Reproductive biology

Courtship usually includes the male chasing the female, often head bobbing, biting at her extremities, and/or ramming

Giant tortoises (Geochelone nigra vandenburghi) gathering in a seasonal rain pond on the caldera floor of Alcedo Volcano, Isabela Island, Galápagos. (Photo by Tui De Roy. Bruce Coleman, Inc. Reproduced by permission.)

her shell with his. Eggs are brittle-shelled, spherical to elongate, typically measuring 1-2 in (3-6 cm) in greatest diameter. Clutch sizes are generally small, ranging from one to 51 eggs per clutch, and are generally related to female size. Multiple clutches in one season are produced by many species, although some females apparently do not reproduce every year. Incubation is typically 100-160 days and is reported to last as long as 18 months in one species. Although most species have not been studied, those that have exhibit temperature-dependent sex determination, with females produced at high incubation temperatures and males at low temperatures.

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