POPULATION-STRUCTURE, BODY-MASS, ACTIVITY, AND ORIENTATION OF AN AQUATIC SNAKE (SEMINATRIX-PYGAEA) DURING A DROUGHT

The snout-vent length, tail length, weight, sex, activity, and orienta tion of a population of swamp snakes (Seminatrix pygaea) in north-cent ral Florida were recorded from 1985 through 1990. A small temporary po nd was monitored for 1343 days, using a drift fence - pitfall trap sam pling regime. I captured 123 different snakes, plus 45 recaptures. Juv eniles comprised 89% of the snakes at the pond. Females were generally longer and weighed more than males, although regression analysis show ed no differences between the sexes in the relationship of length vers us wet body mass. Males had longer tails than females. The sex ratio o f snakes with a snout - vent length of more than 150 mm was 1:1. Activ ity occurred throughout the year but peaked during summer. Hydroperiod and weather conditions did not appear to influence snake activity. Du ring the latter years of the study, a regional drought that began in t he mid-1980s became quite severe. However, drought had little direct e ffect on overland migration or body condition but caused snakes to lea ve or to shorten the amount of time they spent within the pond basin. Snakes immigrated and emigrated nonrandomly; orientation was directed to and from the nearest large water body. Certain temporary ponds may comprise developmental habitat for Seminatrix pygaea. The dynamic wet- dry climatic cycles in southeastern North America may lead to the form ation of metapopulations in some aquatic snakes.