Effects of Incubation Temperature on Crocodiles and the Evolution of Reptilian Oviparity

Abstract

Crocodylus porosus is a mound-nesting crocodilian in which incubation temperature influences the rate of embryonic development, the probability that embryos will survive to hatching, post-hatching growth rates and the probability of hatchlings surviving to 2 yr of age. Similar responses have been described in Alligator mississippiensis (Joanen et al., 1987) and C. niloticus (Hutton, 1987), and they reflect a suite of "non-sexual" effects of incubation temperature. Temperature-dependent sex determination allocates sex on the basis of these "non-sexual" effects. In C. porosus, it results in maleness being assigned to embryos with high probabilities of surviving and good potential for post-hatching growth. Within the limits of survival, effects of the moisture environment on embryological development rate and hatchling fitness seem minor relative to those of the temperature environment.