A Guide to the Amphibians
and Reptiles of California

Skilton's Skink - Plestiodon skiltonianus skiltonianus

Baird and Girard, 1852

(= Eumeces skiltonianus skiltonianus)

Click on a picture for a larger view

Range in California: Red & Gray

Blue: Coronado Skink
Gray: Intergrades

Adult, Modoc County

Adult, Siskiyou County

Adult, Modoc County

Adult, Glenn County

Adult, Santa Clara County

Adult with orange breeding color on chin, Humboldt County

Adult showing orange breeding color, February, Santa Clara County

Underside of a breeding adult, San Bernardino County, showing the orange
breeding coloring.

Adult with orange breeding color, San Luis Obispo County

Adult with long intact tail found basking on streamside rocks in Trinity County

Adult with orange breeding color, Sutter Buttes, Sutter County. © Jackson Shedd.
Specimen courtesy of Eric Olson.

Adult, Contra Costa County

Adult, Ventura County, © Patrick Briggs

Adult, Humboldt County. When this skink was discovered hiding under an object, it ran off, jumped into the water and quickly swam to get away.
© Robert Mellinger

Adult with orange breeding color on head, Del Norte County © Alan Barron

Adult found along the American River in Rancho Cordova, Sacramento County.
© Brandon Hunsberger

Adult found near Anza,
Riverside County © Curtis Croulet

These adult skinks from the Palos Verdes Peninsula in Los Angeles County have a paler body color than most. This color phase has been described as common in that area by the photographer. © Andrew Louros

This is a more typically-colored skink from the Palos Verdes Peninsula for comparison with the paler skinks to the left. © Andrew Louros

Adult, Orange County © Tadd Kraft

These two skinks were found under the same board in San Luis Obispo County. The one on the left was found three weeks earlier than the
one on the right, which was found the first week of March, having just developed its bright orange breeding coloring. © Joel A. Germond

Subadult, San Luis Obispo County
© Joel A. Germond

This adult Skilton's Skink and Coast Range Fence Lizard were observed basking together frequently in a backyard garden in Marin County in April. This might represent a mate-guarding behavior by a male skink that confused the fence lizard for a female skink, or maybe they're just sharing a good basking spot, unconcerned about any threat from the other lizard.

Adult Coronado Skink, San Diego County © Jack

You can see in this distant shot how much the blue tail on a skink stands out. The light stripes and dark background on the head and body tend to blend into the background making them less noticable. When a skink with a blue tail is running, it can look like there is a small bright blue snake wriggling instead of a lizard. That will attract the eye of a predato. But unlike the body, the tail is expendable. If a predator grabs it, it will come off easily but it will still move as if it is alive to distract the predator while the rest of the lizard gets away unharmed.

Toothy Skinks, genus Plestiodon, have smooth shiny cycloid scales that are reinforced with bone.
Plestiodon skiltonianus is shown here.

Juveniles

Juvenile, Contra Costa County

Juvenile, Napa County

Juvenile, Sonoma County © Lou Silva

Juvenile, Tuolumne County

Comparison of juvenile skinks:
Top: P. s. skiltonianus - Modoc County
Bottom: P. gilberti - Kings County
© Patrick Briggs

Breeding Adults

These adult skinks (presumably a male and a female) were observed in courting behaviour at the edge of a trail in Santa Clara County. The male chased the female in and out of a crack in some bark, across the trail, and over various branches and logs.
© Wim de Groot

Identification of the Two Subspecies of Plestiodon skiltonianus

The majority of Skilton Skinks -
P. s. skiltionianus, have an interparietal that is not enclosed by the parietals. (Tanner 1957¹ )

The majority of Coronado Island Skinks - P. s. interparietalis, have an interparietal that is enclosed by the parietals.
(Tanner 1957¹ )

Comparison of Western Skinks with Gilbert's Skinks (Plestiodon skiltonianus and Plestiodon gilberti)

Note that the dark stripes on the sides of the tail on the Western Skink extend far onto the tail unlike the stripes on juvenile Gilbert's Skinks. Compare

More information about the differences between Gilbert's Skinks and Western Skinks.

Western Skinks usually have 7 supralabial scales.

Compare with Gilbert's Skinks, which usually have 8 supralabials.

Habitat

Mixed coniferous forest habitat,
Santa Clara County

Rocky habitat along ridgeline in chaparral grassland,
Contra Costa County

Riparian woodland/grassland Habitat, Contra Costa County

Rocky mixed woodland montane Habitat, Napa County

Habitat, coastal mixed woodlands/grasslands Monterey County

Habitat, forest clearing,
Humboldt County

Mixed woodland/grassland habitat next to a reservoir, Contra Costa County

Streamside habitat in coniferous forest, Mendocino County (found wintering under bark on downed tree.)

Montane habitat, 6,200 ft., San Bernardino County

Habitat, 1,100 ft. Fresno County.

Habitat, 2,600 ft., Trinity County

Sandy coastal habitat,
San Luis Obispo County

Short Videos

A skink is found under a rock. It bites hard, refusing to let go, then finally runs through dry grass with typical serpentine motion.

A juvenile skink loses its blue tail, which writhes around on the ground. This is a defensive measure used to distract the predator which caused the tail to become detached from the rest of the lizard as it tries to escape.

In this video you can see how the blue tail on a juvenile skink stands out when the lizard moves, especially when it uses its stripes to blend into the vegetation. A predator is more likely to go for the tail, which can detach without hurting the lizard.

A big adult skink found under a rock in winter in Contra Costa County.

Two male Skilton's Skinks fight over territory during the breeding season on a day in early May in Skamania County, Washington. One bites the other on the head and cannot be shaken off.
© Chris Rombough

Description

Size

2 1/8 - 3 2/5 inches long from snout to vent (5.4 - 8.6 cm) and aproximately 7.5 inches in total length.

Appearance

A small skink with a slim body, small head, thick neck, small legs, and a smooth, shiny body with cycloid scales.

Color and Pattern

Striped with 3 dark brown and light cream stripes:
A wide dark brown stripe, edged with black, extends from the nose to the tail down the middle of the back,
bordered by two pale stripes which extend from the nose over the eye to the tail.
Two more very dark stripes extend down each side through the eyes, to the tail, where they extend well out onto the tail.
Two more pale stripes extend below these dark side stripes.
The underside is pale or gray.
The tail is gray or dull blue on older adults. Younger adults often retain some of the bright blue coloring.

"In the breeding season reddish or orange color appears on side of head and chin and occasionally on sides, tip, and underside of tail." (Stebbins, 2003)

Young

Tail is bright blue on juveniles.
The stripes on juveniles are more highly contrasted than on adults.

Characteristics of Subspecies of Plestiodon skiltonianus (from ¹ Tanner 1957)

P. s. interparietalis - Coronado Skink

"Interparietal enclosed by the parietals in 80 per cent of the population.
Stripes of the body pattern extended onto anterior half or more of tail."

"The extension of the striped pattern on the tail is also seen in specimens of skiltonianus from the coastal ranges of California. However, specimens from north of San Diego County are generally less obviously striped on the tail and if so then with only an occasional one having the interparietal enclosed."

"Diagnosis: this form is most closely related to typical skiltonianus with which it intergrades in San Diego and Riverside counties California. It is different to all other skiltonianus in having the interparietal reduced in size and enclosed posteriorly by the parietals,
the medial and lateral dark stripes extend from the body to or beyond the middle of the tail."

P. s. skiltonianus - Skilton's Skink

"Interparietal rarely enclosed by the parietals. Usually less than 10 per cent even in Los Angeles and San Bernardino Counties; and/or stripes of body pattern not extended on more than the base of the tail."

P. s. utahensis - Great Basin Skink

"Dorsolateral stripe occupying more than half of the second scale row and being nearly one half the diameter of the dark dorsal interspace.
Dark stripe below lateral light stripe rarely present.
Diameter of the dorsolateral stripe usually greater than the length of the first nuchal."

Identifying Skinks in California - Differences between Western Skinks and Gilbert's Skinks (Plestiodon skiltonianus and Plestiodon gilberti)

Life History and Behavior

Activity

Diurnal, but secretive and not typically seen active.
Occasionally seen foraging in leaf litter.
More commonly found underneath bark and surface objects, especially rocks, where it lives in extensive burrows.
Inactive in cold weather.

Defense

The tail is easily broken off.
When detached, it writhes back and forth to distract a predator while the lizard escapes.
The lizard will grow a new tail.
The bright blue coloring on the tail of a juvenile skink tends to distract a predator from the main body of the lizard.
Sometimes only the blue tail can be seen as the lizard rushes through grass or leaves.
Occasionally the blue tail is mistaken for a small blue snake.

Diet and Feeding

Insects, and other small invertebrates, especially spiders and sow bugs.

Breeding

Females lay 2 - 10 eggs in June and July.
Females guard their eggs until they hatch.
Eggs hatch in late July and August.

Habitat

Grassland, woodlands, pine forests, sagebrush, chaparral, especially in open sunny areas such as clearings and the edges of creeks and rivers.
Prefers rocky areas near streams with lots of vegetation. Also found in areas away from water.

Geographical Range

In California, this subspecies is found throughout the northern part of the state, and in the northern Sierra Nevada and foothills, in the north and south coast mountain ranges, extending south to coastal San Diego County where P. s. interparietalis takes over.

It is also found in the southern Sierra Nevada on the Kern Plateau, the Greenhorn and Piute mountains, Mt. Breckenridge, Caliente Creek, and east of the Sierra Nevada in isolated locations, including the Bodie Hills, the White Mountains, and on the east slope of the Sierra Nevada at Olancha.

Not present in the southern deserts and much of the central valleys.

Also present on Santa Catalina Island. (Jones, Lawrence, Rob Lovich, 2009, shows P. s. interparietalis inhabiting Santa Catalina Island, but the Santa Barbara Museum of Natural History has a specimen from the island labelled P. s. skiltonianus, and for that reason I show P. s. skiltonianus inhabiting the island instead of P. s. interparietalis.)

The species Plestiodon skiltonianus ranges beyond California north into inland British Columbia, east into Idaho, Nevada, Utah, and northcentral Arizona, and south to the southern tip of Baja California.

¹ Tanner 1957 describes some intergrade areas: "Intergrades skiltonianus x interparietalis; San Diego Co.: Escondido; Oceanside; Poway."

Elevational Range

From sea level up to around 8,300 ft. (2,530 meters).

Notes on Taxonomy

Currently, several subspecies of Eumeces skiltonianus are recognized, including P. s. utahensis, and P. s. interparietalis.

Some taxonomists do not recognize the southern California subspecies P. s. interparietalis. They group it with P. s. skiltonianus.

Brandley et al. (2005 Syst. Biol. 54:373-390) replaced Eumeces with Plestiodon.

The Society for the Study of Amphibians and Reptiles has adopted the use of Plestiodon in the sixth edition of their Scientific and Standard English Names of Amphibians and Reptiles of North America north of Mexico list.

Jonathan Q. Richmond, and Tod W. Reeder, in their 2002 paper * list one specimem from the San Diego State University collection (SDSU 3816) utahensis CA, Inyo Co., Independence Creek at Gray’s Meadow campsite. 36 47.2N, 118 15.2W) that comes from an area fairly far south of the Nevada border on the eastern slope of the Sierra Nevada Mountains just east of Independence as E. s. utahensis, Great Basin Skink. The Museum of Vertebrate Zoology at UC Berkeley has specimens of P. skiltionianus (with no subspecies indicated) from Inyo County including Gray's Meadow and another location east of Independence the White Mountains, and the White Mountains. If the SDSU specimen identification is correct, it is possible that this subspecies ranges in an isolated region east of Independence and in the White Mountains.

Alternate and Previous Names (Synonyms)

Eumeces skiltonianus skiltonianus - Skilton's Skink (Stebbins 2003)
Eumeces skiltonianus skiltonianus - Western Skink (Stebbins 1966)
Eumeces skiltonianus - Common Western Skink (Smith 1946)

Conservation Issues (Conservation Status)

None

Taxonomy
Family	Scincidae	Skinks	Gray, 1825
Genus	Plestiodon (formerly Eumeces)	Toothy Skinks	Duméril and Bibron, 1839
Species	skiltonianus	Western Skink	Baird and Girard, 1852
Subspecies	skitonianus	Skilton's Skink	Baird and Girard, 1852
Original Description
Eumeces skiltonianus - (Baird and Girard, 1852) - Proc. Acad. Nat. Sci. Philadelphia, Vol. 6, p. 69 from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz
Meaning of the Scientific Name
(Eumeces - Greek - eu- good or nice and mekos length or height) Plestiodon = ? skiltonianus - honors Skilton, Avery J. from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
Related or Similar California Lizards
P. g. cancellosus - Variegated Skink P. g. gilberti - Greater Brown Skink P. g. placerensis - Northern Brown Skink P. g. rubricaudatus - Western Red-tailed Skink P. s. interparietalis - Coronado Skink
More Information and References
California Department of Fish and Wildlife ¹ Tanner, Wilmer W. A taxonomic and ecological study of the western skink (Eumeces skiltonianus). Great Basin Naturalist 17:59-94 1957. Stebbins, Robert C., and McGinnis, Samuel M. Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012. Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972. Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Turtles and Lizards of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009. Jones, Lawrence, Rob Lovich, editors. Lizards of the American Southwest: A Photographic Field Guide. Rio Nuevo Publishers, 2009. Smith, Hobart M. Handbook of Lizards, Lizards of the United States and of Canada. Cornell University Press, 1946. Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003. Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992. Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998. Brown et. al. Reptiles of Washington and Oregon. Seattle Audubon Society,1995. Nussbaum, R. A., E. D. Brodie Jr., and R. M. Storm. Amphibians and Reptiles of the Pacific Northwest. Moscow, Idaho: University Press of Idaho, 1983. St. John, Alan D. Reptiles of the Northwest: Alaska to California; Rockies to the Coast. Lone Pine Publishing, 2002. Lemm, Jeffrey. Field Guide to Amphibians and Reptiles of the San Diego Region (California Natural History Guides). University of California Press, 2006. * Jonathan Q. Richmond, and Tod W. Reeder. EVIDENCE FOR PARALLEL ECOLOGICAL SPECIATION IN SCINCID LIZARDS OF THE EUMECES SKILTONIANUS SPECIES GROUP (SQUAMATA: SCINCIDAE) Evolution, 56(7), 2002, pp. 1498–1513

Conservation Status
The following conservation status listings for this animal are taken from the August 2019 California Natural Diversity Database (CNDDB) Special Animals List and the CNDDB 2019 Endangered and Threatened Animals List, both of which are published by the California Department of Fish and Wildlife. The status listings here might not be the most current. Check the CDFW CNDDB website to see if there are more current lists: https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals If no status is listed here, the animal is not included on either CDFW CNDDB list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status, you can go to the NatureServe and IUCN websites to check their rankings. This animal is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.
Organization	Status Listing	Notes
NatureServe Global Ranking
NatureServe State Ranking
U.S. Endangered Species Act (ESA)	None
California Endangered Species Act (CESA)	None
California Department of Fish and Wildlife	None
Bureau of Land Management	None
USDA Forest Service	None
IUCN

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