Conservation translocations of Hawaiian monk seals: accounting for variability in body condition improves evaluation of translocation efficacy

Abstract

AbstractTo assess the efficacy of conservation translocations, survival of released individuals is typically compared to that of control groups. Such comparisons assume that treatment groups consist of otherwise equivalent individuals. When that assumption is unmet, incorporating physiological parameters may improve assessment of translocation programs. During 2012–2014, 19 weaned female Hawaiian monk seal pups were translocated to sites where survival prospects were expected to be more favorable than at their natal locations. We compared survival from weaning to age two years of translocated pups to two control groups; pups remaining at source sites and pups native to destination sites. To account for the known relationship between weaning girth and survival, we generated probability distributions of the number of survivors at source and destination sites given the weaning girths of translocated seals. Data were available to calculate girth‐adjusted survival probabilities for 13 of the translocated pups. Of these, we estimated that only one pup would have been expected to have survived had the translocated pups remained at their natal site. Seven of the 13 translocated seals survived, a value just below the median (eight) expected to have survived at the destination site. Thus, translocation substantially improved survival. Had we not accounted for weaning girth effects on survival, we would have erroneously concluded that the translocation program had yielded no survival benefit. Identifying and integrating correlates of survival into quantitative analyses associated with conservation translocations can reduce bias and lead to greater success.