f/EPA
The San Francisco garter snake
is an endangered species.
Endangered species are
plants and animals that are
in immediate danger of
becoming extinct.
Threatened species are plants
and animals whose population
numbers are so low that they
may become endangered in the
future.
The U.S. Environmental
Protection Agency's (EPA)
Endangered Species Protection
Program (ESPP) will help
ensure that pesticide use does
not jeopardize the survival of
listed species.
San Francisco Garter Snake
Description and Ecology
Status Endangered, listed March 11, 1967.
Critical Habitat Not designated.
Appearance The elusive, San Francisco garter snake is
frequently described as one of North America's most beautiful
snakes. Running down the center of its back is a wide,
greenish-yellow stripe edged on each side by black bands.
These black bands, in turn, are edged by red bands. Here the
juncture between the black and red may be less distinct, and
sometimes the red band is broken or divided. Yet another
parallel black band edges the red band further down on each
side. All bands run parallel the length of the body, except for
on the head; the top of the head is fully red. The lower head
and belly are greenish-blue or turquoise blue. The eyes are
large. The length of this slender, beautiful snake which is not
a threat to humans, may extend to 51 inches.
Range The historic range of the San Francisco garter
snake was largely restricted to the San Francisco Peninsula,
stretching south from near the San Francisco-San Mateo
County border along the eastern and western base of the
Santa Cruz Mountains. Populations may have occupied the
Buri Buri Ridge along the San Andreas Rift ana then locations
south in an arc from the San Gregorio-Pescadero Highlands
west to Tunitas Creek. Populations likely extended south from
there along the western coast of the Peninsula to what is now
Ano Nuevo State Reserve. While recent surveys indicate that
the overall range of the San Francisco garter snake has not
diminished, some local populations within that range have
been extirpated and others seem to be declining.
Habitat The preferred habitats of San Francisco garter
snakes are densely vegetated ponds near open hillsides.
Because San Francisco garter snakes can only hunt in water
that is 2 inches deep or less, aquatic habitats with shallow
water edges are essential. In the spring and early summer,
during their first peak of activity, San Francisco garter snakes
are often found around ephemeral ponds hunting Pacific
TmiMMMphk UrtaMs tetrtxtumJji
tree frogs. Pacific tree frogs utilize ephemeral ponds for
reproduction to avoid the usual predators found in permanent
ponds.
As ephemeral ponds dry and Pacific tree frogs (metamorphs
following the adults) retreat to wooded areas, San Francisco
garter snakes shift to more permanent aquatic habitats.
California red-legged frogs reproduce later in the season and
select aquatic habitat that will not dry up before the young
of the year metamorphose in July and August. These become
the next important food source for the San Francisco garter
snake and stimulate a second peak of activity. Dispersing
frogs may encourage snake dispersal along riparian corridors.
San Francisco garter snakes also prey upon California
newts, western toads, mosquito fish and, on occasion, small
mammals.
San Francisco garter snakes also require upland habitat:
south or west facing slopes with suitable sites for basking,
and rodent burrows or thick mats of grass for shelter and
hibernacuia. Optimal hillside vegetation is thought to be a
grassland/shrub matrix with a density of one shrub for every
20-30 square feet. This provides both protective cover and
exposed surfaces for thermoregulation.
Reproduction and Life Cycle Although mating
can occur in the fall, the first warm days of March encourage
encounters as San Francisco garter snakes emerge from their
hibernacuia and concentrate in nearby aquatic habitat. Like
other garter snakes they are ovoviviparous, that is, following
fertilization the female retains the eggs inside her body until
hatching occurs so that in July and August offspring are born
live, and independent. There may be 12-24 in a litter.
Bullfrogs prey upon young San Francisco garter snakes and
further impact garter snake populations by preying upon
California red-legged frogs.
ThMMicfkis tirtiuUs tefrottmwi
Office of Pesticide Programs (7507P)
http://www.epa.gov/espp/
February 2010

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SdUl FrMld
Recovery Plan The U.S. Fish and Wildlife Service (FWS)
developed a recovery plan for the San Francisco garter snake
in 1985. Recovery plans outline reasonable actions that FWS
believes are required to recover or protect listed species.
FWS prepares recovery plans, sometimes with the assistance
of recovery teams, contractors, state agencies, and others.
Recovery plans do not necessarily represent the views nor the
official positions or approvals of any individuals or agencies,
other than FWS, involved in the plan formulation. Approved
recovery plans are subject to modification as dictated by new
findings, changes in species' status, and the completion of
recovery tasks.
Sari Francisco Garter Snake
Information Sources
Primary Reference Beacham, Walton, Castronova,
Frank F., and Sessine, Suzanne (eds.) 2001. Beacham's Guide
to the Endangered Species of North America, Gale Group,
New York. Vol. 1, pp. 672-674.
Listing Notice U.S. Fish and Wildlife Service,
1967. Federal Register 32:4001, March 1967.
http://ecos.fws.gov/docs/federal_register/frl8.pdf
Recovery Plan U.S. Fish and Wildlife Service,
1985. Recovery Plan for the San Francisco Garter
Snake, Thamnophis sirtalis tetrataenia. U.S. Fish and
Wildlife Service, Region 1, Portland, Oregon. 77 pp.
http://ecos.fws.gov/docs/recovery_plan/850911.pdf
Species Account u.s. Fish ana
Wildlife Service, Sacramento Field Office.
http://www.fws.gov/sacramento/es/animal_spp_acct/sf_
garter_snake.pdf
Pacific treejrotjj '{trey species -for San Francisco garter snake /
Mike BettoM), FWS Trinity River H-erjzetvpiuna. Research
v>EPA
AdiUt San Francisco garter snake., San KAateo Couwty
©Gary Najis, wmv.c^Ujvrnuik^rrps.c&m
Underside oj- adult San Francisco garter snake
©Gary Najuj wuw.cati^nAakerpt.c&m

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