Incubation Temperature Affects Body Size and Energy Reserves of Hatchling American Alligators (Alligator mississippiensis)

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Abstract
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°, 31°, 32°, and 33° C; females were produced at 29° and 31° C, mixed sex ratios at 32° C, and males at 33° C Incubation temperature affects hatchling size and yolk utilization in a consistent, but complex, pattern. Maximum yolk-free hatchling mass occurred at 32° C, and minimum mass at 31° C. Similarly, dimensions were maximized at 32° C and minimized at 29° C Residual yolk mass was inversely related to yolk-free hatchling mass. Higher yolk mass occurred at 31° and 33° C; at 29° and 32° C, values were lower. However, fat mass remained constant in all clutches. Strong clutch effects were present in nearly all traits. At 32° 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.

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