General Distribution
The coast horned lizard is uncommon to common in suitable habitat. Occurs in
valley-foothill hardwood, conifer and riparian habitats, as well as in pine-cypress, juniper and
annual grass habitats. Ranges in the Central Valley from southern Tehama Co. south; in the
Sierra foothills from Butte Co. to Tulare Co. below 1200 m (4000 ft); below 1800 m (6000 ft) in
the mountains of southern California exclusive of desert regions; throughout the Coast
Ranges south from Sonoma Co. There is an isolated population in Siskiyou Co. Habitat Requirements
This species relies on camouflage for protection and often hesitates to move at the
approach of a predator. Horned lizards often bask in the early morning on the ground or on
elevated objects such as low boulders or rocks. Predators and extreme heat are avoided by
horned lizards by burrowing into loose soil. Periods of inactivity and winter hibernation are
spent burrowed into the soil under surface objects such as logs or rocks, in mammal burrows,
or in crevices. Reproduction
The reproductive season for the coast horned lizard varies from year to
year and geographically depending on local conditions. Pianka and Parker (1975) reported
that egg-laying in southern California extends from late May through June with a mean clutch
size of 13 eggs. Stebbins (1954) reported a range of 6 to 16 eggs. Hatching probably occurs
after two months. The coast horned lizard is apparently unique among lizards in using a
belly-to-belly position during copulation (Tollestrup 1981). Daily/Seasonal Activity
Being a diurnal lizard, most activity occurs during the middle of the day
in the spring and fall but is restricted to morning and late afternoon during mid-summer.
Nocturnal activity may occur during particularly warm periods. Fall and winter are inactive
periods in most areas. Pronounced seasonal movement or migration has not
been reported. Habitat requirements, such as sites for courtship and display, egg-laying, and
hibernation are apparently found within the normal area of activity. Diet and Foraging
Horned lizards forage on the ground in open areas, usually between shrubs and
often near ant nests. Pianka and Parker (1975) noted that this species, like other horned
lizards, consumes many ants. Small beetles are taken in large numbers when especially
abundant. Stebbins (1954) reported other insects as food items, including wasps,
grasshoppers, flies, and caterpillars. Territoriality/Home Range
Little is known about home range. In Arizona, some individuals of a related
horned lizard species, P. solare, established well-defined home ranges, while some wandered
without establishing one. Males used a larger area than females; the mean maximum
distance between capture points was 30 m (98 ft) for males and 15 m (49 ft) for females
(Baharav 1975). Horned lizards generally lack territorial defense (Lynn 1965, Stamps 1977), but
combat between males (Whifford and Whifford 1973) and over female feeding territories
(Nussbaum et al. 1983) has been reported. Predator-Prey Relations
The spiny armour and aggressive behavior towards potential predators exhibited
by horned lizards confer only partial immunity from predators. Leopard lizards, sidewinders,
striped whipsnakes and other snakes, loggerhead shrikes, and hawks have all been reported
as predators of horned lizards. Literature Cited
Baharav, D. 1975. Movement of the horned lizard Phrynosoma solare. Copeia 1975:
649-657.
Lynn, R. T. 1965. A comparative study of display behavior in Phyrnosoma (Iguanidae).
Southwest. Nat. 10:25-30.
Nussbaum, R. A., E. D. Brodie, Jr., and R. M. Storm. 1983. Amphibians and reptiles of
the Pacific Northwest. Univ. Press of Idaho. 332pp.
Pianka, E. R., and W. S. Parker. 1975. Ecology of horned lizards: a review with special
reference to Phrynosoma platyrhinos. Copeia 1975:141-162.
Stamps, J. A. 1977. Social behavior and spacing patterns in lizards. Pages 265-334 in
C. Gans and D. W. Tinkle, eds. Biology of the Reptilia. Vol. 7. Academic Press, London.
Stebbins, R. C. 1954. Amphibians and reptiles of western North America. McGraw-Hill,
New York. 536pp.
Tollestrup, K. 1981. The social behavior and displays of two species of horned lizards,
Phrynosoma platyrhinos and Phrynosoma coronatum. Herpetologica 37:130-141.
Whitford, W. B., and W. G. Whitford. 1973. Combat in the horned lizard Phrynosoma
coronatum. Herpetologica 29:191-193.
Information gathered from California DFG - California Interagency Wildlife Task Group
