RYSER: VIRGINIA OPOSSUMS (DIDELPHIS VIRGINIANA) IN FLORIDA


(1987). So far there has been no study of an opossum population in Florida, an
environment that differs, particularly in temperature regime, markedly from that of
other studied populations in Wisconsin or Virginia. Moreover, few attempts have been
made to identify the factors that could account for the often considerable individual
variation in space use and activity (Seidensticker et al. 1987; Kissell and Kennedy
1992).


 ACKNOWLEDGEMENTS


 I am most grateful to John F. Eisenberg and Melvin E. Sunquist for making this study possible and for
making valuable comments on the manuscript Anonymous reviewers also contributed to the improvement of the
manuscript. I also especially thank Debra Wright for her cooperation in field work.


 STUDY SITE AND METHODS


 The study was conducted at the Katharine Ordway Preserve of the University of
Florida, located 40 km east of Gainesville in Putnam County, north-central Florida.
The 37 km2 tract consists of a mosaic of habitat types (see Franz and Hall 1991 for
details): Permanent and temporary lakes and ponds, freshwater marshes, swamp
forests, mesic hardwood hammocks, sand live oak hammocks, sand hill high pine
forests (tree cover dominated by Pinus palustris and Quercus sp., ground cover
dominated by wiregrass Aristida stricta), and grass-dominated areas derived from
former agricultural lands (old fields, pastures, and orange groves). Maximum
elevation is 55 m above sea level.
 The climate is characterized by hot, humid summers and cool, mild winters with
 freezing occurring at least on a few days or nights. Mean daily maximum and
 minimum temperatures are 26.70C and 14.0C, respectively, varying from 19.3/5.90C
 in January to 32.5/21.70C in July and August. Mean annual rainfall is 133 cm, with
 60% falling in the summer months May to September (data for Gainesville, from the
 National Oceanic and Atmospheric Administration).
 Information on the spatial organization of opossums and its dynamics was
 gathered by trapping and radio-tracking opossums mostly in an approximately 8-km2
 core study area in the center of the preserve from January 1986 to February 1988.
 Opossums were trapped in Tomahawk live-traps baited with fish and dry dog food. In
 1986 and early 1987, during the weeks prior to the breeding seasons, I attempted to
 trap all opossums in the study area, resulting in 1028 trap-nights. From March 1987 to
 February 1988, D. Wright and myself conducted four trapping sessions with 140 trap
 sites covering most of the preserve. During each trapping session in March/April,
 July/August, October/November and December-February we ran the trap lines for 6 to
 8 days. Opossums were measured, ear-tagged at their first capture, and pouch young