Viability analysis of endangered Gulf Coast beach mice (Peromyscus polionotus) populations

Beach mice, endangered subspecies of oldfield mice (Peromyscus polionotus), occur in a few, isolated populations along the Gulf Coast of Alabama and F lorida, USA. To provide information needed for the management of these spec ies, we conducted population viability analyses (PVA) using a stochastic di fferential equation (Wiener-drift) model applied to long-term demographic d ata for four populations of beach mice. In the absence of catastrophic even ts, the probability that the mouse populations would decline to one mouse r anged from 0.002 for the population of Alabama beach mice (P. p. ammobates) at the Perdue unit of Bon Secour National Wildlife Refuge (BSPU) to 1.00 f or the Perdido Key beach mouse (P. p. trissyllepsis) population at Gulf Isl and National Seashore (GINS). Modal time to extinction for those sample pat hs reaching extinction ranged from 5 years for the Fort Morgan population o f Alabama beach mice to 21 years for the GINS population of Perdido Key bea ch mice. When the BSPU data set was extended to include data collected foll owing Hurricane Opal, the probability of extinction increased to 0.479. If catastrophic events, which are frequent in the Gulf Coast habitats, are con sidered, virtually all populations of beach mice appear in substantial dang er of extinction unless current levels of habitat fragmentation are reverse d. In addition, ongoing development continues to reduce or fragment the hab itat exacerbating the already precarious existence of these mice. It is our conclusion that the results obtained from the PVA analyses provide indepen dent evidence that further loss of beach mouse habitat (including the scrub dune component) should be avoided, and that populations should be re-estab lished within their historic range wherever feasible. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.