The Western fence lizard (Sceloporus occidentalis) is a common lizard found in the western United States and northwestern Mexico. As the ventral abdomen of an adult is characteristically blue, it is also known as the blue-belly.
The Western fence lizard is brown to black in color (the brown may be sandy or greenish) and has black stripes on its back, but its most distinguishing characteristic is its bright blue belly. The ventral sides of the limbs are yellow. These lizards also have blue patches on their throats. This bright coloration is faint or absent in both females and juveniles. In some populations, the males also have iridescent, bright turquoise blue spots on the dorsal surface.
Western fence lizards are found in California, eastern and southwestern Oregon (some populations are found even north of Seattle, Washington), as well as in the Columbia River Gorge, southwestern Idaho, Nevada, western Utah, northwestern Baja California, Arizona, and some of the islands off the coast of both California and Baja California. There is also an isolated population in the Northwestern Tualatin Valley, around Henry Hagg Lake. These lizards occupy a variety of habitats. They are found in grassland, broken chaparral, sagebrush, woodland, coniferous forest, and farmland. They generally avoid the harsh desert and are often found near water.
Western fence lizards lead a solitary life. They are diurnal reptiles and are commonly seen sunning on paths, rocks, fence posts, and other high places, which makes them easy prey for birds and even some mammals, such as shrews. During the cold morning, they also can be prey for Alligator lizards. Western fence lizards protect themselves by employing their fast reflexes, including biting and possibly defecating on the predator. They can change color from light grey or tan to nearly jet black, but they probably use this ability for the purpose of thermoregulation while basking and not as a means to camouflage themselves. Like most other lizards, they go through a period of hibernation during the winter. The length of time and when they emerge usually varies depending on climate.
Western fence lizards mate in the spring and during this time males are very territorial and defend their home ranges. Females lay 1-3 clutches of 3 to 17 eggs between April and July. The eggs hatch in August. Young Western fence lizards usually do not breed until the spring of their second year.
There are no major threats to this species at present.
According to IUCN, the Western fence lizard is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.