San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
Coast Horned Lizard, photo by Jim Melli

Phrynosoma coronatum
Coast Horned Lizard

PHRYNOSOMATIDAE

Phrynosoma is derived from Greek -- phrynos, meaning "toad," and soma, meaning "body." Coronatus is Latin for "crowned."

Description

The Coast Horned Lizard is relatively large and less rounded than other horned lizards. An individual's snout-vent length can reach 4 inches. Numerous pointed scales stick out along the sides of the body and over the back, though only the horns around the head are rigid.

The back pattern begins with two large, dark blotches behind the head, followed by three broad bands on the body and several smaller bands on the tail. The general coloration consists of various shades of brown with cream colored accents around the blotches and the outer fringe of scales.

Subspecies: There have been as many as six subspecies recognized: the San Diego Horned Lizard (P. c. blainvillii); the Cape Horned Lizard (P. c. coronatum); the California Horned Lizard (P. c. frontale); the Central Peninsular Horned Lizard (P. c. jamesi); the Northern Peninsular Horned Lizard (P. c. schmidti); and the Cedros Island Horned Lizard (P. c. cerroense). All intergrade widely and the recent studies indicate that no subspecies should be recognized.

Range and Habitat

The Coast Horned Lizard's range extends from northern California to the tip of Baja California. The subspecies found in southern California, blainvillii, is distributed throughout the foothills and coastal plains from Los Angeles area to northern Baja California. It frequents areas with abundant, open vegetation such as chaparral or coastal sage scrub. A ground dweller, it's never seen climbing into shrubs or trees, or onto the sides of large boulders.

Natural History

When threatened by animals like the coyote, the Coast Horned Lizard can shoot a small stream of blood from its eyes. This is how it happens: the horned lizard increases the blood pressure in its head; when the pressure increases, tiny blood vessels in the corner of eyes rupture and blood shoots out, sometimes as far as four feet. This provides a moment of distraction and allows the lizard to get away.

Perhaps the horned lizard's best defense mechanism is its disruptive or cryptic coloration, which is so similar to their background they become indistinguishable from it. This is partly due to its ability to change its own color to match its background environment. Its flat profile helps prevent shadows that might be detected by an observant predator, such as a hawk flying overhead or a coyote patrolling the ground. Most predators would have difficulty grabbing these lizards because of their horns. They are known to swivel their head back in attempts to stab the hand which grasps.

Ants are the favorite food of horned lizards, making up about 50% of their diet. The lizards also eat honeybees and a variety of other insects.

The Coast Horned Lizard produces clutches of 6 to 21 eggs from May to June. Hatching occurs in August and September.

Conservation Status

The Coast Horned lizard is currently a Federal Special Concern species (FSC) and a California Special Concern species (DFG-CSC). California Depatment of Fish and Game gives them full protection from collecting.

A number of factors contribute to the decline of this species. The subspecies blainvillii is believed to be extinct in 45% of its original range in southern California. The most serious threat is the destruction of its preferred habitat along the coast. Populations in undisturbed areas seem to fare quite well, although the introduction of Argentine Ants (Iridomyrmex humilis) are now replacing the native ant food base. It was heavily exploited at the turn of the century for the curio trade; horned Lizards were varnished and sold to visiting tourists from the east coast, or simply sold as pets to take home as a souvenir. Later, biological supply companies and the modern pet trade contributed to their exploitation, until 1981, when commercial collecting was banned.


Text by Dick Schwenkmeyer and Brad Hollingsworth.
Photo of juvenile Horned Lizard by Jim Melli

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