St. Andrew Beach Mouse

Peromyscus polionotus peninsularis

Description

Peromyscus polionotus peninsularis (St. Andrew beach mouse) had a very pale, buff-colored head and back with extensive white coloration underneath and along the sides, with two distinct rump color pigmentations, one a tapered and the other a squared pattern, which extended to the thighs. In specimens studied, the head and body lengths average 2.95 in (7.5 cm), tail mean length 2.05 in (5 cm), and hind foot mean length 0.73 in (2 cm).

Behavior

Beach mice are nocturnal, and the frequency of their activities is governed by the brightness of the moon. They feed on the fruits and seeds of dune plants, particularly sea oats and sea rocket. When seeds are scarce in winter, the mice may feed on invertebrates, foraged from the sand. Once established in an area, beach mice tend to remain there for life or until a catastrophic event, such as a hurricane, makes the habitat untenable. Some shifting of territories occurs within a limited range. When a segment of habitat is depleted by storms, mice in neighboring segments of beach tend to expand their territories, gradually repopulating a depleted area. Mating pairs typically share burrows and foraging duties. The female produces a litter of two to seven young, and is capable of bearing 80 or more young during her lifetime. Juveniles develop quickly and may reach sexual maturity in as little as six weeks. Litters are produced regularly every 26 days. Mortality among young mice is very high due to predators.

Habitat

Trap surveys at Crooked Island and on the St. Joseph Peninsula documented the presence of St. Andrew beach mouse on frontal dunes, as well as on primary and secondary dunes. These results support other surveys which found that the greatest concentration of most other beach mice subspecies occurred in these habitat types. This concentration is due in part to a predominance of plants whose seeds and fruits are important seasonal constituents of beach mouse diets.

Scrub dunes on Santa Rosa Island offered abundant food and cover for the Santa Rosa beach mouse (Peromyscus polionotus leucocephalus ). Scrub dunes may also function as refugia during and after storms and as a source for recolonization of storm-damaged dunes. Their use by the St. Andrew beach mouse is not well documented, but in 1986 mice were collected from well-vegetated back dunes on Crooked Island, and in 1996 they were captured in secondary dunes immediately adjacent to scrub dunes.

Distribution

Beach mice subspecies historically occurred on both the Atlantic Coast of Florida from St. Johns through Broward counties and the eastern Gulf of Mexico coast from Gulf County, Florida, to Baldwin County, Alabama. The former range of the St. Andrew beach mouse as likely extending from the St. Joseph Spit (Peninsula) northwest along the coastal mainland adjacent to St. Joseph Bay, to Crooked Island at the East Pass of St. Andrews Bay. This range also included about 1 mi (1.6 km) of mainland sand dune habitat east of the landward end of the St. Joseph Peninsula to Money Bayou on the Gulf of Mexico.

Beach mouse populations can at times undergo great seasonal variations in numbers. Prior to human disturbance, hurricanes and tropical storms likely were the dominant factors producing rapid and possible widespread impacts on beach mice and their habitat. Because the St. Andrew beach mouse evolved under adverse weather conditions, the subspecies developed the capability to survive and recover from these periodic severe impacts to its numbers and habitat. During the twentieth century, however, more rapid land development, dune encroachment by pedestrians and vehicles, and military activities began to contribute to the decline. Hurricane Eloise split Crooked Island into east and west segments in 1975, and multiple attempts to collect beach mice from the western segment during the early and mid-1980s were unsuccessful. During this same period, trap surveys collected small numbers of beach mice on the eastern segment. Limited trap and track surveys during the late 1980s found no evidence of beach mice within undeveloped coastal mainland habitat between Crooked Island and Money Bayou. Surveys revealed that mice still existed on Crooked Island East and also occurred within St. Joseph Peninsula State Park. In 1992 the Crooked Island East population was estimated at 150 mice and the population within St. Joseph Peninsula State Park at 500 mice. Extensive surveying of primary, secondary, and scrub dune habitat on Crooked Island East during the 1990s revealed that the beach mouse population there no longer existed. Similar efforts at Cape San Blas on Eglin Air Force Base and U.S. Coast Guard properties yielded no mice. Three hundred thirty-eight individuals were captured in 1992 within St. Joseph Peninsula State Park. In October 1995, Hurricane Opal caused extensive coastal damage to the Florida panhandle. Habitat impacts within the St. Joseph Peninsula appeared more extensive outside St. Joseph Peninsula State Park boundaries, and researchers calculated that the total population of St. Andrew beach mice remaining after the storm was around 190 individuals. The a trap survey within St. Joseph Peninsula State Park in February 1997 collected 117 mice, and it is estimated that St. Joseph Peninsula State Park currently may support between 300-500 mice. The estimate represents a significant increase over the 1995 post-Hurricane Opal survey and is comparable to the last pre-Hurricane Opal survey within the park.

Threats

Natural events and manmade activities that have impacted the St. Andrew beach mouse and its habitat include severe storms, land development, military exercises on Crooked Island, dune encroachment by vehicles and pedestrians, and non-storm related shoreline erosion. Between 1871 and 1995, nearly 50 hurricanes or tropical storms occurred within 90 mi (144 km) of St. Joe Bay, which is about midway within the historic range of the species. In the twentieth century, storm strength, proximity to the historic range, and degree of habitat impact have been especially intense during the last 30 years. In 1975, Hurricane Eloise breached Crooked Island, dividing it into two segments and severely eroding and fragmenting dunes, particularly within the newly-formed western segment. In 1985, Hurricane Kate scoured dunes within the entire range of the St. Andrew beach mouse. These storms caused extensive blowouts in the high dunes throughout the St. Joseph Peninsula. In 1995, Hurricane Opal, which made landfall 85 mi (136 km) west of St. Joe Bay, severely damaged and fragmented frontal and primary sand dunes within the historic range of the beach mouse. The most seriously impacted areas were the unoccupied habitat from Crooked Island to Mexico Beach. Fifty percent of the population within the St. Joseph Peninsula may have been lost, with the greatest impacts occurring south of St. Joseph Peninsula State Park. Although the population within the St. Joseph Peninsula State Park has since recovered, additional land development, consecutive years of severe weather or a single season of intense storms over, or in close proximity to, currently occupied habitat may result in extinction of the subspecies.

Land development has been primarily responsible for the permanent loss of St. Andrew beach mouse habitat. Historic maps suggest that earlier construction of State Road 98 and incorporated development from the vicinity of Port St. Joe to Mexico Beach occurred within one or more types of coastal sand dune habitat. Little or no suitable habitat currently occurs at the seaward side of some of these incorporated areas. Intense development could act as a barrier to migration, isolating mice within these habitat segments and making them more vulnerable to local extinction from one or more threats.

Conservation and Recovery

In November 1997 and January 1998, a total of 38 St. Andrew beach mice, including mated pairs and pregnant females, were translocated from St. Joseph Peninsula State Park to East Crooked Island, Tyndall Air Force Base. Post-release trapping and radio telemetry surveys revealed successful dispersal and reproduction by these introduced beach mice. Track observations indicated movement up to 1.6 mi (2.5 km) from one of the release sites. Offspring of these founders colonized habitat outside the reintroduction area.

The St. Andrew beach mouse is listed as a Florida State endangered species. Chapter 39-27.002 of the Florida Administrative Code prohibits the take, possession, or sale of endangered species except as authorized by specific permit for the purpose of enhancing the survival potential of the species. The law does not provide for the protection or conservation of a listed species' habitat.

Federal agency actions that are expected to require consultation include mission-related activities authorized or carried out by Tyndall Air Force Base on Crooked Island and by Eglin Air Force Base at the Cape San Blas unit, following any translocation of beach mice to these locations. The U.S. Fish and Wildlife Service's experience with other beach mice indicates that, with planning, beach mouse conservation and military activities are compatible.

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/

Reference

U. S. Fish and Wildlife Service. 18 December 1998. "Determination of Endangered Status for the St. Andrew Beach Mouse." Federal Register 63(243): 70053-70062.