VARIATION IN HATCHLING TORTOISE SURVIVORSHIP AT THREE GEOGRAPHIC LOCALITIES Available to Purchase

Survivorship of hatchling chelonians is low in many instances, although few investigators have intensively studied the immature life stages. We used radio telemetry to assess hatchling gopher tortoise (Gopherus polyphemus) survivorship in central Florida (n = 20), and compare our results to previously published studies in north Florida and Mississippi. At our site tortoise predation was extremely high, and no hatchlings lived over 335 days. Average lifespan was consistent among clutches, and the highest mortality occurred within one month of hatching. Major predators included mammals and snakes. Our results are similar to published data from north Florida (n = 20) and Mississippi (n = 45), although hatchlings in north Florida survived the longest. However, all tortoises (n = 85) in each study died many years before reaching sexual maturity due to predation. Hatchling predators varied by site, but mammals were the major predator at all three sites. We discuss the population-level consequences of high mortality in the younger life stages and several hypotheses associated with population stability. Although hatchling mortality was extremely high, long-term data from our central Florida site show that immature animals are captured on a regular basis. The most likely explanation for this apparent contradiction is that true hatchling survival levels are above zero, but are too low to be accurately detected with the current sample sizes. Therefore, long-term mark-recapture studies focusing on hatchling and juvenile animals are necessary to determine whether recruitment is sufficient to maintain current population sizes, or if populations are declining slowly.