Seasonal Habitat Use by River Otters and Everglades Mink in Florida

Abstract

Seasonal habitat use by river otters (Lutra canadensis) and Everglades mink (Mustela vison evergladensis) was documented in the Big Cypress Swamp, Florida, using line transects of chalk-dusted trackboards and anal scent attractant. Response to scent was species-specific in late wet season, indicating that mating occurs in autumn, when water levels are high in marshes and swamps. Mustelids retreated from marshland as it dried, and most had moved to permanent ponds in the late dry season. This period of concentrated aquatic food coincides with lactation in mink. Use of line transects with olfactory attractants may enable monitoring of otter and mink population levels and trends on a regional or statewide scale, but rigorous testing of the technique is needed. J. WILDL. MANAGE. 46(2):375-381 The river otter is included in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (U.S. Fish and Wildlife Service 1977). Treaty obligations require determination that otter harvest for export is not detrimental to the species before export permits are issued (Endangered Species Sci. Auth. 1978). The Everglades mink is listed as threatened by the Florida Game and Fresh Water Fish Commission (1980). Protected status has increased interest in these mustelids, but little is known of their biology in Florida. Information from reports by otter trappers was presented by McDaniel (1963). The scattered information available on Everglades mink has been reported by Layne (1974) and Brown (1978), and new data were presented by Smith (1980). Both species occur in the Big Cypress Swamp in southwestern Florida. The objective of our study was to use a measure of relative abundance, adapted from the scent station technique reported by Linhart and Knowlton (1975) and Linhart et al. (1977), to document seasonal habitat use by otters and mink within a large wetland in South Florida. Our research was funded by an NIH Biomedical Grant through the University of Florida Division of Sponsored Research. Work in the Fakahatchee Strand State Preserve was encouraged by J. A. Stevenson and K. C. Alvarez and supported in the field by R. Goble and R. Baker, all of the Florida Department of Natural Resources. We thank D. B. Barbour, J. Jones, B. Tatje, and J. Thompson for assistance in the field.