Florida Salt Marsh Vole

Microtus pennsylvanicus dukecampbelli

Description

The Microtus pennsylvanicus dukecampbelli (Florida salt marsh vole), a subspecies of the widespread meadow vole or field mouse (Microtus p. pennsylvanicus), is a short-tailed rodent about 6.5-7.5 in (17-19 cm) in total length. It is brownish black above and gray below, with a blunt head and short, rounded ears. It is distinguished from the meadow vole by its larger size, darker color, smaller ears, and certain skull characteristics.

Behavior

Because of its recent discovery and rarity, the life history and reproductive behavior of the Florida salt marsh vole have not been well studied. Typically, voles are active both day and night and are good swimmers. They feed on a great variety of plant matter, including grass, bark, seeds, and roots. The meadow vole is the most fecund mammal in North America. It reproduces throughout the year over much of its range and is capable of producing up to 17 litters of four to six young each year. After a gestation period of about 20 days, newborn voles grow rapidly and are weaned at about 14 days. They are an important prey for snakes, foxes, hawks, and owls.

Habitat

The Florida salt marsh vole inhabits a single salt marsh on the Gulf Coast of Florida. Vegetation in the marsh consists of smooth cordgrass (Spartina alterniflora), black rush (Juncus roemerianus), and salt-grass (Distichlis spicata).

Distribution

This subspecies was described in 1982 from specimens taken along the Waccasassa Bay in Levy County, Florida. It is thought to be a relict of a population dating from a period of the Pleistocene Era 8,000-30,000 years ago. In the past, lower sea levels exposed areas along the west coast of Florida that are now submerged. This coastal prairie and savannah provided habitat for voles. Meadow vole fossils have been found in Alachua, Citrus, and Levy counties. Today the closest meadow vole population is in Georgia, about 310 mi (500 km) to the north. The Florida salt marsh vole has not been found outside the single salt marsh on Waccasassa Bay. The marsh is privately owned, and at this time there are no plans for its development. Searches to discover additional populations in the coastal marshes of Levy and Citrus counties have proven unsuccessful. During the field work that discovered the subspecies, only 31 voles were taken. In a 1989 survey, only a single male vole was captured.

Threats

With its extremely limited range and small species population, the Florida salt marsh vole is extremely vulnerable to extinction. Its decline appears to have been caused by naturally occurring climatic changes that have gradually turned coastal prairie habitat into woodland unsuitable for voles. This isolated subspecies is the last remnant of a much larger and wide-ranging population. It is likely that the recent drop in the Florida salt marsh vole population was caused by Hurricane Elena in August 1985. That storm remained stationary off the coast near Waccasassa Bay for 24 hours. The Florida salt marsh vole could be rendered extinct by another such hurricane.

Conservation and Recovery

Because of its designation as an Endangered species, the Army Corps of Engineers must consider the conservation of the Florida salt marsh vole when evaluating any permit request to alter the animal's salt marsh habitat.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

References

Bentzien, M. M. 1989. "Florida Saltmarsh Vole Survey." U.S. Fish and Wildlife Service, Jacksonvile, Florida.

Woods, C. A., et al. 1982. "Microtus pennsylvanicus (Rodentia: Muridae) in Florida: a Pleistocene Relict in a Coastal Saltmarsh." Bulletin of the Florida State Museum of Biological Science 28(2):25-52.