<p>Translocation of animals is a widespread tool for resolving human-wildlife conflicts and augmenting struggling wild populations. However, expected time to settlement and survival (both measures of translocation success) are often unknown, particularly as a function of the origin of translocatees. We quantified settling times using Bayesian changepoint detection models on the variance in two derived movement metrics for translocated Mojave desert tortoises (<i>Gopherus agassizii</i>) of two different origins: wild adults and adult waifs (i.e. former pets). We compared the annual home range sizes of translocated tortoises with residents, and we also compared survival of each origin group to tagged resident adults. We found that translocated tortoises from different origin groups took an average of 0.5–2.0 years, depending on origin group, to settle based on movement metrics. Waif tortoises took the longest to settle, on average, within 2 years. There was high individual heterogeneity in settling times among tortoises. Home range sizes were larger for translocated wild tortoises than for resident adults only in the year of translocation. Home range sizes of translocated waif females and males were larger than those of residents, but only for the first two years post-translocation. After accounting for a strong year effect, annual survival rates were not different between resident adults (0.91; 90% CI 0.78–0.98) and translocated wild adults (0.90; 0.67–0.99); survival of waif adults was lower than residents, albeit with overlapping confidence intervals, at an annual rate of 0.80 (0.56–0.95) over the 11-year study. We provide results and discussion of using Bayesian models to identify fundamental changes in the variance of distance from release site and directional movement rate (e.g. erratic versus deliberate movements) to determine translocation success. We also provide guidance for managers of Mojave desert tortoise translocation projects and the translocation of animals in general.</p>

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Origin of translocated animals is associated with time to settlement and post-translocation survival

  • Seth Harju,
  • Scott Cambrin

摘要

Translocation of animals is a widespread tool for resolving human-wildlife conflicts and augmenting struggling wild populations. However, expected time to settlement and survival (both measures of translocation success) are often unknown, particularly as a function of the origin of translocatees. We quantified settling times using Bayesian changepoint detection models on the variance in two derived movement metrics for translocated Mojave desert tortoises (Gopherus agassizii) of two different origins: wild adults and adult waifs (i.e. former pets). We compared the annual home range sizes of translocated tortoises with residents, and we also compared survival of each origin group to tagged resident adults. We found that translocated tortoises from different origin groups took an average of 0.5–2.0 years, depending on origin group, to settle based on movement metrics. Waif tortoises took the longest to settle, on average, within 2 years. There was high individual heterogeneity in settling times among tortoises. Home range sizes were larger for translocated wild tortoises than for resident adults only in the year of translocation. Home range sizes of translocated waif females and males were larger than those of residents, but only for the first two years post-translocation. After accounting for a strong year effect, annual survival rates were not different between resident adults (0.91; 90% CI 0.78–0.98) and translocated wild adults (0.90; 0.67–0.99); survival of waif adults was lower than residents, albeit with overlapping confidence intervals, at an annual rate of 0.80 (0.56–0.95) over the 11-year study. We provide results and discussion of using Bayesian models to identify fundamental changes in the variance of distance from release site and directional movement rate (e.g. erratic versus deliberate movements) to determine translocation success. We also provide guidance for managers of Mojave desert tortoise translocation projects and the translocation of animals in general.