Water balance of the eggs of a desert lizard (Callisaurus draconoides)

Abstract

Eggs of a desert lizard (Callisaurus draconoides) were incubated under hydric conditions simulating those of natural nests. Eggs increased in mass during the first half of incubation owing to a net uptake of water, and declined in mass during the second half of incubation owing to a net loss of water. Patterns of net water exchange were related to water potential of substrates on which eggs were incubated, and could be modified by increasing the proportion of each eggshell contacting the substrate. Hatching success was high among eggs associated with wetter substrates but very low for eggs incubated on drier substrates. Eggs associated with wetter substrates also had longer periods of incubation and gave rise to larger hatchlings than eggs exposed to drier substrates. These findings indicate that nest-site selection by females is an important determinant of reproductive success, for selection of appropriate nesting sites increases the probability of high hatching success and of young lizards attaining large size prior to hatching.