Survivorship and Predation of Hatchling and Yearling Gopher Tortoises, Gopherus polyphemus

Abstract

Gopher tortoise (Gopherus polyphemus) populations have declined as much as 80% over the past century, and the major source of this decline is habitat loss linked to human activities such as urbanization, agriculture, and mining (Auffenberg and Franz, 1982; Diemer, 1986). As tortoise populations become more restricted due to these factors, what previously may have been natural or sustainable mortality may now be more devastating. Predation on adult gopher tortoises by feral dogs was reported by Causey and Cude (1978), but adult tortoises have few predators besides humans (Auffenberg and Iverson, 1979). Mortality of eggs and hatchlings, however, has been estimated at greater than 90% (Alford, 1980; Landers et al., 1980; Witz et al., 1992). Predators of hatchlings and juveniles have been reported as avian (Fitzpatrick and Woolfenden, 1978; Wilson, 1991; Smith, 1996), mammalian (Wright, 1982; Wilson, 1991; Smith, 1996), snakes (Douglass and Winegarner, 1977), and ants (Landers et al., 1980; Smith, 1996). The goals of this study were to record daily survivorship of free-ranging hatchling gopher tortoises (those surviving beyond a year are referred