FWS Focus


Scientific Name

Thamnophis sirtalis tetrataenia
Common Name
San Francisco Garter Snake
San Francisco Gartersnake
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The San Francisco garter snake’s historical range extended from the San Francisco-San Mateo County line south along the base of the Santa Cruz Mountains into northern Santa Cruz County.

Recent surveys suggest that there has been very little decrease in the overall extent of the San Francisco garter snake range compared to its historical distribution; however, there are fewer populations and overall numbers of snakes within that range, and some sites have been extirpated. Remaining populations have been fragmented due to urbanization. Today, the snake is found in isolated populations, mostly along the coast in San Mateo County. 

The San Francisco garter snake requires both aquatic and upland habitat. They are often found in or next to aquatic freshwater habitat, including ponds, creeks, marshes, canals and other water sources, which they use for foraging and basking during the day. They also use grassy areas near water sources to regulate their body temperature, find cover, forage, mate and hibernate. During colder months, the snake moves into underground rodent burrows or under rocks for shelter.  


Land on which the natural dominant plant forms are grasses and forbs.


A considerable inland body of standing water.


The land near a shore.

River or Stream

A natural body of running water.


Areas such as marshes or swamps that are covered often intermittently with shallow water or have soil saturated with moisture.

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Life Cycle

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Physical Characteristics


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