The western fence lizard (Sceloporus occidentalis) is a species of lizard native to Arizona, New Mexico, and California, as well as Idaho, Nevada, Oregon, Utah, Washington, and Northern Mexico. The species is widely found in its native range and is considered common, often being seen in yards, or as the name implies, on fences. As the ventral abdomen of an adult is characteristically blue, it is also known as the blue-belly. Two western fence lizards have been reported with duplicated or forked tails, presumably following an autotomy.
Taxonomy
Taxonomy for the western fence lizard has been under much debate. S. occidentalis belongs in the order Squamata (snakes and lizards) and the suborder Iguania. The family in which it belongs is still under scrutiny. The family Phrynosomatidae, along with seven other families, used to be included in the single family Iguanidae, until Frost and Etheridge's (1989) analysis of iguanian systematics suggested the family be divided. Most literature, however, still place the phrynosomatids in Iguanidae.
Five subspecies are recognized, as follows:
- San Joaquin fence lizard, Sceloporus occidentalis biseriatus
- Coast Range fence lizard, Sceloporus occidentalis bocourtii
- Great Basin fence lizard, Sceloporus occidentalis longipes
- Northwestern fence lizard, Sceloporus occidentalis occidentalis
- Sierra fence lizard, Sceloporus occidentalis taylori
Some authors have raised the island fence lizard to specific rank, Sceloporus becki. However, recent work in molecular systematics has suggested there are four clades and 11 genetically separable populations, and the subspecies will probably have to be redefined.
Identification
thumb|Male S. o. occidentalis displaying iridescent, bright turquoise and blue coloration. This individual displays a more striking coloration than is usually seen in this species. |alt=Male S. o. occidentalis displaying iridescent, bright turquoise and blue coloration. Most individuals do not exhibit such striking coloration.
Western fence lizards measure (snout-vent length) and a total length of about . They are brown to black in color (the brown may be sandy or greenish) and have black stripes on their backs, but their most distinguishing characteristic is their bright blue bellies. The ventral sides of the limbs are yellow. Male blue belly 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 display iridescent, bright turquoise blue spots on the dorsal surface. The scales of S. occidentalis are sharply keeled, and between the interparietal and rear of thighs, there are 35–57 scales.
The western fence lizard occupies a variety of habitats. It is found in grassland, broken chaparral, sagebrush, woodland, coniferous forest, and farmland, and occupies elevations from sea level to 10,800 ft. In the habitats, the western fence lizard functions as an important food source for many vertebrates including snakes and predatory birds. As of now, the western fence lizard is listed as unprotected, and no conservation restrictions apply.
The habitat loss also causes a decrease in the number of scales. This is because of the urban heat island effect, increasing the temperature year round.
Behavior
These lizards are diurnal, and are commonly seen basking on paths, rocks, and fence posts, and other suitable sunny locations.