The Western Fence Lizard (Sceloporus occidentalis) is a common lizard of California and surrounding areas. It is also known as the Blue-belly.
It is a member of the genus Sceloporus, and therefore is a spiny lizard.
Subspecies occidentalis courting on a log
Western fence lizards are about 8-10 cm long excluding their tail, and about 15 cm long with the tail included. They are brown to black in color (the brown may be sandy or greenish), but adult males have iridescent blue lateral patches on their flanks, and their entire bodies may be flecked with blue. Males may expose their blue stomachs in a territorial display. The blue is much less pronounced in females.
The western fence lizard eats insects and spiders. They are commonly seen sunning on paths and rocks, and this behavior makes them vulnerable to predation by snakes and birds.
Although California is the heart of the range of this lizard, it is also found in eastern and southwest Oregon, as well as in the Columbia River Gorge, southwest Idaho, Nevada, western Utah, and northwestern Baja California, and some of the islands off the coast of both California and Baja California. It is found in scrub and chaparral, up to elevations approaching 2000 meters, but it is not generally found in the desert.
Rarely, this species can be found living on Joshua trees (Yucca brevifolia) that exist along the northern slope of the San Gabriel Mountains. These populations are dominated by a striped phenotype which is otherwise quite rare.
They are commonly seen sunning on paths and rocks, and this behavior makes them vulnerable to predation by snakes and birds.
The taxonomy of this species is currently under discussion: until recently, six subspecies were recognized, as follows:
- Island fence lizard, Sceloporus occidentalis becki
- 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. However, recent work in molecular systematics has suggested that there are four clades and 11 genetically separable populations, and the subspecies will probably have to be redefined.
Closeup of head
It is thought that the presence of western fence lizards diminishes the danger of transmission of Lyme disease by ticks. The incidence of Lyme disease is lower in areas where the lizards occur, and it has been found that when ticks carrying Lyme disease feed on these lizards (which they commonly do, especially around their ears), the bacteria that cause the disease are killed.