Animal Info - Saltmarsh Harvest Mouse

Reithrodontomys raviventris

Status: Vulnerable

1. Profile (Picture)
2. Tidbits
3. Status and Trends (IUCN Status, Countries Where Currently Found, Population Estimates, History of Distribution, Threats and Reasons for Decline)
4. Data on Biology and Ecology (Weight, Habitat, Gestation Period, Birth Season, Maximum Age, Diet, Behavior, Social Organization)
5. References

Profile

Pictures: Saltmarsh Harvest Mouse #1 (5 Kb GIF) (Calif. Fish & Game); Saltmarsh Harvest Mouse #2 (128 Kb JPEG) (Smith. Inst.)

The saltmarsh harvest mouse weighs 8 - 14 g (0.3 - 0.5 oz.). It lives in salt marsh characterized by salt marsh herbs, grasses and reeds. Stems and leaves of salt marsh plants are its major food source. Insects and seeds are also eaten occasionally. It is able to drink salt water.

Grass nests are constructed by the saltmarsh harvest mouse. The nests are usually above ground in grass, low shrubs, or small trees. This mouse is mainly nocturnal and is active all year long. It apparently is a good swimmer. Except during the breeding season, it appears to be solitary. Very few of these mice live as long as 1 year in the wild.

The saltmarsh harvest mouse has only been known from areas north and south of San Francisco Bay, entirely within the narrow belt of wetlands surrounding the Bay. Its range continues to shrink because of habitat loss due to the draining and filling of wetlands for industrial and suburban development.

Tidbits

*** The saltmarsh harvest mouse is well adapted to live in salt marshes, being one of the few mammals that can drink salt water.

*** American harvest mice, such as the saltmarsh harvest mouse, are generally not considered to be harmful to agriculture.

Status and Trends

IUCN Status:

1960's: Rare
1970's - 1994: Endangered
1996: Vulnerable (Criteria: A1c+2c)
2000 - 2004: Vulnerable (Criteria: A1c+2c, B1+2c) (IUCN 2004)

Countries Where the Saltmarsh Harvest Mouse Is Currently Found:

2004: Occurs in the USA (California) (IUCN 2004).

Population Estimates:

[Note: Figures given are for wild populations only.]

WORLD (USA)
- 1993: Probably less than 2000 (WCMC/WWF 1997y)

History of Distribution:

By 1966 the saltmarsh harvest mouse only occurred north and south of San Francisco Bay, California, USA, entirely within the narrow belt of wetlands surrounding the Bay. Its range continues to shrink because of habitat loss. Approximately 80% of its original habitat has been lost. (WCMC/WWF 1997y)

Distribution Map #1 (3 Kb GIF) (Smith. Inst.)
Distribution Map #2 (10 Kb) (NatureServe Expl.)

Threats and Reasons for Decline:

The major reason for the decline of the saltmarsh harvest mouse has been habitat loss due to the draining and filling of wetlands for industrial and suburban development. By 1989, 80% of its known original habitat had been lost (Lidicker 1989).

Data on Biology and Ecology

Weight:

The saltmarsh harvest mouse weighs 8 - 14 g (0.3 - 0.5 oz.).

Habitat:

The saltmarsh harvest mouse lives in salt marsh characterized by salt marsh herbs, grasses and reeds. This habitat provides dense cover with a network of spaces underneath. (WCMC/WWF 1997y)

The saltmarsh harvest mouse is found in the California Floristic Province Biodiversity Hotspot (Cons. Intl. 2005).

Gestation Period:

Reported gestation periods for the genus Reithrodontomys are 21 - 24 days.

Birth Season:

All year except during cold winters.

Maximum Age:

Most live less than 1 year. The maximum observed longevity in the wild is about 18 months.

Diet:

The saltmarsh harvest mouse eats stems and leaves of salt marsh plants. Insects and seeds are also eaten occasionally. It is able to drink salt water.

Behavior:

The saltmarsh harvest mouse builds spherical nests of grass about 150 - 175 mm (6 - 7") in diameter. The nests are usually built above ground in grass, low shrubs, or small trees. Some winter nests are constructed in burrows and small crevices. It also appropriates the nests of song sparrows and uses the ground runways of other rodents.

The saltmarsh harvest mouse is mainly nocturnal and is active all year long. It apparently is a good swimmer.

Social Organization:

The saltmarsh harvest mouse appears to be solitary outside of the breeding season.

References

Burton & Pearson 1987, Calif. Dept. Pest. Reg., Calif. Fish & Game, Cons. Intl. 2005, IUCN 1969, IUCN 1994, IUCN 1996, IUCN 2000, IUCN 2003a, IUCN 2004, Lidicker 1989, NatureServe Expl., Nowak & Paradiso 1983, Smith. Inst., WCMC/WWF 1997y

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Last modified: March 11, 2005;