Articles on this page are available in 1 other language: Spanish (3) (learn more)

Overview

Brief Summary

Description

"Salt marsh Harvest Mice have a very limited range—they live only in San Francisco Bay's tidal marshes and diked salt marshes—and they have very specific habitat requirements. They need dense cover. They are good swimmers, but if they are forced into the open they are picked off by predators such as owls, skunks, cats, rats, and foxes. They also need somewhere to go when the water rises at high tide. The Mice depend on pickleweed and other plants that grow in the salty soil of the marshes for both cover and safe places to climb above water level. Much of their habitat has been lost to development, and in some places, flow from sewage plants has changed the water quality, affecting which plants can grow. Although the Mice can have two or three litters a year, their survival in the wild is in question."

Links:
Mammal Species of the World
Click here for The American Society of Mammalogists species account
  • Original description: Dixon, J., 1908.  A new harvest mouse from the salt marshes of San Francisco Bay, California, p. 197.  Proceedings of the Biological Society of Washington, 21:197-198.
Creative Commons Attribution 3.0 (CC BY 3.0)

© Smithsonian Institution

Source: Smithsonian's North American Mammals

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Distribution

Salt-marsh harvest mice (Reithrodontomys raviventris), are limited to saltwater and brackish marshes bordering the San Francisco Bay area. Because these marshes have been altered by humans, throught draining, diking, and similar opperations, the distribution of this species is disjunct. The large Petaluma Marsh (in Sonoma County) supports a considerable amount of salt marsh harvest mice. The species is distributed eastward through Suisun Bay to the opening of the Sacramento River at Antioch Dunies. It reaches western regions through the marshes at the opening of Callinas Creek on the upper Marin Peninsula, and as far south to the San Mateo Bridge; including marshes in the San Francisco Bay National Wildlife Refuge.

Biogeographic Regions: nearctic (Native )

  • Castronova, V., W. Beachman. 1994. Beachmans's guide to the endangered species of North America. Farmington Hills, MI: Beachman Publishing Inc..
  • Shellhammer, H. 1982. Reithrodontomys raviventris. Mammalian Species, 169: 1-3.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Range Description

This species is restricted to habitats bordering San Francisco Bay in California in the United States. Occurrence within this small range is highly fragmented. The range encompasses salt marshes of the San Francisco Bay system (San Francisco, San Pablo, and Suisun bays), in central California (Shellhammer 1982). Subspecies halicoetes occurs in marshes of San Pablo and Suisun bays (and including Petaluma Marsh in Sonoma County) and along the northern Contra Costa County coast (east to Antioch dunes area), and subspecies raviventris occurs mostly in the southern part of South San Francisco Bay, with a few populations on the Marin Peninsula (west to the mouth of Gallinas Creek) and near Point Richmond (Shellhammer 1989). The remaining tidal marsh habitat in the San Francisco Bay Area is estimated to be 12,555 ha (=125 sq km). An unknown fraction of this habitat is actually occupied by this species.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

endemic to a single state or province

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Global Range: (<100-250 square km (less than about 40-100 square miles)) The range encompasses salt marshes of the San Franciso Bay system (San Francisco, San Pablo, and Suisun bays), in central California (Shellhammer 1982).

Subspecies halicoetes: marshes of San Pablo and Suisun bays (and including Petaluma Marsh in Sonoma County) and along the northern Contra Costa County coast (east to Antioch dunes area).

Subspecies raviventris: mostly in southern part of South San Francisco Bay, with a few populations on the Marin Peninsula (west to mouth of Gallinas Creek) and near Point Richmond (Shellhammer 1989).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Historic Range:
U.S.A. (CA)

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Physical Description

Morphology

R. raviventris has a dark brown dorsal area with a dark stripe extending vertically on its back, and pinkish cinnamon or tawny on its ventral side. There are often tufts of yellowish hairs near the anterior base of the ears. The ears themselves are dark in color. The tail is indistingly bicolored, with brownish hairs on the surface. Salt marsh harvest mice from the Southern San Francisco Bay area usually have a red belly. Toward the north, many members of the species have a white belly.

R. raviventris has a total length ranging from 118 to 175 mm. Tail length is reported at between 56 and 95 mm. The hindfoot length is 15 to 21 mm. These animals can weight between 7.6 and 14.5 g.

Range mass: 7.6 to 14.5 g.

Average mass: 11.01 g.

Range length: 118 to 175 mm.

Other Physical Features: endothermic ; bilateral symmetry

  • Ruff, S., E. Wilson. 1999. The Smithsonian Book of North America. Washighton: Smithsonian Institution Press.
  • Whitaker, O. October 1998. Field Guide To Mammals. New York: Alfred A. Knopf.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Size

Length: 16 cm

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Size in North America

Length:
Range: 118-175 mm

Weight:
Range: 7.6-14.5 g
Creative Commons Attribution 3.0 (CC BY 3.0)

© Smithsonian Institution

Source: Smithsonian's North American Mammals

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Diagnostic Description

Differs from geographically adjacent subspecies of R. MEGALOTIS in having a thicker tail (2.1-3.0 mm vs. 1.9-2.0 mm, at 20 mm from body), an indistinctly bicolored tail (there are always brownish hairs on the under surface), longer and thicker pelage at all seasons, and a significantly longer braincase (Fisler 1965, Shellhammer 1982).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Ecology

Habitat

Salt-marsh harvest mice inhabit saline or brackish marshes. This species requires dense ground cover. R. raviventris prefers the cover of pickle weed, provided that it has non--submerged, salt-tolerant vegetation for escape during high tides. These mice rarely venture into the open.

Habitat Regions: temperate ; terrestrial

Wetlands: marsh

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Habitat and Ecology

Habitat and Ecology
The species' habitat consists of salt and brackish marshes, where plants provide a dense mat of cover, ideally around 30-50 cm high with a high percentage (e.g., 60%) of pickleweed (Salicornia) and complex structure of Atriplex and other species. The mouse needs access to refuge/cover on high ground, especially during highest tides in winter. It appears to be less dependent on cover in diked marshes than in tidal marshes (Geissel et al. 1988). In South San Francisco Bay, in diked marsh, harvest mice used more open and saltier pickleweed when vole populations were high, then moved into deeper and less salty pickleweed as vole populations declined (Geissel et al. 1988). In diked salt marshes, high densities of voles (Microtus) seem to force this species into marginal habitats or to become locally extirpated (Geissel et al. 1988).

Subspecies halicoetes builds ball-like nests of dry grasses/sedges on the ground. Subspecies raviventris does little nest building but may use accumulations of vegetation on the ground surface. Diet dominated by green vegetation. Will eat salt grass and pickleweed as well as some seeds. Diet influenced by availability of food plants. More green vegetation is eaten in winter. Primarily nocturnal but sometimes active during the day.

Average litter size is 3.7-4.0 young. There may be only a single litter/year in R. r. halicoetes (breeds May-November) but multiple litters in R. r. raviventris (breeds March-November).

Systems
  • Terrestrial
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Comments: Habitat consists of salt and brackish marshes, where plants provide a dense mat of cover, ideally around 30-50 cm high with a high percentage (e.g., 60%) of Salicornia (pickleweed) and complex structure of Atriplex and other species. The mouse needs access to refuge/cover on high ground, especially during highest tides in winter. It appears to be less dependent on cover in diked marshes than in tidal marshes (Geissel et al. 1988). In South San Francisco Bay, in diked marsh, harvest mice used more open and saltier pickleweed when vole populations were high, then moved into deeper and less salty pickleweed as vole populations declined (Geissel et al. 1988).

Subspecies halicoetes builds ball-like nests of dry grasses/sedges on the ground. Subspecies raviventris does little nest building but may use accumulations of vegetation on the ground surface.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Trophic Strategy

The diet of salt marsh harvest mice seems to consist mainly of salt marsh plants, such as pickle weed. These mice eat a low ration of seeds and insects also. In winter, the diet switches mainly to grasses. In a unique adaptation to its habitat, this species is apparently tolerant of drinking saline water.

Animal Foods: insects

Plant Foods: leaves; seeds, grains, and nuts

Primary Diet: herbivore (Folivore , Granivore , Lignivore)

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Comments: Diet dominated by green vegetation. Eats salt grass (DISTICHLIS) and pickleweed (SALICORNIA) as well as some seeds. Diet influenced by availability of food plants. More green vegetation is eaten in winter.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Associations

These mice do not have high population densities or high rates of reproduction, so it is not likley that they are an important food source for any one species. It is unknown if they play a role in dispersal of seeds.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Members of the genus Reithrodontomys are eaten by many predaotrs, inclduing such as hawks, egrets, snakes, and skunks, but also by introduced rats, cats, and red foxes.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Known prey organisms

Reithrodontomys raviventris preys on:
Insecta

This list may not be complete but is based on published studies.
Creative Commons Attribution 3.0 (CC BY 3.0)

© SPIRE project

Source: SPIRE

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 80

Comments: Shellhammer (1982) mapped 24 "principal populations." Recent figures are unavailable.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Global Abundance

1000 - 10,000 individuals

Comments: Shellhammer et al. (1983) estimated a total population of a "few thousand animals at the peak of their numbers each summer."

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

General Ecology

In diked salt marshes, high densities of voles (MICROTUS) seem to force this species into marginal habitats or to become locally extirpated (Geissel et al. 1988).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Life History and Behavior

Behavior

Communication in this species has not been documented. However, like most mice, their communication probably involves some combination of visual, accoustic, olfactory, and tactile cues.

Communication Channels: visual ; tactile ; acoustic ; chemical

Perception Channels: visual ; tactile ; acoustic ; chemical

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Cyclicity

Comments: Primarily nocturnal but sometimes active during the day.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Life Expectancy

Most live less than 1 year. The longest it has been seen to live in the wild is about 18 months.

Range lifespan

Status: wild:
18 (high) months.

Typical lifespan

Status: wild:
12 (high) months.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Reproduction

The mating system of salt marsh harvest mice has not been described. However, a congeneric mouse species, R. megalotis is reported to be polygynous.

Females have a long breeding season that is from March to October or November, but reproductive prospective is low. Males are reproductively active from April to September. The average litter is approximately 4. Usually a female produces only one litter per year, although they are capable of bearing two to three litters per year. This makes these mice quite different from their congener, R. megalotis, which can produce litters just about every month, provided the weather is not too cold.

Gestation periods of the genus Reithrodontomys are 21-24 days.

Occurrance of maturation events, such as eruption of incisors, opening of ear pinnae and eyes, weaning and dispersal are not reported for R. raviventris. However, in R. megalotis, these events are well documented. In this latter species, neonates weigh between 1 and 1.5 g. They are born naked and helpless. They are only 7 to 8 mm in length. They grow hair and begin to crawl by the age of 5 days, and their manidublar incisors begin to emerge through the gums byt his time also. By day 11 or 12, the eyes and ears open. Baby R. megalotis are completely weaned by about 24 days of age, and disperse shortly thereafter.

The timing of such events in R. megalotis may, or may not, be suggestive of the timing of such events in R. raviventris. Because salt marsh harvest mice are quite different from their congeners in their rate of reproduction, they may also be different in timing of developmental events.

Breeding interval: These mice typically breed once annually.

Breeding season: Breeding occurs from March to October or November.

Range number of offspring: 4 (high) .

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous

Reports of parental care in this species are not available. However, young of this genus are altricial, and require care from adults. In all mammals, females care for their young, providing them with milk, with shelter, and with protection until they reach the age of independence. It is not known if males of R. raviventris contribute to parental care.

Parental Investment: no parental involvement; altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

  • Castronova, V., W. Beachman. 1994. Beachmans's guide to the endangered species of North America. Farmington Hills, MI: Beachman Publishing Inc..
  • Masicot, P. updated: 08/19/2001. "Animal Info-Saltmarsh Harvest Mouse" (On-line). Accessed November 1, 2001 at http://www.animalinfo.org/species/rodent/reitravi.htm.
  • Ruff, S., E. Wilson. 1999. The Smithsonian Book of North America. Washighton: Smithsonian Institution Press.
  • Shellhammer, H. 1982. Reithrodontomys raviventris. Mammalian Species, 169: 1-3.
  • Webster, W., J. Jones. 1982. Reithrodontomys megalotis. Mammalian Species, 167: 1-5.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Average litter size is 3.7-4.0 young. There may be only a single litter/year in R. R. HALICOETES (breeds May-November) but multiple litters in R. R. RAVIVENTRIS (breeds March-November).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Conservation

Conservation Status

Main reasons for the low population of salt marsh harvest mice is damage of wetlands, habitat destruction, and vegetation changes. Groundwater pumping has been diminishing marsh size in particular areas, while sewage dumping has contaminated others. Much of the marsh land habitat historically used by this species has been diked or drained, and almost all marshes around the San Francisco Bay area are too small and too far apart to support large populations. The extent of habitat fragmentation makes it difficult for this species to breed and recolonize habitat.

In 1972, The San Francisco Bay National Wildlife Refuge was founded, and has protected marshes in the South Bay. The largest of these marshes is Greco Island. California has obtained several areas that supply mouse habitat: Grizzly Island and Joyce Island Wildlife Areas, Hill Slough Wildlife Area, and Peytonia Slough Ecological Reserve. Also, another recovery plan was established in 1984. This plan has aimed to conserve the salt marsh harvest mouse through acquisition of larger marsh areas to combine with existing small isolated ones; altering upper edges of most marshes to provide three species of plants as refuges for mice when they get stressed by flooding.

US Federal List: endangered

CITES: no special status

IUCN Red List of Threatened Species: endangered

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)

Version
3.1

Year Assessed
2008

Assessor/s
Whitaker Jr., J.O. & NatureServe (Hammerson, G. & Williams, D.F.)

Reviewer/s
Amori, G. (Small Nonvolant Mammal Red List Authority) & Chanson, J. (Global Mammal Assessment Team)

Contributor/s

Justification
Listed as Endangered, because its extent of occurrence is less than 5,000 km², its area of occupancy is less than 500 km², its range is severely fragmented, and there is a continuing decline in the extent and quality of its tidal marsh habitat, and the number of locations as well as the number of individuals.

History
  • 2000
    Vulnerable
  • 1996
    Vulnerable
  • 1994
    Endangered
    (Groombridge 1994)
  • 1990
    Endangered
    (IUCN 1990)
  • 1988
    Endangered
    (IUCN Conservation Monitoring Centre 1988)
  • 1986
    Endangered
    (IUCN Conservation Monitoring Centre 1986)
  • 1982
    Endangered
    (Thornback and Jenkins 1982)
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

National NatureServe Conservation Status

United States

Rounded National Status Rank: N1 - Critically Imperiled

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

NatureServe Conservation Status

Rounded Global Status Rank: G1 - Critically Imperiled

Reasons: Small fragmented range in the marshes of the San Francisco Bay area; threatened by development pressures on nontidal marshes and decreased water quality; much habitat is subject to incompatible waterfowl management.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Current Listing Status Summary

Status: Endangered
Date Listed: 10/13/1970
Lead Region:   California/Nevada Region (Region 8) 
Where Listed: U.S.A.(CA)


Population detail:

Population location: U.S.A.(CA)
Listing status: E

For most current information and documents related to the conservation status and management of Reithrodontomys raviventris , see its USFWS Species Profile

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Status

#The red-bellied harvest mouse, R. raviventris raviventris, is Endangered; the parent species is Vulnerable.
Creative Commons Attribution 3.0 (CC BY 3.0)

© Smithsonian Institution

Source: Smithsonian's North American Mammals

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Population

Population
Shellhammer et al. (1983) estimated a total population of a "few thousand animals at the peak of their numbers each summer." They also mapped 24 "principal populations." Recent figures are unavailable. The former, probably more or less continuous historical distribution has been fragmented, leaving harvest mouse populations restricted to discontinuous patches of suitable habitat. About 84% of historical tidal marshes of the San Francisco Bay area have been destroyed. Over 3,600 acres of habitat have been filled or degraded since the 1970s. Since 1982, hundreds of acres of nontidal salt marsh in the South Bay have been disced and the damage continued into at least 1989 (California DF&G 1990).

Population Trend
Decreasing
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Global Short Term Trend: Decline of 10-30%

Global Long Term Trend: Decline of 50-90%

Comments: The former, probably more or less continuous historical distribution has been fragmented, leaving harvest mouse populations restricted to discontinuous patches of suitable habitat. About 84% of historical tidal marshes of the San Francisco Bay area have been destroyed. Over 3,600 acres of habitat have been filled or degraded since the 1970s. Since 1982, hundreds of acres of nontidal salt marsh in the South Bay have been disced and the damage continued into at least 1989 (California DF&G 1990). USFWS (1990) categorized the status of this species as "declining."

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Threats

Major Threats
This species is threatened by habitat destruction or disturbance due to development, residential encroachment, intrusion of fresh water into salt marshes, marsh subsidence, and predation (especially by housecats). In many marsh habitats, there is no higher ground to escape to during high tides. Habitat within the range of the southern subspecies (R. r. raviventris) has been more severely impacted than that of the northern subspecies (R. r. halicoetes).

Most of the historical tidal marsh habitat has been lost as a result of filling for urban development and conversion to agricultural uses and commercial salt production. Upland vegetative cover adjoining tidal marshes is important cover for harvest mice during high tides and storms, but much of this habitat is no longer available due to clearing and conversion to intensive human uses. Remaining populations are relatively small, isolated, and may lack the size and full range of resources needed for long-term persistence.

Threats include continued loss of habitat to development, pollution and other changes in water quality, and encroachment by exotic plant species (e.g., invasive cordgrasses, Spartina) that do not provide suitable habitat for salt marsh harvest mice. Most areas of remaining habitat support few to no mice because of backfilling, subsidence, or vegetation changes. Salt marshes are subject to subsidence and increased tidal coverage (flooding) as a result of groundwater pumping. This reduces the extent of the broad pickleweed zone favoured by harvest mice (Shellhammer 1998).

Most of the remaining habitat is diked. Much of the habitat is managed for waterfowl and such management (e.g., lowered salinities) may not be compatible with the needs of harvest mice. Excessive inputs of fresh water (e.g., from discharges of treated municipal sewage) have altered salinity levels, marsh vegetation, and mouse food resources. See Shellhammer (1989) for a discussion of threats to diked marshes.

Much of the East Bay shoreline from San Leandro to Calaveras Point is rapidly eroding. In addition, an estimated 600 acres of former salt marsh along Coyote Creek, Alviso Slough, and Guadalupe Slough has been converted to fresh- and brackish-water vegetation due to freshwater discharge from South Bay wastewater facilities; these areas likely no longer support populations of salt marsh harvest mice.

Some habitat has been lost as a result of discing of nontidal salt marsh. Discing of wetlands, an activity not regulated by the U.S. Army Corps of Engineers, has been employed by interests seeking to obscure the Corps' jurisdiction and circumvent the Clean Water Act and the Federal Endangered Species Act.

Some harvest mice are preyed upon by feral and free-ranging cats and non-native red foxes that roam salt-pond dikes or wander from residential areas now bordering many tidal marshes.

Habitat may be threatened over the long term by the rise in sea level that is predicted to occur within the next century. In combination with reduced sediment supply caused by upstream dams and water diversions, sea level rise could result in major losses of tidal marsh habitat that would be very difficult to prevent or mitigate.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Degree of Threat: High

Comments: Most of the historical tidal marsh habitat has been lost as a result of filling for urban development and conversion to agricultural uses and commercial salt production. Upland vegetative cover adjoining tidal marshes is important cover for harvest mice during high tides and storms, but much of this habitat is no longer available due to clearing and conversion to intensive human uses. Remaining populations are relatively small, isolated, and may lack the size and full range of resources needed for long-term persistence.

Threats include continued loss of habitat to development, pollution and other changes in water quality, and encroachment by exotic plant species (e.g., invasive cordgrasses, Spartina) that do not provide suitable habitat for salt marsh harvest mice. Most areas of remaining habitat support few to no mice because of backfilling, subsidence, or vegetation changes. Salt marshes are subject to subsidence and increased tidal coverage (flooding) as a result of groundwater pumping. This reduces the extent of the broad pickleweed zone favored by harvest mice (Shellhammer 1998).

Most of the remaining habitat is diked. Much of the habitat is managed for waterfowl and such management (e.g., lowered salinities) may not be compatible with the needs of harvest mice. Excessive inputs of fresh water (e.g., from discharges of treated municipal sewage) have altered salinity levels, marsh vegetation, and mouse food resources. See Shellhammer (1989) for a discussion of threats to diked marshes.

Much of the East Bay shoreline from San Leandro to Calaveras Point is rapidly eroding. In addition, an estimated 600 acres of former salt marsh along Coyote Creek, Alviso Slough, and Guadalupe Slough has been converted to fresh- and brackish-water vegetation due to freshwater discharge from South Bay wastewater facilities; these areas likely no longer support populations of salt marsh harvest mice.

Some habitat has been lost as a result of discing of nontidal salt marsh. Discing of wetlands, an activity not regulated by the U.S. Army Corps of Engineers, has been employed by interests seeking to obscure the Corps' jurisdiction and circumvent the Clean Water Act and the Federal Endangered Species Act.

Some harvest mice are preyed upon by feral and free-ranging cats and non-native red foxes that roam salt-pond dikes or wander from residential areas now bordering many tidal marshes.

Habitat may be threatened over the long term by the rise in sea level that is predicted to occur within the next century. In combination with reduced sediment supply caused by upstream dams and water diversions, sea level rise could result in major losses of tidal marsh habitat that would be very difficult to prevent or mitigate.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Management

Conservation Actions

Conservation Actions
Although populations occur in a number of protected areas, many are probably not large enough to ensure long term persistence. There was a recovery plan completed in 1984. However, the US Fish and Wildlife Service is developing a "Tidal March Ecosystem Recovery Plan," with R. raviventris to be included in this apparently updated plan.

This mouse is protected to some extent by federal and state listings as Endangered. Several small marshes are protected in national wildlife refuges and other preserves, but few provide refuge and cover from the highest tides.

Marshes and adjacent uplands need to be protected from development and degradation. Managed, diked marshes appear to be the key to the survival of the subspecies raviventris; future management prescriptions may include the possibility of a more patchy environment with some areas of high salinities plus the acceptance of some open areas within the managed areas (Geissel et al. 1988). Shellhammer (1989) questioned whether large enough areas of diked marsh can be acquired in the near future to protect this species in perpetuity.

Up-to-date data are needed on range-wide habitat occupancy and relative abundance. Research is needed on the effects of plant salinities on water balance and habitat use of mice.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Management Requirements: Manage for vegetation structure and composition needed by mice; provide cover for refuge above highest tides; restrict foot traffic.

Biological Research Needs: Research is needed on the fffects of plant salinities on water balance and habitat use of mice.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Global Protection: Several (4-12) occurrences appropriately protected and managed

Comments: This mouse is protected to some extent by federal and state listings as Endangered. Several small marshes are protected in national wildlife refuges and other preserves, but few provide refuge and cover from the highest tides.

Needs: Marshes and adjacent uplands need to be protected from development and degradation. Managed, diked marshes appear to be the key to the survival of the subspecies raviventris; future management prescriptions may include the possibility of a more patchy environment with some areas of high salinities plus the acceptance of some open areas within the managed areas (Geissel et al. 1988). Shellhammer (1989) questioned whether large enough areas of diked marsh can be acquired in the near future to protect this species in perpetuity. See also California Department of Fish and Game (1990) for some brief general comments on management activities and needs. See recovery plan (USFWS 1984).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Relevance to Humans and Ecosystems

Benefits

R. raviventris is listed as an endangered species by the US Fish and Wildlife service. In order to protect this species, certain measures must be taken to protect its salt marsh habitat. This sort of protection probably interferes to some extent in human plans to develop, drain, dike, dam, and otherwise modify the salt marshes surrounding San Franscisco Bay. Although preservation of this habitat may not be considered a negative thing by most people, it probably affects some sections of the human economy negatively.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

These mice have little or no positive impact on people. However, they serve as food for animals which humans enjoy watching, such as hawks, owls, egrets, and foxes, so they can be considered to have an indirect positive entertainment value.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Names and Taxonomy

Taxonomy

Comments: Two subspecies are recognized: R. r. raviventris and R. r. halicoetes, which some authors have proposed as distinct species. Neither Baker et al. (2003) nor Musser and Carleton (in Wilson and Reeder 1993, 2005) recognized halicoetes as a distinct species. See Hood et al. (1984) and Nelson et al. (1984) for evolutionary relationships based on chromosomes and genic data (apparent sister-group relationship with R. montanus). Based on mtDNA data, Bell et al. (2001) determined that R. raviventris and R. montanus are indeed separate, but sister species.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Disclaimer

EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.

To request an improvement, please leave a comment on the page. Thank you!