance of Prairie Skinks from at least four areas.

The effect of increased litter (layer of dead plant material) from fire suppression on Prairie Skink habitat is not clear. Increased insulation could reduce the active season for Prairie Skinks whereas regular burning reduces litter and can result in higher soils surface temperatures during the growing season (Shay et al. 2001). Prairie Skinks were more abundant in old fields that were burned regularly in Minnesota than in habitats that were not burned (Pitt 2001), whereas Prairie Skinks selected habitat with a higher percentage of leaf litter in Manitoba (Krause Danielsen et al. (2014). The environmental context of a site may dictate whether the effects of litter accumulation or reduction are positive or negative (COSEWIC 2017).

The grazing of cattle may slow down woody succession but is not sufficient to prevent it (Oliver 2008). Mechanical mowing to suppress woody vegetation can allow Prairie Skink populations to persist in the short-term without fire (Fitch, 2006), but it would likely not be feasible at the scale required for management of this species in Canada. Future climate change could possibly slow down the rate of succession as higher temperatures and increase in drought conditions are predicted for Manitoba (Lemmen and Warren 2004). These changes could reduce the survival and establishment woody vegetation (Chhin and Wang 2002; Hogg et al. 2002; Chhin et al. 2004).

This threat was assessed as large in scope (31–70% of population affected) because woody succession is a concern throughout much of the skinks’ range, and slight in severity (1–10% decline expected at affected sites).

IUCN-CMP threat 1. Residential and commercial development

1.1 Housing and urban areas (low)

Residential development affects Prairie Skinks though vegetation and soil disturbance, often by conversion of native prairie into gardens and Kentucky Bluegrass (Poa pratensis) lawns resulting in loss and fragmentation of habitat. Multiple issues for the Prairie Skink occur in residential landscapes, including mowing lawns, predation by pets, and traffic (Krause Danielsen et al. 2014). Some residential development is occurring adjacent to SWPP and CFB Shilo but is of limited extent throughout the range of the Prairie Skink.

This threat was assessed as small in scope (1–10% of the population affected), and possibly the scope could be near negligible. The severity was assessed as slight (1–10% decline expected at affected sites).

5. Management objective

The management objective for the Prairie Skink is to maintain the current distribution of all local populations within the Brandon Sandhills and the Lauder Sandhills and any new local populations which may be discovered in the future.

Occurrence of the Prairie Skink has been confirmed for only a very small proportion of apparently suitable habitat in southwest Manitoba. Estimates of population size are unlikely to be obtained without extremely high survey effort due to the low detectability of skinks arising from their small size, cryptic behaviour and possible low density in some occupied habitats. Therefore, it is not feasible at this time to set quantitative population objectives. It is recognized that the management objective and broad strategies may take considerable time for de-listing the species.

6. Broad strategies and conservation measures

6.1. Actions already completed or currently underway

Habitat assessment, management, conservation and protection

Habitat assessment

• Habitat suitability based on suitable sandy soils have been identified and mapped (Bredin 1989, 1993)
• Manitoba Conservation Data Centre staff have identified potential habitat of the Prairie Skink at several locations in Manitoba during plant species at risk inventories (Reimer and Hamel 2002; Hamel and Foster 2005; Foster and Hamel 2006; Murray and Friesen 2012), and such surveys continue
• Extent of habitat of the Prairie Skink was assessed by mapping of suitable soils (Bredin 1989) and suitable soils and temperature (Cairns 2017)
• Estimates in change of the extent of grassland habitat of the Prairie Skink was assessed by mapping suitable soils and land use (Rutherford et al. 2012)
• Extent of grassland habitat of the Prairie Skink was mapped by integrating extent of suitable sandy soils and extent of grassland cover derived from classification of satellite imagery (Didiuk and Harder 2022)

Habitat management

• Prescribed burns are conducted within Spruce Woods Provincial Park at sites designated by the Prairie Management Plan (Schykulski and Moore 2000), at CFB Shilo, and at various sites managed by Nature Conservancy of Canada
• Nature Conservancy of Canada applies a Multi-Species at Risk Management and Recovery planning framework to perform active management of lands that it manages, and targets the Prairie Skink
• Chemicals have been used for control of Leafy Spurge in Spruce Woods Provincial Park (Manitoba Conservation and Water Stewardship 2012)
• Flea beetle populations for control of Leafy Spurge have been established at CFB Shilo and Spruce Woods Provincial Park

Conservation and protection

• Nature Conservancy of Canada has secured sandhill habitat in the Lauder Sandhills area, which provide protection of grassland habitat for the Prairie Skink
• A variety of conservation lands provide protection and conservation measures of habitat suitable for the Prairie Skink, and some known populations (see Didiuk and Harder 2002. for evaluation of grassland habitat protection)

Monitoring, assessment and research

Assessment

• All occurrences of the Prairie Skink, historical and new, are reported to and archived at the Manitoba Conservation Data Centre
• University of Brandon academic research programs (Dr. Pam Rutherford and graduate students) and Canadian Wildlife Service research programs (Andrew Didiuk) have identified sites of occurrence of the Prairie Skink

Monitoring

• CFB Shilo and Nature Conservancy of Canada monitor the persistence of local populations of the Prairie Skink

Research

• Research has been undertaken to improve understanding of microhabitat selection by Prairie Skinks within native mixed-grass prairie and rural residential developments (Scott 2005; Larkin 2011; Krause Danielsen et al. 2014; Rutherford, unpubl. data; Didiuk, unpubl. data)
• Research has been undertaken to improve understanding of demographics of the Prairie Skink (Bredin 1988, 1989; Rutherford, unpubl. data; Didiuk, unpubl. data)
• Research has been undertaken to improve understanding of the movements of the Prairie Skink (Rutherford, unpubl data; Didiuk, unpubl. data)
• Research has been undertaken to improve understanding of the density of Prairie Skink populations (Rutherford 2015; Didiuk et al. 2021c)

Communication, collaboration and engagement

• Community outreach occurs through a ‘Save our Skink’ website
• Annual Skinkfest celebrations occur at Spruce Woods Provincial Park
• Save Our Skinks
• Community outreach with land managers has been conducted
• Briefings on Species at Risk, which includes Prarie Skink, are given at CFB Shilo

6.2 Broad strategies

To achieve the objectives of this management plan, three broad strategies are recommended:

1. Habitat assessment, management, conservation and protection. Assess threats to habitat at sites occupied by the Prairie Skink, prioritize sites for protection and management of habitat, identify approaches for best management practices, and engage landowners and land manages for implementation of best management practices
2. Assessment, monitoring and research. Conduct surveys to determine the locations of Prairie Skink populations, develop and implement a monitoring program to track population, though density estimates, relative abundance, or site occupancy, and habitat quality, address knowledge gaps including evaluating the impacts of invasive plants, fire suppression and grazing; determining microhabitat requirements to guide development of best management practices; and determine demographic parameters and vital rates
3. Communication, collaboration and engagement. Continue to monitor populations to assess changes in population abundance and distribution. This could be accomplished, in part, though engaging and encouraging landowners, resources users, and recreationists to submit obeservations to community science projects such as iNaturalist.

6.3 Conservation measures

^a “Priority” reflects the degree to which the measure contributes directly to the conservation of the species or is an essential precursor to a measure that contributes to the conservation of the species. High priority measures are considered those most likely to have an immediate and/or direct influence on attaining the management objective for the species. Medium priority measures may have a less immediate or less direct influence on reaching the management objective, but are still important for the management of the population. Low priority conservation measures will likely have an indirect or gradual influence on reaching the management objective, but are considered important contributions to the knowledge base and/or public involvement and acceptance of the species.

6.4 Narrative to support conservation measures and implementation schedule

Although much of the remaining potential grassland habitat for the Prairie Skink is located in rolling sandhill terrain, where slope and sandy soils limit losses to cultivation, conservation activities are required to prevent any further losses of grassland habitat. Degradation of habitat quality arising from invasive plants, and fire suppression which promotes woody success in grassland habitat, are concerns that require prompt assessment and increased management actions. Conservation and restoration of grassland habitat may be realized through a variety of programs, including stewardship and land management agreements, conservation easements, and land purchase. Extensive programs including extension education, policy reforms, and tax incentives, may also assist in conserving and maintaining grassland habitat of good quality for the Prairie Skink.

Strategic surveys are necessary to detect locations of Prairie Skink populations throughout its potential grassland range. These surveys can use existing grassland habitat maps and apply a survey protocol that ensures sufficient survey effort to provide a reasonable probability of detection. Evaluation of landscape and micro-habitat features during these surveys can enhance understanding of habitat requirements for best management practices. Research programs to address key knowledge gaps, in particular the effects of invasive plants, fire suppression and livestock grazing, are necessary to guide habitat protection measures and the approaches for monitoring populations of the Prairie Skink and its grassland habitat.

Communication efforts are ongoing, and are important tools for the implementation of habitat management and protection by landowner and land manager engagement. Community outreach with landowners, and through the ‘Save our Skink’ website and the annual Skinkfest celebrations at Spruce Woods Provincial Park, should continue.

7. Measuring progress

The performance indicators presented below provide a way to measure progress towards achieving the management objectives and monitoring the implementation of the management plan.

• Persistence of known local populations of the Prairie Skink is monitored and confirmed within the Brandon Sandhills area and the Lauder Sandhills area plus any new local populations discovered in the future
• Population and habitat monitoring trends indicate stable or increasing populations and habitat extent and quality

8. References

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Appendix A: Effects on the environment and other species

A strategic environmental assessment (SEA) is conducted on all SARA recovery planning documents, in accordance with The Cabinet Directive on the Environmental Assessment of Policy, Plan and Program Proposals ^{Footnote 7}. The purpose of a SEA is to incorporate environmental considerations into the development of public policies, plans, and program proposals to support environmentally sound decision-making and to evaluate whether the outcomes of a recovery planning document could affect any component of the environment or any of the Federal Sustainable Development Strategy’s (FSDS)^{Footnote 8} goals and targets.

Conservation planning is intended to benefit species at risk and biodiversity in general. However, it is recognized that implementation of management plans may also inadvertently lead to environmental effects beyond the intended benefits. The planning process based on national guidelines directly incorporates consideration of all environmental effects, with a particular focus on possible impacts upon non-target species or habitats. The results of the SEA are incorporated directly into the management plan itself, but are also summarized below in this statement.

Conservation of mixed-grass prairie underlain by sandy soils, the primary aspect of this management plan, does not negatively impact other wildlife. Protections and management of grassland habitat of the Prairie Skink will positively benefit rare plants including federally listed species, such as Hairy Prairie-clover (Dalea villosa), Western Spiderwort (Tradescantia occidentalis) and Smooth Goosefoot (Chenopodium subglabrum), as well as some listed bird species, such as Sprague’s Pipit (Anthus spragueii).

The development and promotion of agricultural best management practices, will be beneficial not only to the Prairie Skink but to other species that use similar habitat.