A Behavioral Inventory of the Desert Tortoise: Development of an Ethogram

A behavioral inventory of the desert tortoise was compiled from observations on confined tortoises in experimental pens and free-ranging tortoises within semi-natural enclosures. We describe 80 actions. Much of a tortoise's active time outside burrows is spent in feeding behavior. Display sequences have both visual and olfactory components. Aggressive and courtship sequences have similar beginnings but proceed differently as animals respond to each other. Aggressive behavior involves much headbobbing, sniffing, biting and ramming. A pushing match enables tortoises to assess body mass and determine dominance. Courtship behavior may involve trailing, circling of the female by the male, and biting and sniffing sequences before mounting. There is no rejection display by females of courting males. Comparisons between Gopherus species and related tortoise groups suggest a very conservative evolution of behavior within the Gopherus group.