| The goals of this research were to estimate home range size, daily movements, home range overlap, nest success, nest site selection, hatchling survival, hatchling abundance, growth rates, body condition, and food habits of American alligators (Alligator mississippiensis), in east Texas wetlands.;Alligator home range size and daily movements were most affected by sex, season, size, and year, but alligators used smaller home ranges and executed shorter movements than most other estimates throughout the alligator's geographic range. Alligators in inland wetlands may be more constrained than coastal individuals (occupying larger, relatively contiguous coastal marshes), as inland alligator home ranges and movements were restricted by overall wetland size, water level fluctuations, high population densities, and/or exotic invasive aquatic plants.;As part of this study, 30 nests were monitored. Nest circumference, year, and time during incubation exerted the greatest influence on nest survival. Most habitat variables were consistent throughout and within study sites, where alligators tended to select nest sites near (< 5 m) a large tree, far (> 150 m) from open water, and within areas with (> 50%) shallow marsh habitat. Variation in nest success, nest site selection, and hatchling survival are likely attributable to fluctuating water levels and habitat management practices.;Growth rates and condition were also estimated through an intensive mark-recapture study from 2003--2008, where 1064 alligators, ranging in size from 20.9 cm to 363.5 cm (total length), were captured, and 472 alligators were recaptured, ranging in size from 25.4 cm to 292.1 cm. Similar to growth rates, condition varied among wetlands and size classes, however condition improved as alligator size increased. Overall, alligators exhibited faster growth rates, but were in poorer body condition than reported throughout their range. This trade-off may be a factor of increased number of vacant breeding territories after harvest of large individuals, high population densities, food availability, and/or habitat conditions.;In 2006--2008, 62 alligator diet samples were obtained from alligators ranging in size from 94.7 cm to 386.0 cm (total length). Nearly all diet samples contained some sort of organic by-catch and/or non-food items (i.e., woody debris, aquatic plants, seeds, rocks, fishing tackle, etc.). Alligators had similar diets between sexes, however, non-breeding size (< 1.83 m in total length) alligators consumed more invertebrate prey items by weight and percent occurrence than breeding size alligators. Alligators apparently forage opportunistically, and any possible geographic differences in food habits among populations are most likely influenced by food availability.;Several key components influencing alligator populations (i.e., nest success, hatchling survival, home ranges, movements, diet, body condition, and growth rates) can be affected by specific habitat characteristics such as water levels, extent of available habitat, and presence of exotic invasive plants. More specifically, removal of exotic invasive plants should be encouraged in order to provide important habitat for alligators. Two common techniques for the removal of aquatic vegetation are spraying with herbicides and mechanically harvesting, both of which need to be properly timed and at the right intensity. In addition, to promote better nest success and hatchling survival, water levels within reservoirs should remain consistent during the nesting season (i.e., July--September). By keeping water at constant levels, female alligators can safely select nest sites above high water marks and shallow marsh habitat for hatchlings will remain available. Although water levels can be maintained by varying rates of discharge, this may not be possible in every year or at every wetland containing alligators. Therefore, it remains important to understand the relationship between water levels, nest success, and hatchling survival and to incorporate water levels into population and harvest models for American alligators. (Abstract shortened by UMI.)... |
