General Distribution
Wide-ranging and locally very abundant, the common garter snake is absent only from
Alpine Co. southward (east of the Sierra crest), the southern desert regions, and coastally
from northern San Diego Co. south to the Mexican border. Associated with permanent or
semi-permanent bodies of water in a variety of habitats. Elevation sea level to 2400 m (8000
ft). The Endangered San Francisco garter snake (T. s. tetrataenia) is extremely scarce and
occurs only in the vicinity of ponds and reservoirs in San Mateo Co. (Barry 1975). Habitat Requirements
The preferred nocturnal retreats of this active diurnal snake are thought to be
holes, especially small mammal burrows, crevices, and surface objects. During the day
common garter snakes often bask in the open near shelter (Stewart 1965). In cold areas,
garter snakes often winter, aggegated, sometimes with other species, in fissures in rocky
accumulations or in mammal burrows. In milder areas mammal burrows and surface objects
such as flat rocks and rotting logs serve as winter refuges. Reproduction
Courtship and mating normally occur in early spring soon after emergence
from hibernation. During the mating season several males often attempt to
mate with a single female (Gardner 1957, Aleksiuk and Gregory 1974). Three to 20 live
young (larger litters have been reported) are born from July to August. Daily/Seasonal Activity
An active diurnal snake. During the warm days of summer most activity
occurs during morning and late afternoon. During the cooler weather of spring and fall, and at
higher elevations, snakes restrict ther activity to the warm afternoons. On warm days during
winter garter snakes have been observed to emerge and bask in the sun at the entrances of
hibernacula. Diet and Foraging
The common garter snake forages on land or in quiet pools, generally avoiding
swift water. Studying this species in the Sierra Nevada, White and Kolb (1974) found that
they consumed treefrogs, fish, mice, leeches, earthworms, and toads in order of importance.
A wide variety of vertebrate prey including small mammals, birds, lizards, and amphibians
have been reported as among the food items commonly taken. Fitch (1941) listed slugs,
earthworms and leeches as the favorite invertebrate prey. Territoriality/Home Range
The nature of the home range of garter snakes in California is not well
known. There is likely considerable overlap in the home ranges of garter snakes during the
period of summer activity. Individuals can be located every few meters along the suitable
shorelines. Nussbaum et al. (1983) report finding over 150 common garter snakes in an hour
of searching along the Willamette River in Oregon. Not thought to be territorial, common garter snakes often remain aggregated in
large numbers from fall through early spring. Predator-Prey Relations
Common garter snakes are taken as prey by mammals, birds and other snakes
despite the release of a repulsive musk from the postanal glands of disturbed individuals. Literature Cited
Aleksiuk, M. 1977. Cold-induced aggregative behavior in the red-sided garter snake
(Thamnophis sirtalis parietalis). Herpetologica 33:98-101.
Aleksiuk, M., and P. T. Gregory. 1974. Regulation of seasonal mating behavior in
Thamnophis sirtalis parietalis. Copeia 1974:681-689.
Barry, S. J. 1975. Status of the San Francisco garter snake. Calif. Dept. Fish and Game,
Inland Fish. Endangered Species Program Special Publ. 78-2. 21pp.
Fitch, H. S. 1941. The feeding habits of California garter snakes. Calif. Dept. Fish and
Game 27:1-32.
Fitch, H. S. 1980. Thamnophis sirtalis. Cat. Amer. Amphibians and Reptiles 270.
Gardner, J. B. 1957. A garter snake "ball". Copeia 1957:48.
Nussbaum, R. A., E. D. Brodie, Jr., and R. M. Storm. 1983. Amphibians and reptiles of the
Pacific Northwest. Univ. Press of Idaho. 332pp.
Stewart, G. R. 1965. Thermal ecology of thegarter snakes Thamnophis sirtalis conncinus
(Hallowell) and Thamnophis ordinoides (Baird and Girard. Herpetologica 21:81-102.
White, M., and J. A. Kolb. 1974. A preliminary study of Thamnophis near Sagehen Creek,
California. Copeia 1974:126-136.
Information gathered from California DFG - California Interagency Wildlife Task Group
