Translocation as a conservation tool for Agassiz's desert tortoises: Survivorship, reproduction, and movements

Abstract

We translocated 120 Agassiz's desert tortoises to 5 sites in Nevada and Utah to evaluate the effects of translocation on tortoise survivorship, reproduction, and habitat use. Translocation sites included several elevations, and extended to sites with vegetation assemblages not typically associated with desert tortoises in order to explore the possibility of moving animals to upper elevation areas. We measured survivorship, reproduction, and movements of translocated and resident animals at each site. Survivorship was not significantly different between translocated and resident animals within and among sites, and survivorship was greater overall during non‐drought years. The number of eggs produced by tortoises was similar for translocated and resident females, but differed among sites. Animals translocated to atypical habitat generally moved until they reached vegetation communities more typical of desert tortoise habitat. Even within typical tortoise habitat, tortoises tended to move greater distances in the first year after translocation than did residents, but their movements in the second or third year after translocation were indistinguishable from those of resident tortoises. Our data show that tortoises translocated into typical Mojave desert scrub habitats perform well; however, the large first‐year movements of translocated tortoises have important management implications. Projects that employ translocations must consider how much area will be needed to contain translocated tortoises and whether roads need fencing to prevent the loss of animals. © 2012 The Wildlife Society.

Mitigation-driven translocation effects on temperature, condition, growth, and mortality of Mojave desert tortoise ( Gopherus agassizii ) in the face of solar energy development

“…For short-distance translocations, we observed short-term thermal effects primarily in the first month but no differences in condition, growth or mortality for translocated tortoises. Several authors have suggested translocation of desert tortoises may serve as a conservation or mitigation tool (Drake et al, 2012;Field et al, 2007;Nussear et al, 2012), and given the lack of group effects on condition, growth, or mortality, our study supports these previous findings.…”

“…The relatively short-term thermal effects may have been ameliorated, in part, by tortoise familiarity with cover site locations or because tortoises were released with time to find or construct burrows during cooler environmental temperatures in spring (Henen, 1997;Nussear et al, 2012). Even highest translocated tortoise temperatures in the first month were within the range of variation for all groups later in the active season.…”

“…These studies have found no effect of translocation compared with resident or control populations on survivorship or mortality (Esque et al, 2010;Field et al, 2007;Nussear et al, 2012), stress (Drake et al, 2012), or reproductive output . Increased movement has been the largest effect observed in both long-distance (Field et al, 2007;Nussear et al, 2012) and short-distance (Farnsworth et al, 2015;Hinderle et al, 2015) translocations. For short-distance translocations, we observed short-term thermal effects primarily in the first month but no differences in condition, growth or mortality for translocated tortoises.…”

“…Prior studies indicated tortoise movements increased initially post-translocation, after which tortoises established home ranges, movement behavior, or space-use indistinguishable from control tortoises (Farnsworth et al, 2015;Field et al, 2007;Nussear et al, 2012). Increased movement was likely due to either homing to familiar areas (Hinderle et al, 2015) or questing after shelter, food, or mates in unfamiliar areas, and Sullivan et al (2015) suggested translocations have a low success rate when judged by increased movement.…”

“…A few studies have addressed the effects of translocation on this threatened reptile (Drake et al, 2012;Esque et al, 2010;Field et al, 2007;Hinderle et al, 2015;Nussear et al, 2012), but only one has addressed mitigation-driven translocation effects on desert tortoises following utility-scale solar development (Farnsworth et al, 2015). Prior studies indicated tortoise movements increased initially post-translocation, after which tortoises established home ranges, movement behavior, or space-use indistinguishable from control tortoises (Farnsworth et al, 2015;Field et al, 2007;Nussear et al, 2012).…”