Sceloporus occidentalis
(Western Fence Lizard)

Key Characteristics

Large spiny scales dorsally

Spiny scales on the posterior of the thighs

Blue patches on the throat and stomach
(more vivid in males)

General Description:
Western Fence Lizards have overlapping, pointed scales that are the source for the common genus name, the Spiny Lizards.  These "spiny" scales are more pronounced on Western Fence Lizards than they are on Sagebrush Lizards.   Western Fence Lizards have these spiny scales on their backs and limbs, even on the posterior of their legs, which is not the case with Sagebrush Lizards the other Sceloporus species (they have granular scales on the posterior of their thighs), (Nussbaum et al. 1983).  Western Fence Lizards can have a range of dorsal ground coloration that is usually some shade of gray, tan or brown.  These lizards can lighten or darken the ground color to some degree, and some individuals are black.  The ground color is broken by a series of wavy dark transverse lines or blotches.  These blotches are more obvious on light colored lizards (females and juveniles are usually a lighter color than males).  Male Western Fence Lizards vary in coloration from females and juveniles in another ways as well; they have more distinct belly patches and a throat patch, which are usually bordered by black markings, and they have scattered blue or green scales dorsally (Storm and Leonard 1995).  Females and juveniles lack the throat patch and the belly patches are either less prominent or absent.  The posterior of the limbs are colored orange or yellow with black lines.  This coloration helps distinguish Western Fence Lizards from Sagebrush Lizards because the later lack the orange-yellow color on the posterior of the limbs.

Western Fence Lizards are medium-sized lizards that are larger than their Idaho congener the Sagebrush Lizard.  Western Fence Lizards can attain sizes of around 99 mm snout-vent length (3.9 in.) and 213 mm (8.4 in.) total length (Storm and Leonard 1995).  The total length is comprised of a tail that is approximately 1.5 times the snout-vent length (Nussbaum et al. 1983), unless of course the tail is regenerating, as these lizards will readily lose their tail.

Western Fence Lizards mate in the spring laying 3-17 eggs (usually 8) between June and July, which hatch in August (Nussbaum et al. 1983).  Juveniles are similar in appearance to adult females.

Western Fence Lizards occupy a variety of habitats that usually have a vertical component, and they avoid dense, moist forests and low flat desert valleys (Nussbaum et al. 1983).   In western Idaho, they are usually found in association with rock outcroppings, talus slopes and cliff faces, they can however also be found in open forested areas on rocks, logs and trees.

Idaho Distribution:
Western Fence Lizard are distributed in Idaho across the lower, western half of the state.  From central Idaho, south through Nevada, and west to Pacific Coast.

Eats beetles, flies, caterpillars, ants, other insects, and spiders.

HibernatesClick word for definition/aestivatesClick word for definition. Inactive during cold weather. Duration of inactive period varies with local climate. Emerges from hibernaculaClick word for definition in late winter or early spring (in Northwest, length of activity varies greatly according to local climatic conditions, but is generally from February to October). Adult males defend home range during breeding season (in California, seasonal home range is generally much less than 0.01 ha). Predators include raptors, snakes, and shrews.

Female lays eggs from April or May to June or July. Clutch size varies from 3-17 eggs; largest females produce largest clutches. Female may produce more than 1 clutch/yr in some areas (in Northwest, females are thought to lay single clutch). Eggs hatch in about 2 mo. Adults first breed in spring of second year.



Unprotected nongame species

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Important State References:
Diller, L.V. and D.R. Johnson. 1982. Ecology of reptiles in the Snake River Birds of Prey Area. USDI Bur. Land Manage. Snake River Birds of Prey Research Project, Boise. 107pp.

Species description, key characteristics and original work by John Cossel Jr. © 1997
Species ecological information from Groves et al. ©1997.
Original images provided by Charles R. Peterson.© 1998
Design and Optimization by Ean Harker©1999, 2000.
DAI layout by Stephen Burton, and Mike Legler © 1999.