Proximate and Evolutionary Constraints on Energy Relations of Reptiles

Abstract

Proximate constraints on the energetics of desert lizards and turtles fall into four major categories: (1) absolute resource availability; (2) harvest rate limitations; (3) process rate limitations; and (4) limitation on harvest or processing resources imposed by risk of predation. Patterns of basking behavior and allocation of resources to reproduction and growth of turtles at high latitudes suggest that ambient air and marsh temperatures combine to regulate the timing and rates of energy processing and allocation. Because reptile eggs contain all of the chemical energy available to developing embryos, interactions between the level of parental investment in each offspring and egg size must, by definition, occur. That portion of the egg material that is invested in the egg but functions as parental care of the hatchling after it leaves the egg functions primarily to affect hatchling quality rather than hatchling size. Therefore, with regard to many reptiles, optimal egg-size models would be more aptly considered to be optimal offspring-quality models.