The Biophysical Ecology of the Alligator: Heat Energy Budgets and Climate Spaces

Abstract

Heat energy budgets were computed for the American alligator, Alligator mississippiensis, and used to generate steady—state climate space diagrams for large and small individuals. Two sides of the climate space are set by physical characteristics of the environment. The upper and lower limits of the climate space are determined by the size of the alligator, its insulation, metabolic and evaporative water loss rates, heat conducted to the ground, and its maximum and minimum sustainable body temperatures. When the alligator is at its preferred body temperature it is restricted to a small portion of its climate space. This may result in a competitive disadvantage with homeotherms that can maintain a constant internal temperature over a wide range of environmental conditions. Small alligators are more affected by wind speed than large individuals but can tolerate higher temperatures when exposed to full sunlight. Large alligators can operate outside their climate space because they can store large amounts of heat which they dump when they return within their steady—state regimes. Small individuals are closely tied to the limits of their climate space because of their small heat—storage capacity. All sizes of alligators can withstand a wide range of temperatures in a blackbody cavity. Water is the most important part of an alligator's habitat because it acts as a substitute for blackbody conditions and insures maximum utilization of an alligator's potential climate space.If alligators are deprived of water their activity is greatly restricted and their chance of survival is greatly reduced.