San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
Western Fence Lizard, photographed by Jim Melli

Sceloporus occidentalis
Western Fence Lizard

PHRYSONOMATIDAE

Sceloporus from the Greek skelos, meaning leg and porus, meaning pores in reference to their femoral pores located along the underside of the leg. The name occidentalis refers to their western distribution. The species as a whole (S. occidentalis) is called the Western Fence Lizard. These lizards are more commonly called "Blue-bellies" or "Swifts."

Description

The Western Fence Lizard measures 3 1/2 inches (snout-vent length), and is about six inches in total length.

Coloration ranges from light gray to black with dark blotches on the back that continue down the tail. Male Western Fence Lizards have bright blue, sometimes greenish, bellies, and the undersides of their legs are yellow. Females lack this decorative coloring. The scales are keeled and somewhat spiny.

Subspecies: There are as many as five subspecies. Only the San Joaquine Fence Lizard (S. o. biseriatus) and the Channel Islands Fence Lizard (S. o. becki) occur in our region.

Range and Habitat

Western Fence Lizards may reduce the incidence of Lyme Disease in their range! It has recently been discovered that when infected ticks feed on the blood of these lizards, the Lyme disease spirochetes they carry are destroyed. In areas with Western Fence Lizards, about 5 percent of ticks carry the disease, while in other areas 50 percent of ticks harbor the disease.
—Reported by the NY Times News Service, April 19, 1998.

The Western Fence Lizard is distributed throughout eastern Oregon, southwest Idaho, all of Nevada, western Utah, Southern California, and northwestern Baja California. A disjunct population occurs on Isla de Cedros; a Pacific Ocean island off of Baja California.

It is commonly found from the coast to the highest mountain areas at over 6,000 feet. It isn't found in the desert. This lizard is conspicuous and common in its range. It thrives in a wide variety of habitats, ranging from coastal sage scrub and chaparral on the coast and foothills, to the forests of higher elevations. It's usually found on or near the ground, in rock and wood piles, tree trunks, and the lower branches of shrubs.

Natural History

Behavior: This aptly named lizard enjoys sitting on prominent points, like fence posts, where it can sun itself, and watch for food and predators. Like many species of lizards, this one is able to change its general coloration to match its background. Light colored lizards placed on dark rocks become a darker color. Interestingly, some lizards remain dark when placed on a light background, mimicking a shadow cast by an imperfection or crack in the rock surface.

Prey and Predators: Its diet consists of insects and various other arthropods. Unfortunately, its love of high places makes it easy prey for snakes, hawks, and predaceous mammals. Kingsnakes and Striped Racers are particularly fond of fence lizards. The Western Fence Lizard avoids danger through constant vigilance and fast reflexes.

Breeding: Mating occurs in May or June. As many as ten eggs per clutch can be laid as early as July, producing hatchlings as early as mid-August. Upon hatching, the little ones measure about 2 1/4 inches in total length.

Did you know...

The bright blue patches along the sides of the body of the male give this lizard the common name of "Blue-belly."

Conservation Status

There has been no proposed conservation plans.


Text by Dick Schwenkmeyer.
Photo by Jim Melli.

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