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Western Skink

Plestiodon skiltonianus

Family: Scincidae

COSEWIC status:
  • Special Concern
SARA status:
  • Special Concern
IUCN status:
  • Least Concern

Description

The Western Skink is a medium-sized lizard that can grow to over 20 cm in total length, but most individuals are much smaller. They have smooth, shiny scales, a pointed head, and short legs characteristic of skinks. Four longitudinal, light-coloured stripes extend from the head to the base of the tail. The stripes contrast with the dark-coloured, brown back and grey or black sides. The tail, often vividly coloured in juveniles, remains blue through adulthood. The belly is light grey or cream coloured.

Similar Species

In parts of its range, the Western Skink overlaps with the Northern Alligator Lizard. Western Skinks are distinguished by smaller body size, smoother scales, distinct stripes along the body and their bright blue tail, particularly among juveniles.

Distribution

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The species reaches the northern limit of its continental distribution in south-central British Columbia. Its range is restricted to a small portion of British Columbia between Kootenay Lake in the east and Princeton in the west. One recent sighting and an older listing indicate that the species might also inhabit Vancouver Island, but its persistence there remains unconfirmed. The North American range extends from British Columbia to the southern tip of Baja California, and from the Pacific coast in Oregon to western Montana, Idaho, and Utah.

Habitat

The Western Skink is found in a wide range of habitats, including dry woodland, grassland, along the banks of creeks, and in forest clearings. Important habitat attributes include herbaceous vegetation cover for foraging and predator avoidance, loose soil for burrow excavation, and abundance of rocks or downed logs for shelter. Basking typically occurs in areas that provide shelter, such as crevices or under rocks. Although individuals are often found within or along forest edges, their association with forests is unclear. Nests are typically located under rocks, and the chambers can extend several centimetres underground. Individuals require access to rock crevices below the frost line for hibernation. They have small home ranges and exhibit high site fidelity; individuals are typically recaptured within 10 metres of a previous capture, both within a summer season and from year to year. Movements of greater than 100 metres are rare.

Biology

In British Columbia, Western Skinks emerge from hibernation in mid-April. Mating takes place shortly thereafter and females lay one clutch of 2–6 eggs in June or July. Females remain with the eggs until hatchling to protect them from predators and will move them around the nest to optimize heat and moisture conditions for egg development. Eggs hatch from mid-August to early September and the young reach sexual maturity at 2–3 years of age. Little information is available on lifespan in this species, but the maximum is likely around 9 years. Western Skinks consume a variety of invertebrates (e.g., caterpillars, moths, beetles, grasshoppers, spiders, isopods, and crickets) as well as the eggs of these animals. Western Skinks spend much of their time in retreat sites and are uncommon in the open. Individuals enter hibernation in late-September. In Creston, B.C., hibernation occurs in the summer habitat with no seasonal migration, although movement away from hibernation sites has been reported for some U.S. populations. Individuals may autotomize (drop) their tail as a defensive strategy to distract a predator; tail autotomy is particularly common among juveniles. Although the tail will grow back over time, this is energetically costly and may negatively affect growth and survival.

Threats

The greatest immediate threat to the Western Skink is habitat alteration and fragmentation associated with an increasing human population, including residential development, road construction, and talus extraction. Factors that increase the vulnerability of the species in Canada include a small geographic range in areas with high human density, limited dispersal capability, and increasing pressures on habitats. Predation by domestic and feral pets, especially cats, is a growing threat in many areas. There is likely little road mortality, although roads may act as barriers.

Additional Information About This Species In Canada