• Consequences of maternal effects on offspring size, growth and survival in the desert tortoise

      Nafus, Melia G.; Todd, B. D.; Buhlmann, K. A.; Tuberville, T. D. (2015)
      Here, we examined the relationship between hatchling and maternal body size in the Mojave Desert tortoise Gopherus agassizii. Our results suggest that, in desert tortoises, maternal body size may indirectly influence offspring fitness via growth and survival for at least the first year of life….
    • Cues from a common predator cause survival-linked behavioral adjustments in Mojave Desert tortoises (Gopherus agassizii)

      Nafus, Melia G.; Germano, Jennifer M.; Swaisgood, Ronald R. (2017)
      Animals are expected to engage in behavioral decision-making that minimizes their risk of predation; these decisions can cause non-lethal predator effects to behavior and spatial use. Our goal was to determine whether non-lethal effects of a common predator, coyotes (Canis latrans), could affect the behavior of a declining reptile, the Mojave Desert tortoise (Gopherus agassizii), hereafter tortoise....
    • Habitat drives dispersal and survival of translocated juvenile desert tortoises

      Nafus, Melia G.; Esque, Todd C.; Averill-Murray, Roy C.; Nussear, Kenneth E.; Swaisgood, Ronald R. (2017)
      In spite of growing reliance on translocations in wildlife conservation, translocation efficacy remains inconsistent. One factor that can contribute to failed translocations is releasing animals into poor-quality or otherwise inadequate habitat. Here, we used a targeted approach to test the relationship of habitat features to post-translocation dispersal and survival of juvenile Mojave desert tortoises Gopherus agassizii. We selected three habitat characteristics – rodent burrows, substrate texture (prevalence and size of rocks) and washes (ephemeral river beds) – that are tied to desert tortoise ecology. At the point of release, we documented rodent burrow abundance, substrate texture and wash presence and analysed their relationship to the maximum dispersal. We also documented the relative use by each individual for each habitat characteristic and analysed their relationships with survival and fatal encounters with a predator in the first year after release. In general, the presence of refugia or other areas that enabled animals to avoid detection, such as burrows and substrate, decreased the overall mortality as well as predator-mediated mortality. The presence of washes and substrate that enhanced the tortoises’ ability to avoid detection also associated with the reduced dispersal away from the release site. These results indicate an important role for all three measured habitat characteristics in driving dispersal, survival or fatal encounters with a predator in the first year after translocation. Synthesis and applications. Resource managers using translocations as a conservation tool should prioritize acquiring data linking habitat to fitness. In particular, for species that depend on avoiding detection, refuges such as burrows and habitat that improved concealment had notable ability to improve the survival and dispersal. Our study on juvenile Mojave desert tortoises showed that refuge availability or the distributions of habitat appropriate for concealment are important considerations for identifying translocation sites for species highly dependent on crypsis, camouflage or other forms of habitat matching.
    • Hiding in plain sight: a study on camouflage and habitat selection in a slow-moving desert herbivore

      Nafus, Melia G.; Germano, Jennifer M.; Perry, Jeanette A.; Todd, Brian D.; Walsh, Allyson; Swaisgood, Ronald R. (2015)
    • Indeterminate growth in desert tortoises

      Nafus, Melia G. (2015)
      ...Using a captive colony of desert tortoises, I explored three questions about adult growth: 1) Do tortoises experience growth at reproductively mature size classes? 2) For those adults that experience growth, is growth continuous throughout adulthood? 3) Are there differences in growth and size between males and females...?
    • Predicting translocation outcomes with personality for desert tortoises

      Germano, Jennifer M.; Nafus, Melia G.; Perry, Jeanette A.; Hall, Derek B.; Swaisgood, Ronald R. (2017)
      As mitigation- and conservation-driven translocations of declining species escalate, establishing best practices for conservation practitioners is critical. A variety of factors, such as individual behaviour, may influence post-release behaviour and survival....