COSEWIC Assessment and Status Report on the Prairie Skink Plestiodon septentrionalis in Canada SPECIAL CONCERN 2017 COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows: COSEWIC. 2017. COSEWIC assessment and status report on the Prairie Skink Plestiodon septentrionalis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xiii + 48 pp. (http://www.registrelep-sararegistry.gc.ca/default.asp?lang=en&n=24F7211B-1). Previous report(s): COSEWIC 2004. COSEWIC assessment and update status report on the prairie skink Eumeces septentrionalis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 22 pp. (www.sararegistry.gc.ca/status/status_e.cfm). Bredin, E.J. 1989. COSEWIC status report on northern prairie skink Eumeces septentrionalis septentrionalis in Canada. Committee on the Status of Endangered Wildlife in Canada. 41 pp. Production note: COSEWIC would like to acknowledge Connie Browne for writing a draft of the status report on Prairie Skink (Plestiodon septentrionalis) in Canada, prepared under contract with Environment Canada and Climate Change. This report was overseen by Kristiina Ovaska, Co-chair of the COSEWIC Amphibians and Reptiles Specialist Subcommittee. For additional copies contact: COSEWIC Secretariat c/o Canadian Wildlife Service Environment and Climate Change Canada Ottawa, ON K1A 0H3 Tel.: 819-938-4125 Fax: 819-938-3984 E-mail: [email protected] http://www.cosewic.gc.ca Également disponible en français sous le titre Ếvaluation et Rapport de situation du COSEPAC sur le Scinque des prairies (Plestiodon septentrionalis) au Canada. Cover illustration/photo: Prairie Skink — photo by Errol Bredin. Her Majesty the Queen in Right of Canada, 2017. Catalogue No. CW69-14/385-2018E-PDF ISBN 978-0-660-26734-0 COSEWIC Assessment Summary Assessment Summary – November 2017 Common name Prairie Skink Scientific name Plestiodon septentrionalis 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. Occurrence Manitoba Status history Designated Special Concern in April 1989. Status re-examined and designated Endangered in May 2004. Status re- examined and designated Special Concern in November 2017. iii COSEWIC Executive Summary Prairie Skink Plestiodon septentrionalis Wildlife Species Description and Significance Prairie Skink is a small, slender lizard with body (snout-vent) length up to 85 mm; the tail can be approximately as long as the body. Prairie Skink is brown with four light stripes along the length of the body and extending onto the tail. Males have reddish orange colouration on the head and throat during the breeding season, and juveniles have bright blue tails. There are three subspecies, but only Northern Prairie Skink occurs in Canada. Northern Prairie Skink’s complete association with the mixed-grass prairie sandhill ecosystems of southwestern Manitoba make it an indicator of this rare landform. Distribution Globally, Prairie Skink occurs in a narrow band from southern Manitoba south to coastal Texas with the distribution of the Northern Prairie Skink subspecies extending south to Kansas. In Canada, its distribution is limited to a small area of southwestern Manitoba in the Brandon and Lauder sandhills. It is disjunct from populations in the United States, separated by approximately 125 km. Habitat Prairie Skink is associated with mixed-grass prairies and savannas and limited to areas with sandy soils. The skinks require heterogeneous habitat structure for foraging and nesting. Such habitats provide a range of temperatures for thermoregulation, gestation and incubation, and for shelter from predators. The skinks preferentially select warm micro-sites with cover objects and leaf litter. In Manitoba, the skinks occur in mixed-grass prairie with patches of grasses/shrubs or open areas near forest edges. They also use edges of deciduous and mixed-wood forest and have been documented to move through these forest types. iv Biology Prairie Skinks spend over seven months of the year (September – April) in hibernation. They burrow beneath the frost line in sandy soils for overwintering. In Manitoba, they become active in mid- to late April and breed in spring. Home ranges are fairly small (typically <100 m in greatest dimension). Females lay a clutch of 1 – 18 eggs (~5 eggs on average) from late June to early July and remain with the eggs until hatching in late July or early August. The young reach sexual maturity at 1 – 3 years and can live up to approximately seven years of age. The generation time is thought to be 3 – 5 years. Prairie Skinks are prey for a variety of birds, mammals, and snakes. If captured by a predator, they can detach their tail as a defence mechanism. The severed tail can twitch and move for over 15 minutes, giving the skink time to escape. Prairie Skinks feed on a variety of invertebrates, with crickets and spiders being common food items. Population Sizes and Trends Estimating the size of the Canadian population is challenging because the full extent of the species’ distribution is incompletely known, the distribution is patchy, and densities vary greatly among sites and years. Extrapolation from density estimates from mark- recapture studies suggests that the population probably consists of at least 10,000 adults with ~98% of the population in the Brandon Sandhills and the remainder in the Lauder Sandhills. Limited information suggests that declines might have occurred at monitored sites in the Brandon Sandhills between 1989 and 2007, but broad scale population trends within the past three generations are unknown. Approximately 28% of the species’ Canadian distribution and 20% of the proposed Critical Habitat under the Species at Risk Act are located within CFB Shilo, where the skinks are currently afforded protection from habitat modification and military training activities. As the species is conservation dependent and requires active habitat management over a significant proportion of its small Canadian range and the main threats to mixed-grass prairie habitat persist, the population could decline if the current level of protection is not maintained and threats across its distribution are not adequately mitigated. Threats and Limiting Factors Prairie Skinks are at the northern limits of their distribution in southern Manitoba and are habitat specialists, increasing their inherent vulnerability to perturbations. The major threats to Prairie Skinks are habitat degradation from invasive plants and vegetation succession of prairie to forest due to fire suppression, and residential development. Roads, railroads, utility and service lines, all-terrain-vehicle trails, grazing, military exercises, and predation by domestic cats may also be threats at some sites. The impact of chemicals applied to crops adjacent to skink habitat and the effect of climate change on skink populations are potential threats but with unknown impacts. Cultivation has destroyed significant amounts of skink habitat in the past, but this threat to new areas has mostly ceased. v Protection, Status and Ranks In Canada, Prairie Skink is listed federally as Endangered and is in Schedule 1 under the Species at Risk Act. In Manitoba, the species is also listed as Endangered under the provincial Endangered Species and Ecosystems Act. A recovery strategy has been proposed as part of national-level planning in Canada. Provincially, a draft Manitoba provincial action plan and recovery strategy have been prepared. Globally, the Prairie Skink’s IUCN status is Least Concern. A significant portion of suitable Prairie Skink habitat occurs on protected lands in Canadian Forces Base Shilo (28%) and Spruce Woods Provincial Park (13%). However, while the land in these areas may be protected from development, threats from invasive plants, vegetation succession, and soil compaction still exist. vi TECHNICAL SUMMARY Plestiodon septentrionalis Prairie Skink Scinque des prairies Range of occurrence in Canada (province/territory/ocean): Manitoba Demographic Information Generation time (usually average age of parents in 3 – 5 years the population; indicate if another method of estimating generation time indicated in the IUCN guidelines (2011) is being used). Is there an [observed, inferred, or projected] Yes, observed and projected decline. Eight continuing decline in number of mature individuals? element occurrences are now probably extirpated, which suggests past declines, but the timing of the declines is uncertain. Habitat succession and invasive plant species are ongoing threats and could result in continued