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A Guide to the Amphibians
and Reptiles of California


Coronado Skink - Plestiodon skiltonianus interparietalis

(Tanner, 1958 “1957”)

(= Eumeces skiltonianus interparietalis)
Click on a picture for a larger view



Western Skink California Range MapRange in California: Blue & Gray

Red: Skilton's Skink
Gray: Intergrades


observation link





Coronado Skink
Coronado Skink Coronado Skink
  Adult, San Diego County  
sCoronado Skink Coronado Skink Coronado Skink
Adult, San Diego County Adult, San Diego County Adult, San Diego County
Coronado Skink Coronado Skink Coronado Skink
Adult, underside, San Diego County Adult, San Diego County Adult, San Diego County
Coronado Skink Coronado Skink  
This skink was found underneath a rock, lying on top of her eggs, in San Diego County. © Ryan Sikola. Adult, San Diego County © Jack

You can see in this distant shot how the blue tail stands out when a skink runs. The light stripes and dark background often blend into the backround with sticks and leaves rendering the head and body almost invisible, leaving people sometimes to think that they are seeing a small "neon blue" snake wriggling through the grass or leaves.
 
     
Juveniles
Coronado Skink Coronado Skink Coronado Skink
Juvenile, found in and pulled out of a swimming pool in
San Diego County.  © Sean Kelly
Another juvenile, found in and pulled out of a swimming pool in San Diego County.
© Sean Kelly
     
Identification
Coronado Skink Great Basin Collared Lizard
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 Skinks, which usually have 8 supralabials.
Toothy Skinks, genus Plestiodon, have smooth shiny cycloid scales that are reinforced with bone. Plestiodon skiltonianus is shown here.

Coronado Skink Coronado Skink  
The majority of Skilton Skinks - P. s. skiltionianus, have an interparietal that is not enclosed by the parietals. (from Tanner 19571 ) The majority of Coronado Island Skinks - P. s. interparietalis, have an interparietal that is enclosed by the parietals. (from Tanner 19571 )  
     
Short Videos of Western Skinks, Skilton's Skink Subspecies
Skilton's Skink Skilton's Skink Tail Skilton's Skink
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.
  Skilton's Skink  
  A big adult skink found under a rock in winter in Contra Costa County.  
     
Habitat
Coronado Skink Habitat Coronado Skink Habitat Coronado Skink Habitat
Habitat, coastal sage scrub hilltop,
San Diego County
Habitat, coastal valley, San Diego County Habitat, coastal valley, San Diego County
San Diego Ring-necked Snake Habitat San Diego Mountain Kingsnake Habitat Red Diamond Rattlesnake Habitat
San Diego County coastal sage habitat Habitat, 5,500 ft. San Diego County Habitat, hill next to suburbs,
San Diego County
   
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.

During the breeding season, adults develop reddish orange coloring on the side of head, chin, on the tail, and sometimes the sides.
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.
Young
The stripes on juveniles are more highly contrasted than on adults.
The tail is bright blue on juveniles.

Characteristics of Subspecies of Plestiodon skiltonianus   (from Tanner 19571 )
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
 
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.

Geographical Range
This subspecies is found in inland Southern California south through the north Pacific coast region of northern Baja California Norte.

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, in his1957 description of the subspecies, describes the range as
"North and western Baja California including the Coronado and Todos Santos Islands, and southern San Diego County, California."

Specimens examined in the study are described below, but he does not say which of the examined specimens keyed out to interparietalis.

Riverside County: San Jacinto, Andreas Canyon S of Palm Springs; Snow Creek; Palm Springs.
San Diego County: Barona Ranch Alpine, Dulzura, El Capitan, Laguna Mts, San Diego, Palomar Mts

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

Based on that information, my map shows a wide intergrade area from Oceanside northeast across the range into Riverside County down to Poway. That's the best I can do with the information given until I find more information or they get rid of the subspecies (which is more likely to happen.)

To further confuse the issue, I have reproduced a detail of the localities map from 2 Jennings and Hayes,1994 study of California Species of Special Concern. They show P. s. interparietalis present in a large area of Riverside County.
Western Skink California Range Map
Western Skink California Range Map
Range map showing subspecies skiltonianus (boomerangs - top) and interparietalis (stripes - bottom).
This appears to be the basis of most of the range maps showing where the two subspecies meet in San Diego and Riverside Counties. 1 Tanner 1957
(Click map for a larger version)  

Localities for E. s. interparietalis from
2 Jennings and Hayes,1994.
(Click map for a larger version)
Full Species Range Map
Elevational Range
From sea level up to around 8,300 ft. (2,530 meters).

Habitat
Grassland, woodlands, pine forests, 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.

Notes on Taxonomy
"Type: California Academy of Sciences No. 13576, an adult male, collected on South Coronado Island, Baja California 7 April 1908, by Rollo Beck."  1 Tanner,1957

Currently, several subspecies of P. 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.


Alternate and Previous Names (Synonyms)

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

Conservation Issues  (Conservation Status)
A California species of special concern due to habitat loss.
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

interparietalis Coronado Skink (Tanner, 1958 “1957”)
Original Description
Eumeces skiltonianus - (Baird and Girard, 1852) - Proc. Acad. Nat. Sci. Philadelphia, Vol. 6, p. 69
Eumeces skiltonianus interparietalis - Tanner, "1957" 1958 - Great Basin Naturalist, Vol. 17, p. 73

from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz

The Common Name "Coronado Skink" refers to the origin of the type specimen:
Type: California Academy of Sciences No. 13576, an adult male, collected on South Coronado Island, Baja California, Mexico, 7 April 1908, by Rollo Beck.

Meaning of the Scientific Name
(Eumeces - Greek - eu- good or nice and mekos length or height)
Plestiodon = ?

skiltonianus
- honors Skilton, Avery J.
interparietalis - Latin - inter - between, and parietalis - pertaining to walls

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. skiltonianus - Skilton's 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.

2 Mark R. Jennings, and Marc P. Hayes. Amphibian and Reptile Species of Special Concern in California.
California Department of Fish and Game study, 1994

Lemm, Jeffrey. Field Guide to Amphibians and Reptiles of the San Diego Region (California Natural History Guides). University of California Press, 2006.

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.

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.

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.


Conservation Status

The following status listings come from the Special Animals List and the Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.


This subspecies is listed, not the full species.
Organization
Status Listing
NatureServe Global Ranking G5T2T3Q

The species is Secure—common; widespread and abundant.
The subspecies is Imperiled - Vulnerable, but there are taxonomic questions associated with it.

NatureServe State Ranking S1S2 Critically Imperiled - Imperiled
U.S. Endangered Species Act (ESA) None
California Endangered Species Act (CESA) None
California Department of Fish and Wildlife WL Watch List
Bureau of Land Management S Sensitive
USDA Forest Service None
IUCN Not listed


 

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