Desert tortoise (Gopherus agassizii) (Photo: USFWS)

Kim Field (center) with volunteers and collaborators at a field site in southern Nevada. (Photo: USFWS)

Jeannie Stafford, Nevada FWO   

Kim Field, Regional Desert Tortoise Recovery Coordinator at the Nevada Fish and Wildlife Office (FWO) presented an overview of elements that will form the basis of a new desert tortoise population augmentation strategy at the First International Wildlife Reintroduction Conference, April 15-17, 2008, in Chicago.  Kim’s presentation included her own original research and described how her studies and other research are being used to revise the desert tortoise plan into a strategic, research-based program to augment depleted populations of the tortoise.

Kim was one of 31international scientists invited to present at the conference by the International Union for Conservation of Nature (IUCN) Species Survival Commission (SSC) Reintroduction Specialist Group and Lincoln Park Zoo.  The international wildlife conference focused on the evolving field of reintroduction science.  Top experts in the field presented “lessons learned” from past reintroductions and identified scientific processes that improve effectiveness, promote multiple approaches to the science of reintroduction, and build a culture of innovative theoretical and applied research on reintroductions.

A key element of the draft revised desert tortoise recovery plan is “population augmentation.” The goals of such a program are to maintain tortoise populations in wild for continued study of threats and effectiveness of conservation actions and to hasten recovery of decimated or extirpated populations following removal of threats.

The Desert Tortoise Recovery Office at the Nevada FWO plans to develop a strategic program for augmenting desert tortoise populations by drawing from recent research into translocation of adult tortoises, head-starting of juvenile tortoises, disease, and genetics across the range of the tortoise.  Translocation of adult tortoises has shown some initial successes, including similar survival and reproduction compared to wild resident tortoises, typical home ranges established by second season, and appropriate foraging, shelter seeking, and mating behaviors observed.

Recent head-starting studies have taken eggs from gravid wild females, hatched them in large semi-natural enclosures, and provided supplemental water to increase food plants for the hatchlings and juveniles.  Preliminary results have shown increased hatching success, increased first-year survival, and juveniles with more food plants available grow 3 times faster; researchers are currently following juveniles released at different ages and sizes.

Disease issues must also be considered, so the Desert Tortoise Recovery Office’s Science Advisory Committee has developed pertinent guidelines specific to the release of animals to the wild. Several factors or available information also must be considered in identifying potential release sites, including a new habitat model, results from the range-wide monitoring effort, genetics, conservation actions in place at the release site, and opportunities to implement new actions and learn about effects.