Identifying temporal dynamics in post‐release survival of a restored large ungulate

Abstract

Abstract Wildlife translocation is an important conservation tool for restoring species and reducing global biodiversity decline; however, this practice is challenging for wildlife, and translocated individuals must adjust to their release landscapes for restoration success. The period following release is a vulnerable time for wildlife and determining when animals acclimate following translocation improves long‐term estimates of population dynamics and allows researchers to efficiently tailor translocation design and post‐release management to each population's needs. We evaluated demographic acclimation and investigated changes in post‐release survival of a population of 106 elk Cervus canadensis translocated to Missouri, USA, in 2011–2013 using generalized survival modelling. We defined the acclimation period as the duration of time prior to stabilization in mortality risk relative to time from release, and we evaluated acclimation duration from flexible plots of estimated mortality hazards across time. We simultaneously investigated factors contributing to post‐release survival and compared survival rates and mortality sources observed during acclimation and post‐acclimation periods. Elevated mortality risk for translocated elk spanned a 5‐month acclimation period following release, with an additional 1‐year period reflecting reduced, but still elevated, mortality hazards. Baseline hazards during the initial 5‐month acclimation period were approximately four times higher than the subsequent 4.4 years following release. Release cohort, but not age class or sex, was associated with post‐release mortality risk, and mortality sources within the acclimation period tended to be undetermined with greater frequency relative to mortalities occurring after the acclimation period. Our results highlight the utility of flexible modelling approaches to evaluate dynamic post‐release responses of translocated populations. Translocated elk demonstrated a pronounced demographic acclimation period that spanned 5 months following release. Changes in mortality sources and the timing of stabilization in mortality hazards suggest that demographic acclimation in translocated elk was associated with adjustments in physiological stress and movement rates which stabilized over a similar post‐release duration. Improving post‐release monitoring and assessment of restored populations by evaluating temporal dynamics of manifold biological and ecological responses as translocated animals acclimate to their new landscapes is vital to successful restoration efforts.