Photo Credit: Nick R. Holler

SCIENTIFIC NAME: Peromyscus polionotus trissylepsis (Bowen)


STATUS: Storms and habitat destruction have reduced distribution from entire length of Perdido Key to a few remnant and reintroduced populations. Although there are distinct morphological and genetic differences, ecology and reproduction similar to the Alabama beach mouse. Listed as endangered by the U.S. Fish and Wildlife Service. HIGHEST CONSERVATION CONCERN.

DESCRIPTION: Shares physical characteristics with the Alabama beach mouse (Hall 1981b), but is lighter in color, with more white on the face and cheeks (Bowen 1968). Boundary between dorsal and ventral pelage does not extend as far down laterally as in the Alabama beach mouse. Dorsal tail stripe is most commonly absent. The subspecies name, trissylepsis, derives from the hypothesis that the subspecies arose from hybridization of nearby Alabama and Santa Rosa beach mice with an inland subspecies of P. polionotus (Bowen 1968).  

DISTRIBUTION: Restricted to Perdido Key. Historically, distributed along entire length of island (27.4 km [17 mi.]) starting in Alabama at Florida Point and continuing eastward to the Pensacola Bay inlet (Holler 1992). At the time of its listing, the only known population was at Florida Point. The subspecies had apparently been extirpated from all other portions of the island following Hurricane Fredrick in 1979 (Holliman 1983). By 1986, the number of mice remaining was believed to be less than 30 animals, earning it the unfortunate designation as the Most Endangered Small Mammal In North America. Between November 1986 and April 1988, 15 pairs of Perdido Key beach mice were relocated to the Johnson Beach Unit of Gulf Islands National Seashore (Holler et al. 1989).  Shortly afterward, following a series of storm events, the population at Florida Point declined and was eventually lost. Predation by domestic cats contributed significantly to the demise of this population. Starting in 2000, a new population was reestablished on Perdido Key State Recreation Area. The Johnson Beach and Perdido Key Recreation Area populations are the only remaining sites known to be inhabited.

HABITAT:  Similar to the Alabama beach mouse. Perdido Key is a narrow barrier island and contains only limited areas of scrub habitat.  In occupied habitats, found in all areas from the frontal dunes to within several feet of the northern bay.

LIFE HISTORY AND ECOLOGY: Despite distinct morphological and genetic differences, the ecology of this subspecies is similar if not identical to the Alabama beach mouse. Captive breeding of the subspecies has proven difficult, which is unusual for this species and small behavioral differences have been reported. Reproduction, food choice, and activity patterns are similar to other subspecies. Marked variation between the Florida Point population and the reestablished Johnson Beach population was observed for some characteristics. Subadults at Johnson Beach dispersed an average of 675.9 meters (2,217 feet) while at Florida Point the average was 173.1 meters (568 feet). Other estimates, including neighborhood size and seasonal movements yielded similar differences. These differences are believed to reflect variation in habitat quality. The Johnson Beach site was heavily impacted by storm damage and has been slower to recover.   

BASIS FOR STATUS CLASSIFICATION: As with the Alabama beach mouse, loss of habitat to real estate development was the primary underlying factor resulting in this subspecies being listed as endangered. Starting with Hurricane Fredrick in 1979, extensive human-induced habitat fragmentation has overridden the Perdido Key beach mouse’s natural ability to reestablish itself after storm events, thus resulting in reduced population numbers. Listed as endangered by the U.S. Fish and Wildlife Service in 1986.

Author: Michael C. Wooten