Longevity and Age-Size Relationships of Populations of Desert Tortoises

Abstract

Based on minimum estimates of longevity of desert tortoises (Gopherus agassizii) that died in the field, few individuals live past 50 yr. Approximately 29% of tortoises from the Sonoran Desert, 11% of tortoises from the eastern Mojave Desert, and approx. 5% of tortoises from the western Mojave Desert were estimated to be over 25 yr. The greatest estimate of longevity for any individual was 48-53 yr and came from the eastern Mojave Desert. The oldest individual from the western Mojave Desert was estimated to be 32 yr, and the oldest individual from the Sonoran Desert was estimated to be 35 yr. Comparisons of carapace length to age showed the highest rates of growth (0-25 yr) for tortoises from the western Mojave Desert and Sinaloan habitats. Of the four major regions within the range of the desert tortoise, rates of growth were lowest in the eastern Mojave and Sonoran deserts.