Influence of the Hydric and Thermal Environments on Eggs and Hatchlings of Bull Snakes Pituophis melanoleucus

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Abstract
Eggs of bull snakes (Pituophis melanoleucus) were incubated at temperatures of 22.0, 27.0, and 32.0 C on substrates with water potentials of -150, -300, and -1,100 kPa using a 3 X 3 factorial design. The thermal and hydric environments affect fluxes in water between eggs and their surroundings during the course of incubation. Eggs incubated at low temperature (22.0 C) and on wet substrate (-150 kPa) gain the greatest amount of mass during incubation, while eggs incubated at high temperature (32.0 C) on dry substrate (-1100 kPa) lose the greatest amount of mass. The proportion of eggs that hatch is lower at the low temperature, while incubation at the high temperature results in a greater proportion of hatchlings with abnormalities. In general, eggs incubated at the intermediate temperature produce larger hatchlings than do eggs held at either low or high temperatures. While the hydric environment does not affect hatching success, eggs exposed to wet or moist hydric conditions give rise to larger hatchlings than do eggs exposed to dry conditions. Both temperature and water availability affect the composition of hatchlings.