Escaping senescence: demographic data from the three-toed box turtle (Terrapene carolina triunguis).

Two criteria have been proposed for the demonstration of negligible senescence. These include (1) no increase in age-related mortality and (2) negligible functional impairments with age. Although researchers have suspected turtles to exhibit negligible senescence, this has been largely based on the former rather than the latter criteria for which scant evidence is available. Using a long-term study on a population of three-toed box turtles (Terrapene carolina triunguis) in Cole County, Missouri, I combine known minimum age ranges and reproductive evidence to demonstrate their apparent escape from senescence. During 1998 and 1999, eight females >60 years of age were found gravid. The oldest of these is estimated to be at least 65-74 years of age. Of females >60 years, the mean clutch size and the proportion gravid were greater, although not significantly different, when compared to females <60 years. These findings indicate that the reproductive function in these turtles does not become impaired with age, thus supporting the second criteria for demonstrating negligible senescence.