Seasonal Reproductive Cycle of the Desert Tortoise (Gopherus agassizii) in the Eastern Mojave Desert

Abstract

The seasonal reproductive cycles of male and female desert tortoises (Gopherus agassizii) were studied under semi-natural conditions. Tortoises were maintained in outdoor pens subject to ambient weather conditions and received supplemental food and water. Heparinized blood samples were collected monthly using jugular puncture. Ovarian follicular growth and egg development were monitored using ultrasonography. Mating was observed in the fall (following nesting) and the spring (prior to nesting). Vitellogenesis occurred during the fall prior to hibernation. Nesting was observed from May-early July with females producing one or two clutches. Clutches ranged from 2-7 eggs. Both males and females displayed seasonal testosterone cycles.