Review of hyperdispersal in wildlife translocations

Abstract

Species translocation is a common tool to reverse biodiversity loss, but it has a high failure rate. One factor that contributes to failure is postrelease hyperdispersal, which we define as the long‐distance movement of individuals resulting in their failure to contribute to population establishment. We reviewed reported incidences of hyperdispersal and compared rates of hyperdispersal among taxa, population demographics, release cohorts, and success of mitigation techniques. Of 151 conservation translocations (reinforcements and reintroductions) in which animals were tracked, hyperdispersal was confirmed in 52.1% of programs. The prevalence of hyperdispersal (percentage of studies) was relatively consistent across taxa (42.9–60%), but hyperdispersal rates in birds were likely underestimated because 76.9% of bird translocations showed incidences in which birds could not be located after release, but hyperdispersal was unable to be confirmed. Eutherians exhibited a higher average incidence of hyperdispersal (percentage of hyperdispersing individuals in a cohort) of 20.2% than birds, reptiles, and marsupials (10.4%, 15.7%, and 10.3%, respectively). No significant trends were observed for sex, source population, or translocation type, but there were nonsignificant trends for males to hyperdisperse more than females and for higher incidences of hyperdispersal in reinforcements relative to reintroduction programs. Mitigation techniques included temporary confinement, supplementation of resources, and releasing animals in social groups, but only half of studies examining mitigation techniques found them useful. Hyperdispersal incidence was variable within taxa, and we advise against forming translocations strategies based on results from other species. Hyperdispersal is a significant welfare, economic, and conservation issue in translocations, and we suggest definitions, reporting, and experimental strategies to address it.

Are subadult dispersers at high risk of mortality in translocated populations? A case study from a threatened mesopredator

“…For populations that have been translocated into new areas, natal dispersal may be particularly risky. Subadults moving into unoccupied habitat will not benefit from conspecific cues alerting them to suitable habitat and thus may disperse into unknown habitat and outside of areas under intensive management (Bilby & Moseby, 2023; Stamps & Swaisgood, 2007). Disturbances from habitat fragmentation, physical barriers, and increased mortality during dispersal are likely to lead to reduced gene flow and inbreeding within a population (Banks et al., 2005; Frankham et al., 2014; Levy et al., 2013) which may also affect the long term sustainability of reintroduced populations.…”

Extreme temperatures impede the release success of captive-bred avian scavengers

“…Post-release movements can determine the survival of translocated animals by shaping how they acquire information or encounter risks. Exploratory movements are very common in many taxa (Gouar et al, 2008a;Linklater & Swaisgood 2008;Pinter-Wollman 2009;Marques et al, 2011;Nussear et al, 2012;Pille et al, 2018;Griffith et al, 2019;Bilby & Moseby 2023). However, some animals remain in the vicinity of the introduction area post-translocation (Nafus et al, 2017;Garnier et al, 2021).…”

Identifying Conservation Introduction Sites for Endangered Birds through the Integration of Lidar-Based Habitat Suitability Models and Population Viability Analyses

“…A major challenge in achieving successful CI arises from an incompatible habitat at the release site compared with the habitat of origin [18,19]. A global review of CI success found that habitat-related factors were the largest drivers of initial declines for birds and other taxa released in novel habitats [2].…”