Southeastern Beach Mouse, Anastasia Island Beach Mouse

Peromyscus polionotus niveiventris, Peromyscus polionotus phasma

Description

The Anastasia Island beach mouse and southeastern beach mouse are large subspecies relative to other beach mice. Ten adult Anastasia Island beach mice and ten southeastern beach mice averaged 5.4 in (14 cm) in total length, including a tail length of 2 in (5 cm). Adult Anastasia Island beach mice typically weigh from 0.4-0.63 oz (11-18 g), but pregnant females may weigh 0.70-1.05 oz (20-30 g). The coloration of the Anastasia beach mouse is light buff dorsally, white underparts, a unicolor tail, and indistinct white markings on the nose and face. The southeastern beach mouse is slightly darker than the Anastasia Island beach mouse, but paler than inland populations of the Anastasia mouse.

Behavior

Anastasia Island beach mice eat seeds of sea oats, railroad vine, and prickly pear cactus, and it is assumed that the diet of the southeastern beach mouse is the same. Beach mice feed on sea oats and beach grasses. The sea oats must be blown to the ground for the mice to eat. During the spring and early summer when seeds are scarce, beach mice may eat invertebrates.

The young reach maturity at six to eight weeks. Reproduction may occur throughout the year, but peak population levels usually occur in the winter.

Habitat

Both the Anastasia Island and southeastern beach mice are found in coastal dunes. The most seaward vegetation typically consists of sea oats, dune panic grass, railroad vine, beach morning glory, and camphor weed. Further landward, vegetation is more diverse, including beach tea, prickly pear cactus, saw palmetto, wax myrtle, and sea grape.

Anastasia Island beach mice have been trapped from sea oats and bare sandy areas on Anastasia Island, as well as in woody vegetation as far as 1,800 ft (548.6 m) inland. Both beach dunes and adjacent inland areas of scrub vegetation were used by the mice. The ideal habitat for the Anastasia island beach mouse contains patches of bare, loose, sandy soil. The presence of sea oats is not a requirement for the mouse; they also occur in sandy areas with broomsedge. The scrub adjoining these dunes is populated by oaks and sand pine or palmetto. A study conducted on Merrit Island indicated that the southeastern beach mice may prefer open sand habitat with clumps of palmetto and sea grapes, or dense scrub habitat dominated by palmetto, sea grape, and wax myrtle; over seaward habitat with sea oats.

Distribution

The Anastasia Island beach mouse was known historically from the vicinity of the Duval-St. Johns County line southward to Matanzas Inlet, St. Johns County, Florida. It currently occurs only on Anastasia Island, primarily at the Anastasia State Recreation Area and Fort Matanzas National Monument ends of the island, although beach mice still occur at low densities in remnant dunes along the entire length of the island.

The original distribution consisted of about 50 linear mi (80 km) of beach; current populations occupy about 14 linear mi (22.5 km) of beach with possibly only 3 mi (5 km) supporting viable populations. The width of the occupied habitat varies; most of the dunes on the island are much narrower than the original dune system due to residential construction. The original distribution of the southeastern beach mouse was from Ponce (Mosquito) Inlet, Volusia County, southward to possibly as far south as Miami Beach. It is currently restricted to Canaveral National Seashore to 7 mi (11 km) north of Volusia-Brevard County line. This stretch encompasses the Canaveral National Seashore, Merritt Island National Wildlife Refuge, and Cape Canaveral Air Force Station. Additional scattered localities include the Sebastian Inlet State Recreation Area, Seaview Subdivision, Treasure Shores Park, and Turtle Trail Public Beach Access area. Formerly, this subspecies occurred along about 175 mi (280 km) of Florida's southeast coast; it now occupies about 50 mi (80 km) of beach. Although at some sites southeastern beach mice can be found as far as 0.6 mi (1 km) inland, most available habitat is extremely narrow. The subspecies survives in good numbers in dunes only 3-10 ft (1-3 m) wide in Indian River County, where it probably also uses adjacent interior coastal strand habitat.

Viable populations of the Anastasia Island beach mouse currently occur at Anastasia State Recreation Area and Fort Matanzas National Monument. The subspecies persists on Anastasia Island at points between these two sites, but due to beach front development these areas are not likely to support beach mice far into the future. Anastasia Island beach mouse numbers fluctuate seasonally between two and 90 mice per acre (1 acre = .4 hectare).

Large, healthy populations of the southeastern beach mouse are found on the beaches of Canaveral National Seashore, Merritt Island National Wildlife Refuge, and Cape Canaveral Air Force Station. The distribution of this subspecies over the rest of the historical range, however, is more limited in numbers and fragmented.

Threats

Beach mice predators include snakes, bobcats, foxes, raccoons, skunks, owls, and feral cats and dogs. Feral house cats can reduce beach mouse populations and can be problem for the Anastasia Island beach mouse. Predation from house cats and competition from house mice may be restricting the distribution of southeastern beach mice at the north end of Canaveral National Seashore. Leased homes are located in this portion of the Seashore, and the area receives nearly 500,000 visitors a year. This places a heavy demand for trash and liner control, and the Seashore has taken measures to reduce the impacts of these human activities on beach mice.

The Anastasia Island and southeastern beach mice live in dynamic habitats exposed to recurring tropical storms. Historically, beach mice populations have fluctuated in response to such changes. Because of the current disjunct populations, beach mouse populations probably fluctuate over periods of many years, and the long-term persistence of a given population may depend on the ability of mice from adjacent parts of the range to recolonize beaches.

The Anastasia Island beach mouse has lost most of its historical habitat. The northern two-thirds of the historic distribution is now mostly unsuitable for beach mice due to development. Anastasia Island comprises the southern one-third of the historic range of this subspecies, and while beach mice are still found along most of the island's beaches, the only remaining viable populations are believed to be those at Anastasia State Recreation Area and Fort Matanzas National Monument. Due to the high density of beach homes along most of this coast, it is unlikely that habitat restoration sufficient to support beach mice can be done, and it is unlikely that the species can be fully recovered. The remaining viable populations could be exterminated by a single tropical storm, with much of the habitat destroyed at the same time.

Conservation and Recovery

The managers of public beaches within the range of the Anastasia Island and southeastern beach mice currently restrict beach access to designated crossovers to minimize the impacts of humans on the dune systems. Since public beaches on Florida's east coast receive heavy public use, it is essential that access continue to be so restricted. Vehicular access is allowed on beaches on Anastasia Island, and at high tide vehicles sometimes enter the dunes, so that efforts to prevent habitat damage are important.

The National Park Service is working to maintain good Anastasia beach mouse habitat on Fort Matanzas National Monument and has worked closely with the U.S. Fish and Wildlife Service (FWS) in reviewing management and projects affecting beach mice. The Division of Recreation and Parks has successfully reduced feral cat populations in the recreation area, and this has benefitted beach mice. Cats may need to be removed periodically.

In 1992-1993, the Anastasia Island beach mouse was reintroduced to Guana River State Park in St. Johns County, historical habitat for the subspecies. Guam River State Park is 9 mi (14 km) north of the existing population of beach mice at Anastasia State Recreation Area. Fifty-five mice (27 females and 28 males) were trapped at Fort Matanzas National Monument and Anastasia State Recreation Area and placed in soft-release enclosures at the state park. Follow-up trapping was conducted six months later, and the entire 4.2 mi (7 km) length of the park was occupied by beach mice; 34 were captured and it was estimated that the population totaled 220. The reintroduction has been successful thus far, despite severe northeasterly storms which caused considerable beach erosion following the releases. The population is still small, however, and it is not yet certain that limited dune habitat at the park will maintain a viable population of beach mice.

The southeastern beach mouse occurs on Canaveral National Seashore, managed by the National Park Service; in Merritt Island National Wildlife Refuge, managed by the FWS; and the Cape Canaveral Air Force Station, managed by the U.S. Air Force.

Contingency plans should be prepared to take Anastasia Island beach mice into captivity if a catastrophic event causes populations drop to a level at which chances of survival in the wild decrease significantly. If either the Fort Matanzas National Monument or the Anastasia Island State Recreation Area population becomes extirpated, consideration should be given to taking mice from the remaining population into captivity for breeding. The FWS's Cooperative Wildlife Research Unit at Auburn University already maintains breeding colonies of Choctaw-hatchee, Perdido Key, and Alabama beach mice, and would be an appropriate facility to establish a breeding colony of the Anastasia Island beach mouse.

Contacts

National Marine Fisheries Service
1315 East-West Highway
SSMC3
Silver Spring, Maryland 20910

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

U.S. Fish and Wildlife Service. 1993. Recovery Plan for the Anastasia Island and Southeastern Beach Mouse. Atlanta, Georgia. 30 pp.