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Desert Horned Lizard
Phrynosoma platyrhinos
Family: Phrynosomatidae Order: Squamata Class: Reptilia
DISTRIBUTION, ABUNDANCE, AND SEASONALITY
The desert horned lizard is a common yearlong resident in the Mojave, Sonoran
and Colorado deserts (Behler and King 1979) as well as in the northeastern corner of
the state. An isolated population exists in San Jacinto River Wash, Riverside Co.
(Stebbins 1972). It occurs in all
desert shrub
types and grass/forb stages of
pine-juniper woodlands.
Sparse or open habitats are preferred by the desert horned lizard.
Its elevational range extends from below sea level to 2130 m (7000 ft) (Macey and
Papenfuss 1991). This species is most active from April to July in lower elevations
and from May to September in higher areas.
SPECIFIC HABITAT REQUIREMENTS
Feeding:
Feeds primarily on ants, also beetles and their larvae, and plant material
(Leviton 1972). Forages in rocky and sandy areas (Lawrence and Wilhoft 1958, Shaw
1950), generally sitting and waiting for prey (Pianka and Parker 1975).
Cover:
Sandy soil is preferred for burrowing but also found in sandy-gravelly drainage
channels
(desert wash) (Stebbins 1954).
Reproduction:
Eggs are laid in well-drained sandy soil.
Water:
Obtains water from food.
Pattern:
Found primarily on sandy and gravelly flats, often in areas of wind-blown sand
or along washes in arid and semiarid regions (Stebbins 1954).
SPECIES LIFE HISTORY
Activity Patterns:
Diurnal (Leviton 1972). Most active April to July at lower elevations,
May to September at higher elevations. Hibernates during cool season.
Seasonal Movements/Migration:
None.
Home Range:
18-22.5 m (59-74 ft) in diameter (Pianka and Parker 1975).
Territory:
Poorly developed (Tanner and Krogh 1973), but this species uses assertive
displays (Tollestrup 1981).
Reproduction:
Breeds May to June. Most eggs are laid in June and early July. Clutch
size 7-13 eggs (Taylor 1912).
Niche:
This species overlaps in range with the flat-tailed horned lizard. One record
of predation by prairie falcon (Stebbins 1954); probably eaten by
roadrunners
and
hawks.
Leopard lizards
and
snakes
may prey on this species, but antipredator displays are often
effective (Tollestrup 1981).
REFERENCES
Behler, J. L., and F. W. King. 1979. The Audubon Society field guide to North American Reptiles and amphibians. Alfred Knopf, New York. 743pp.
Lawrence, J., and D. Wilhoft. 1958. Cryptic coloration in lower-dwelling horned lizards. Copeia 1958: 43-44.
Leviton, A. E. 1972. Reptiles and amphibians of North America. Doubleday and Co., New York. 250pp.
Macey, J. R. and T. J. Papenfuss. 1991. Reptiles. Pages 291-360 in C.A. Hall, Jr., editor. Natural History of the White-Inyo Range eastern California. Univ. Calif. Press, Berkeley, California. 536 pp.
Pianka, E. R., and W. S. Parker. 1975. Ecology of horned lizards: a review with special reference to Phrynosoma platyrhinos. Copeia 1975:141-162.
Shaw, C. E. 1950. The lizards of San Diego County with descriptions and key. Bull. Zool. Soc. San Diego 25:1-100.
Stebbins, R. C. 1954. Amphibians and reptiles of western North America. McGraw-Hill, New York. 536pp.
Stebbins, R. C. 1972. California amphibians and reptiles. Univ. California Press, Berkeley. 152pp. Tanner. W. W., and J. E. Krogh. 1973. Ecology of Phrynosoma platyrhinos at the Nevada Test Site, Nye County, Nevada. Herpetologica 29:327-342.
Taylor, W. P. 1912. Field notes on amphibians, reptiles, and birds of northern Humboldt County, Nevada, with a discussion of the faunal features of the region. Univ. Calif. Publ. Zool. 7:319-436.
Tollestrup, K. 1981. The social behavior and displays of two species of horned lizards, Phrynosoma platyrhinos and Phrynosoma coronatum. Herpetologica 37:130-141.
California Department of Fish and Game. California Interagency Wildlife Task Group. 2005. California Wildlife Habitat Relationships version 8.1 personal computer program. Sacramento, California.
Phrynosoma coronatum, Coast Horned Lizard - Dick Schwenkmeyer and Brad Hollingsworth. San Diego Natural History Museum
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:
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.
Special Note:
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.
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.
