Behavioral and Morphological Adaptations by Galapagos Land Iguanas (Conolophus subcristatus) to Water and Energy Requirements of Eggs and Neonates

Abstract

We examine the importance of both the hydric environment of naturally incubating reptilian eggs and the energetic needs of hatchlings via an investigation of reproduction in Galapagos land iguanas ( Conolophus subcristatus ). Hatching success of egg clutches and the size of subsequent hatchlings are both positively correlated with the water potential of natural nests, as predicted from previous laboratory experiments. Water potentials representing optimal incubation environments are available for only a brief period in nature, and depend upon the same seasonal rainfall as does food abundance for the emerging hatchlings. The temporal placement of the reproductive season of Conolophus subcristatus balances these conflicting needs for water by eggs and energy by hatchlings. Oviposition occurs slightly before suitable water potentials are reached and hatchling emergence occurs after the peak in food abundance. Morphological adaptations by Conolophus subcristatus to their precarious reproductive phenology include greater amounts of albumen in their eggs, and greater energy reserves in emergent hatchlings than most other lizard species. These adaptations lessen the severity of an arid environment where water becomes available for periods too short to allow both oviposition and hatching to be temporally placed in an optimal manner.