Sunday, January 9, 2011

Side-blotched Lizards in Palm Springs

Chilly-day lizard integral in chain
The Desert Sun, Palm Springs, California
January, 9, 2011
James Cornett
The following is unedited.
Side-blotched Lizards, NPS

There is just one species of reptile that can be seen in the valley in January, the coldest month of the year. Known as the side-blotched lizard because of a dark spot on each side, this is the only lizard that is out and about on cold winter days.

Its small size (just under 2 1/2 inches excluding the tail), allows it to heat up rapidly providing there is no wind. As the morning progresses and the lizard reaches its preferred body temperature of 99 degrees, it becomes lighter in color, which then helps reflect excess radiation and prevent overheating. Color change, altering posture in relation to the angle of the sun’s rays and movements in and out of shade help the side-blotched lizard maintain a fairly constant body temperature, nearly identical to that of humans.

Once warm, a side-blotched lizard can move quickly in order to catch fast-moving insects such as grasshoppers and moths. In addition to these insects, it also consumes large numbers of beetles, moth larvae and ants. In one case, an individual was observed to eat 50 ants in a two-hour period. Ants appear to be the staple food of juvenile side-blotched lizards, as well.

Because of their willingness to consume ants when no other insects are available, side-blotched lizards are an important — perhaps critical — link in several desert food chains. Most harvester ant colonies survive extended drought because they consume and store seeds, a food resource that persists year after year. Because side-blotched lizards eat ants, they, too, survive prolonged drought. The side-blotched lizard's survival enables at least some lizard-eating predators (such as roadrunners, collared lizards, night snakes) to survive as well, completing the food chain.

A male establishes a relatively large territory during spring, and attacks other males that enter its domain. The male bobs up and down, and puffs up its torso. If this is unsuccessful, an attack is likely.

Side-blotched lizards are the first reptiles to breed in spring and are known to breed throughout the year in our southern deserts. Up to six clutches of eggs are laid per year. Sperm may be stored in the female's oviduct for several months, enabling her to lay more than one fertile clutch without mating a second time. A typical clutch consists of from two to six eggs. The high rate of reproduction is largely responsible for this species being the desert's most abundant and widespread reptile.

James Cornett is a desert ecologist living in Palm Springs.

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