INCUBATION-TEMPERATURE AFFECTS BODY-SIZE AND ENERGY RESERVES OF HATCHLING AMERICAN ALLIGATORS (ALLIGATOR-MISSISSIPPIENSIS)

Incubation temperature determines sex in crocodilians and influences other features of hatchlings. We investigated the effects of incubation temperature, clutch, and sex on the dimensions, mass, and energy reserves of hatchling Alligator mississippiensis. Eggs from three clutches were incubated to pipping at constant temperatures of 29 degrees, 31 degrees, 32 degrees, and 33 degrees C; females were produced at 29 degrees and 31 degrees C, mixed sex ratios at 32 degrees C, and males at 33 degrees C. Incubation temperature affects hatchling size and yolk utilization in a consistent, but complex, pattern. Maximum yolk-free hatchling mass occurred at 32 degrees C, and minimum mass at 31 degrees C. Similarly, dimensions were maximized at 32 degrees C and minimized at 29 degrees C. Residual yolk mass was inversely related to yolk-free hatchling mass Higher yolk mass occurred at 31 degrees and 33 degrees C; at 29 degrees and 32 degrees C, values were lower. However Sat mass remained constant in all clutches. Strong clutch effects were present in nearly all traits. At 32 degrees C, males were heavier and had less yolk than females. These differential effects of incubation temperature, and consequently sex, affect important hatchling characteristics and may influence hatchling survival and fitness, in accord with recent theory.