The western skink ''(Plestiodon skiltonianus)'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of small, smooth- scaled lizard with relatively small limbs. It measures about 100 to 210 mm (about 4 to 8.25 inches) in total length (body + tail). It is one of seven species of

lizards in Canada This is a list of the reptiles of Canada. Most species are confined to the southernmost parts of the country. All Canadian reptiles are composed of squamates and testudines. Conservation status - IUCN Red List of Threatened Species: : - Extinc ...

. They spend much of their day basking in the sun. Their diet ranges widely, including spiders and beetles. Western skinks will bite if grasped and will flee if they feel threatened. It is a common but secretive species whose range extends from southern British Columbia and throughout

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. T ...

Nevada Nevada ( ; ) is a state in the Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the 7th-most extensive, ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyomi ...

, and

Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the s ...

and into western

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...

and northern

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

and Missouri. They can also live in some areas of

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

Stebbins RC (1985). ''A Field Guide to Western Reptiles and Amphibians, Second Edition, Revised''. Boston: Houghton Mifflin. 336 pp. It is widespread in northern California but primarily restricted to the coast in central and southern California. Found in a variety of habitats, this lizard is most common in early successional stages or open areas of late successional stages. Heavy brush and densely forested areas are generally avoided. Western skinks are found from sea level to at least 2,130 m (7,000 ft). This diurnal reptile is active during the warm seasons.

Taxonomy

Initially described in 1852 by Baird and Girard, the Western skink is named for Dr. Avery Judd Skilton (1802–1858), an American physician and naturalist, who collected the first specimens. Together with Gilbert's skink (''P. gilberti''), the San Lucan skink (''P. lagunensis''), and the four-lined Asiatic skink (''P. quadrilineatus''), the western skink belongs to the so-called "''skiltonianus'' group". The exact

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

within this group has yet to be conclusively determined, and may need revision following DNA analysis research.

Western skink (plestiodon skiltonianus) - juvenile

There are three recognized subspecies, including the

nominotypical subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

: *Coronado skink, ''P.s. interparietalis'' (W. Tanner, 1957)
Occurs in southern

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

and

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. *Great Basin skink, ''P.s. utahensis'' (W. Tanner, 1957)
Occurs in

. *Skilton's skink, ''P.s. skiltonianus'' Baird & Girard, 1852 The most common is Skilton's skink, which occurs throughout the western

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

west of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...

and in southern

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, Canada.

Behavior

The western skink is a secretive and very agile lizard that

forages Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavi ...

actively through

leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

litter and dense vegetation, preying upon small

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s including

spiders Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species di ...

, a variety of

insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...

and sow bugs.

Cricket Cricket is a bat-and-ball game played between two teams of eleven players on a field at the centre of which is a pitch with a wicket at each end, each comprising two bails balanced on three stumps. The batting side scores runs by str ...

s, beetles, moths, grasshoppers, and other arthropods have been found in the stomachs of skinks. Prey is sometimes stalked and cannibalism has been reported. It is a good burrower and sometimes constructs burrows several times its own body length. Females take great care of their eggs. Western skink females construct nest chambers that are several centimeters deep in loose moist soil. Typically these chambers are located under surface objects, especially flat stones, logs, and sometimes in or near rock outcrops. The females remain guarding the nest until the young leave the nest. Female western skinks will defend their nests from predators, repair their nests, and even bask in the sun and then return to the nest to provide additional heat.

Habitat

Found in a variety of habitats from sea level to at least 2,130 m (7,000 ft), the western skink is commonest in early successional stages or open areas within habitats in which it occurs. Heavy brush and densely forested areas are generally avoided. The western skink seems to prefer a somewhat moist environment, although it can also be found on dry hillsides. Frequents

grassland A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...

, broken chaparral, pinon-juniper and juniper-sage woodland, and open pine-oak and pine forests.Stebbins RC (2003). ''A Field Guide to Western Reptiles and Amphibians, Third Edition''. Peterson Field Guide Series ®. Boston and New York: Houghton Mifflin Company. xii + 533 pp. . (''Eumeces skiltonianus'', pp. 312-314 + Plate36 + Map 110). The soil of its nest chambers is invariably moist. Standing water is apparently not required. Although Western skinks avoid forests, they are found in dry areas within forested areas.

Description

Adult Western skinks have a broad brown stripe down their backs, edged with black and bordered on each side by a conspicuous whitish to beige dorsolateral stripe that begins on nose and extends over the eye and back alongside body onto the tail. A second pale stripe, starting on upper jaw, occurs low on each side and is separated from the first by a broad dark brown or black band originating on the side of head and usually extending well out onto the tail, though this band can be disrupted if the tail is lost and regrown. Juvenile skink's tails are bright blue, turning to grey in adulthood. In the breeding season reddish or orange color appears on the side of head and chin, and occasionally on the sides, tip, and underside of the tail. They usually have seven supralabial scales and four enlarged nuchals. Young skinks' colorations are more vivid than those of adults.

Geographic Range

Western skinks can be found from southern

, Canada, to the tip of the Baja California Peninsula, and throughout most of Great Basin to extreme Northern

; central

to the Pacific Coast. The species is apparently absent from the floor of

San Joaquin Valley The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven ...

(they have been observed in rural areas of southeast Lodi, CA), central Sierra Nevada (except a few scattered locations in the foothills where they are very common), and lowland deserts of

. In Northern Baja, California the species occurs in the northwestern part at least as far south as Colonia Guerro and in the south in the cape and Comondu regions, Santa Agueda, and San Francisco de la Sierra. On Santa Catalina, Los Coronados, and Todos Santos Island off the coast of California.

Predators and Defensive Behavior

Western skinks are hunted by mammalian, avian, and reptilian predators.Ovaska, K.E. and C. Engelstoft. 2002. COSEWIC status report on the western skink Eumeces skiltonianus in Canada, in COSEWIC assessment and status report on the western skink Eumeces skiltonianus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 1-19 pp. In Idaho, their predators include night snakes, striped whipsnakes, and raptors. Young western skinks have a bright blue tail with color that fades with age. Skinks can perform

autotomy Autotomy (from the Greek ''auto-'', "self-" and ''tome'', "severing", αὐτοτομία) or self-amputation, is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude ...

; if seized by a predator its tail is deliberately cast and wriggles violently attracting attention while the lizard may escape. The tail will grow back with time but is often darker in color and misshapen. It will play dead, but this behavior is rarely seen. Juvenile Western Skink (Plestiodon skiltonianus)

Juvenile Western Skink (Plestiodon skiltonianus)

Life History

This skink is diurnal during the period of warm-season activity. During summer most activity is concentrated in the morning and late afternoon. Where summer temperatures are not extreme, activity extends throughout the day. Adult skinks usually become inactive by early fall but juveniles extend their period of activity several weeks. The length of time they are inactive varies depending on the climate of the area. During their hibernation period, western skinks remain in communal dens. The reproductive season for this species varies geographically and from year to year depending on local conditions. Mating probably occurs in the spring soon after emergence. Males turn orange on the underside when they are breeding. Females lay 2–6 eggs during June and July. Western skinks' eggs hatch in the months of July and August; the exact time differs by geographic location. They reach sexual maturity at around 3 years, and live up to 9 years