Physiological Ecology of Desert Iguana (Dipsosaurus Dorsalis) Eggs: Temperature and Water Relations

The soil environment imposes constraints on the timing of oviposition and the location of suitable sites for egg burrows of the desert iguana (Dipsosaurus dorsalis). The effects of temperature and water potential on the developmental period and hatching success of eggs were determined. Eggs hatch normally between 28° and 38°C at environmental water potentials between —50 and —1500 kPa. Predictions were derived for the timing and placement of egg clutches based on soil water potential and temperature profiles measures in the field and on the results of laboratory incubation experiments. The results suggest that egg burrows should be located at depths >22 cm in washes or possibly in sparsely vegetated areas away from creosote bushes. The biogeography of desert iguanas within the United States is discussed in relation to soil environments and tolerances of eggs. The physical factors affecting incubation may limit the geographical range of desert iguanas.