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Alabama Beach Mouse

ALABAMA BEACH MOUSE

Photo Credit: Nick R. Holler

SCIENTIFIC NAME: Peromyscus polionotus ammobates (Bowen)

OTHER NAMES: None.

DESCRIPTION: Smallest (adults, total length =122-153 mm [4.8-6.0 in.]; weights =10.0-17.0 g [0.35-0.60 oz.]; pregnant females reaching 22-25 g [0.78-0.88 oz.]) species of Peromyscus in North America (Hall 1981b). Tail short, usually 55-65 percent of body length. Males generally smaller than females.  Brown to pale gray above, with pure white undersides and feet. A dark brown mid-dorsal stripe is common. Tail bicolored, with variable (10-80 percent of tail length) dark brown stripe on dorsal surface and pure white underneath (Howell 1939; Hall 1981b).    

DISTRIBUTION: Historic distribution was along the coastal dunes of Baldwin County, Alabama, from the western tip of Fort Morgan Peninsula eastward to the Perdido Bay inlet, including Ono Island. The type locality was a sand bar immediately west of Perdido Key inlet (Alabama Point, Bowen 1968). Type locality has been heavily developed and no longer exhibits natural characteristics. Because of extensive development throughout the Alabama Gulf Coast, the present-day distribution of the Alabama beach mouse is greatly reduced (Holliman 1983). Active populations are known to exist in areas of public ownership at Fort Morgan and within the Perdue Unit of the Bon Secour National Wildlife Refuge (Swilling and Wooten 2002). Discontinuous occupation of dune and scrub habitat between these two sites also occurs. Have been re-established at Gulf State Park. Trapping and visual surveys suggest extirpation from all areas east of Gulf State Park.

HABITAT: Typically includes primary, secondary, and scrub dunes of the coastal strand community (Bowen 1968, Rave and Holler 1992). Densities often greatest in sparsely vegetated areas within the primary dune zone. Recent research indicated that scrub habitat is more important than previously thought.  Recognition of the value of this habitat as refugia from hurricanes and other storm events has prompted formal redesignation of the Critical Habitat limit for this subspecies.  Only rarely found associated with human dwellings.  

LIFE HISTORY AND ECOLOGY: Monogamous; pair bonding strong and parental cooperation in rearing has been noted (Blair 1951, Margulis 1997, Swilling and Wooten 1992). Litter sizes range from two to eight (mode = four) (Caldwell and Gentry 1965, Smith 1966). Gestation period averages 28 days with a postpartum estrus common. Reproduction occurs throughout the year, but typically slows during summer and peaks during late fall/early winter in correlation with availability of forage seeds. A semifossorial, nocturnal rodent that digs distinctive burrows in sandy soils. Burrows typically consist of an entrance tube up to one meter (three feet) deep leading to one or more chambers (Hayne 1936, Smith 1966). An escape tunnel is normally present from the nest chamber to just below the surface. Nests of dried grasses and other fibers are found in the central chamber. Burrow openings are frequently located within vegetation. A fan-shaped plume of expelled sand is characteristic of active burrows. Entrance tunnels are blocked several centimeters (three to five inches) below surface by sand plugs, presumably for predator defense. Granivorous-omnivorous, with a majority of diet being seasonal seeds (Smith 1966, Gentry and Smith 1968, Moyers 1996). Wind-deposited seeds such as sea oats and bluestem important components of diet; acorns eaten when available. Also consumes a variety of animal foods, including both insects and vertebrates. Insects reported in diet include beetles, leaf hoppers, true bugs, and ants.  Nocturnal, with daytime activity rare; nightly movements directly affected by weather conditions. Radio tracking indicates activity throughout the night, with peaks occurring shortly after dusk and again after midnight (Lynn 2000). Capable of dispersing over five kilometers (3.1 miles) (Smith 1966) and commonly traverse 0.5 kilometers (0.31 miles) of habitat per night, but most observations indicate that individuals settle within a few hundred meters (200-1,000 feet) of their natal sites. Juveniles disperse an average of 160 meters (500 feet), effectively one home range, away from the natal site (Swilling and Wooten 2002). Dispersal distances for juvenile males and females not reported to differ. Home range size varies according to season and reproductive state. Average values reported for Alabama beach mice were 4,086 -5,512 square meters (43,981-59,330 square feet) from trapping data and 6,783-7,000 square meters  (73,011-75,347 square feet) from telemetry data, but ranges as small as 389 square meters (4,187 square feet) and as large as 29,330 square meters  (315,715 square feet) have been observed (Lynn 2000).  Home range sizes do not differ significantly between males and females.  In general, populations show little evidence of intraspecies competition with increasing densities yielding increased compaction of home ranges. This combination of tolerance and dispersal results in the formation of spatial "neighborhoods" within populations. For Alabama beach mice, approximate size of these spatial units is 550 meters (1,800 feet; linear) with occupancy by 40-70 mice. Average life span in natural populations less than nine months although common to encounter mice more than one year of age. Captures of mice known to be two years old have been reported and captive mice have reached four or more years of age. Preyed upon by the red and gray fox , great horned owl, great blue heron, weasel, striped skunk, raccoon, various snakes including coach-whip and pygmy and eastern diamondback rattlesnakes, and domestic dogs and cats.

BASIS FOR STATUS CLASSIFICATION: Habitat loss and fragmentation associated with residential and commercial real estate development single most important factor contributing to imperiled status. Existing or proposed beachfront development will substantially alter all Alabama beach mouse habitat not in public ownership. Reduction of available habitat and isolation of the remaining populations substantially increases vulnerability to the effects of tropical storms, weather cycles, predation, and other environmental factors. Substantial disagreement exists as to the current status and appropriate management protocol for the Alabama beach mouse. Various researchers have argued it is in immediate jeopardy of range-wide extinction if habitat loss is allowed to continue. This position is supported by evidence of widespread extirpation from all developed areas in the eastern portion of the historic distribution. Similar levels of development are occurring throughout the Fort Morgan Peninsula and real estate development on all private areas is proceeding rapidly.  In addition, Population Viability Analyses indicate that extinction of even the largest remaining populations is likely within 50 years if current trends continue (Oli et al. 2001). Listed as endangered by the U.S. Fish and Wildlife Service in 1986.

Author: Michael C. Wooten


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