Current attempts to study life history evolution have begun to focus on multiple causality: demography, behavior, physiology, biophysics, and ecology all interact to shape life history phenotypes. Emphasis has been placed on evaluating energetic, behavioral, and environmental factors, within a demographic context, in an attempt to generate testable predictions from life history theories. Accordingly, the effects of different soil moisture potentials and temperatures on hatchability, hatchling size (mass and length), and development time in the iguanid lizard, Sceloporus merriami will be evaluated. This will be integrated with the particular pattern of female territoriality and home range use seen in these animals. Females aggressively defend their territories from males and other females, while males direct their defense against other males. Yet for either sex, territories appear to be inherited en bloc. Furthermore, specific territories are "hot spots", where the inhabitants invariably live far longer than the average cohort generation time. Additionally, both large males and large females have more eggs and larger males tend to control more females. Factors affecting size should, then, be important. This integrated approach allows behavior (territoriality), physiology and biophysics (egg requirements), and demography, to be evaluated in an integrated manner with regard to lifetime reproductive success. Any attempt to evaluate minimum areas required to maintain breeding populations of reptiles needs to employ the above multiple causality approach. Such considerations are becoming pivotal to conservation attempts to maintain and restock rare or valuable species. In a very extreme conservation measure, data generated by the above approach can be used to captive-breed decimated populations to use as seed stock in the wild.
