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Western Fence Lizard

Western Fence Lizards wrestle for possession of juicy caterpillar.

Western Fence Lizards wrestle over rights to a juicy caterpillar. The bright blue belly and yellow underarms of the lower lizard indicate he is male. The upper lizard, with turquoise markings on its back, may also be male.
© 2014 Talila Golan

Scientific name: Sceloporus occidentalis. The genus name Sceloporus comes the Greek word skelos, meaning “pores” and “legs”, referring to the small pores (microscopic holes) on the undersides of these lizards’ legs. The species name occidentalis is a reference to their range location in the west.

Appearance and size: Western Fence Lizards come in colors from tan to black or brown, and have longitudinal grey stripes on their backs, with light tan stripes in a horizontal wave pattern. The most well known feature is their blue throats and abdominal undersides, which give this lizard the nickname “blue belly”. The lower sides of the arms and legs are yellow, but not as prominent as the blue abdomens. Only adult males have these bright colorations; those in females and juveniles are dull. This makes gender easy to determine. Western Fence Lizards have sharply pointed scales, which is why they are considered part of the “spiny lizards” family. These lizards usually grow up to 4.5 – 6.0 inches from the snout to the tip of the tail. The fingers and toes have sharp claws for climbing.

Habitat: Found in coniferous forests, oak woodland chaparral, and grassland. They are rare in deserts.

Range: Throughout the states of California, Oregon, and Washington, as far east as Nevada and southwestern Idaho.

Diet: They eat insects and spiders.

Predators: Predators include snakes, coyotes, bobcats, and hawks. The lizard’s tail can be detached as a mechanism to escape, and it is eventually regrown.

Possibly pregnant female Western Fence Lizard (Sceloporus occidentalis).

Possibly pregnant female Western Fence Lizard.
© 2014 Matthew James

Life cycle: Western Fence Lizards mate from April to July. Females go through a gestation period of 3-6 weeks, in which the sides of their abdominal region widen. They lay up to three clutches of 10 to 17 eggs throughout late spring and early summer. The eggs hatch in July to August, which is the time when tiny (1-2 inch) juvenile lizards are most common. Young lizards do not breed until the spring of their second year. Their average lifespan in the wild is 5-7 years.

Western Fence Lizards at Edgewood

  1. Where at Edgewood am I likely to see or hear Western Fence Lizards? The lizards are very common and easily observed sitting on rocks, logs, and climbing up fence posts. They are most frequently heard rustling in the plants next to the trails.
  2. How is the males’ blue underside significant in their behaviors? Female Western Fence Lizards tend to prefer the males with the longest tails and brightest color patterns. Males often do a pushup-like motion on logs and rocks to display their colorful undersides as a warning to other males to stay away from the females. This is a common territorial behavior that male Western Fence Lizards engage in during the mating season.
  3. What times of day and year can I see and hear them? Western Fence Lizards are strictly diurnal. The adults are most easily observed in late spring and early summer, while the small juveniles are most common from late July to October. They are easy to hear running around in shrubs and grass. When humans get close, the lizards will quickly run for the nearest shelter, such as in nearby plants or complexes of rocks or sticks. They sometimes climb up trees or fences to escape, which is how they get the name of “Western Fence Lizard”.
  4. What do they do in the cold season? In the winter months, Western Fence Lizards enter a period of hibernation. They take shelter under wooden boards or in rock crevices from late November until the mating season starts.
  5. Western Fence Lizard (Sceloporus occidentalis) missing its tail feeding on termites.

    Stumpy-tailed Western Fence Lizard feeds on termites. The tail will regrow.
    ©  2005 Alf J. Fengler

    How do Western Fence Lizards lose their tails and when do they grow back? Western Fence Lizards can detach or drop their tails to escape from predators if the tail is grabbed. The tail usually regrows in 3-5 weeks. The new tail is never identical to the original, as it is almost always shorter and has a different pattern of tiny scales.

  6. Is it true that these lizards are immune to  Lyme disease? Western Fence Lizards have been found to have immunity to Lyme disease. When ticks with the disease feed on these lizards’ blood, a protein in the lizards’ blood kills the bacteria that causes the disease. The blood in the ticks’ gut is also cleansed of the disease as a result. This prevents the ticks from spreading Lyme disease when they bite other animals.
  7. Where can I learn more?
    Family Phrynosomatidae on Animal Diversity Web
    Small Spiny Lizards in California on California Herps
    Life history account for Western Fence Lizard
    Feeding on lizard blood strips ticks of dangerous Lyme disease bacterium
    Hard Science on Lyme
    Fence Lizards in Love

Information compiled by Matthew James 2014