EnMuujered Species facts
&EPA
Pkoio source: B. Moose Peterson,
The salt marsh harvest mouse
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.
Salt Marsh Harvest House Zedthro^ontmws ramrnnirk
Description and Ecology
Status Endangered, listed October 13, 1970.
Critical Habitat Not Designated.
Appearance The salt rnarsh harvest mouse is thought to
have evolved from the more common western harvest mouse,
which it resembles. Its small, 2.75-3 inch-long body is buff
to brown, darker than that of the western harvest mouse, as
are its ears. It may also have a dark stripe down its back. Of
the two subspecies, the northern Reithrodontomys raviventris
halicoetes has a white belly. The southern R. r. raviventris has
a cinnamon-colored belly, which is the origin of a common
name for the species, "red-bellied harvest mouse."
Range Once the salt marsh harvest mouse ranged along
the central coast of California. It was concentrated, as it
still is, in the salt marshes of the San Francisco Bay area.
However, today the mouse's populations are smaller and
isolated from each other, largely due to human activities. The
northern subspecies inhabits marshes around San Pablo Bay
and up the Petaluma River to the Petaluma Marsh, marshes
around Suisun Bay east to the Delta of the San Joaquin and
Sacramento River, and still other marshes, including some
south on the Marin Peninsula. This area includes lands in
the San Pablo Bay National Wildlife Refuge (NWR) and lands
protected and managed under the Suisun Marsh Preservation
Agreement. Suisun Marsh is the largest contiguous brackish
water marsh remaining on the West Coast. The southern
subspecies is found in the marshes around the southern and
southeastern shore of San Francisco Bay. This includes land in
the San Francisco Bay NWR.
Habitat Salt marshes are the optimal habitat for this
species, in particular those that support dense stands
of pickleweed and are adjacent to upland, salt-tolerant
vegetation, for escape during high tides. The ability to
tolerate high salinity in both food (grasses, forbs, seeds, and
insects) and water, and the ability to swim and climb enable
this mouse to take advantage of its unique habitat. However,
the once extensive marshes of San Francisco, San Pablo and
Suisun Bays are now extremely fragmented. Of the 193,800
acres of tidal marsh existing in the 1850s, only about 30,100
remain. Some of the marshes have been pared to remnants
that are totally flooded by high tides, leaving no nigh-ground
retreat in which the salt marsh harvest mouse might take
refuge. Any rise in sea level combined with a reduction of
sediment deposition resulting from upstream dams and water
diversions would contribute to the loss of more salt marsh
habitat.
Reproduction and Life Cycle The life span of the
salt marsh harvest mouse is about 8 to 12 months. This
requires that the population renew itself every year in order
to survive. While sexually active from March to November,
females often bear only one of the three possible litters, and
litters of only four offspring are typical. If there is a nest, it is
only a loose ball of grasses on the surface of the ground. The
salt marsh harvest mouse does not burrow. It is vulnerable to
snakes, owls, hawks, and cats.
Young salt marsh harvest mice can disperse a considerable
distance, but not from fragmented habitat across bare or
converted environs.
Recovery Plan The U.S. Fish and Wildlife Service (FWS)
developed a recovery plan for the salt marsh harvest mouse
in 1984. Recovery plans outline reasonable actions that the
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 the 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.
Rnduo^ofvtmiys roummvtrk
Office of Pesticide Programs (7507P)
http://www.epa.gov/espp/
February 2010

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Salt Marsh
Salt Marsh Harvest Mouse Information
Sources
Primary Reference Beacham, Walton,
Castronova, Frank F., and Sessine, Suzanne (eds.)
Beach arm's Guide to the Endangered Species of North
America, Gale Group, New York. Vol. II, pp.1348-1350.
Listing Notice U.S. Fish and Wildlife Service,
1970. Federal Register 35, No. 199, pp. 16047-16048.
http://ecos.fws.gov/docs/federal_register/fr27.pdf
Recovery Plan U.S. Fish and Wildlife Service, 1984.
Salt Marsh Harvest Mouse and California Clapper Rail Re-
covery Plan. U.S. Fish and Wildlife Service, Pacific Region,
Portland, Oregon. 141 pp.
http://ecos.fws.gov/docs/recovery_plan/841116.pdf
Species Account u.s. Fish and wildlife
Service, Sacramento Fish and Wildlife Office, 2008.
http://www.fws.gov/sacramento/es/animal_spp_acct/
salt_marsh_harvest_mouse.pdf
Mouse
San Francisco Bay wtUwAs, Don. Edwards NWK.
Jakft and Karen Hi^Umgswortk/USfWS Digital Library
Pick^&wttd courtesy oj- Stem MatsOK
Salt masrsk harvest mouse reieAA^/Calijorwui Department o^ Water Resources
	SEPA

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