An integrated approach for assessing translocation as an effective conservation tool for Hawaiian monk seals

Abstract

For threatened and endangered species, translocations have been widely used to mitigate multiple sources of mortality that threaten population recovery. Although numerous Hawaiian monk seals Neomonachus schauinslandi have been translocated for a variety of purposes, few monk seal translocations have addressed the problem of prey limitation. To assess the efficacy of using translocations to mitigate reduced prey availability, 12 weanling monk seals were translocated with pre-release health screening and post-release monitoring. Specifically, the health, foraging behavior, habitat use, and survival of translocated seals were compared with those of 17 monk seals resident to the release site. There was little evidence of infectious diseases in translocated and resident seals, although Chlamydophila abortus antibodies and enteric bacteria were detected in many individuals. Translocated and resident weanling seals also demonstrated similar diving, movements, and habitat use, whereas resident adult seals had greater variability in foraging patterns. First-year survival for translocated weanlings (50%, n = 12) and non-translocated weanlings at the donor (31%, n = 36) and recipient sites (69%, n = 16) was related to weaning body size, with larger individuals having greater survivorship. These results supported 3 main conclusions that have important consequences for future translocation and population recovery efforts: (1) there was minimal risk of exposing seals to novel infectious diseases as a result of translocation; (2) individuals translocated with limited foraging experience rapidly adapted to their post-release environment; and (3) translocation for the purpose of mitigating prey limitation is a viable and important conservation tool for Hawaiian monk seals.

A field effort to capture critically endangered vaquitas Phocoena sinus for protection from entanglement in illegal gillnets

“…Short-term ex situ methods, without captive propagation, have been applied to other marine mammals, with the translocation and/or release of individuals temporarily removed from the wild. For example, human intervention has led to increased survival of endangered Hawaiian monk seals Neomonachus schauinslandi, with as much as a third of the population benefitting from such efforts (Harting et al 2014, Norris et al 2017. One major challenge with implementing an ex situ approach with the vaquita is that experience with releasing cetaceans from human care is minimal.…”

Modest immigration can rescue a reintroduced carnivore population

“…Periodic translocations have been implemented for a number of carnivores in the United States (Wisely et al ) and Europe (Simón et al ). Such repeated translocations can increase survivorship (Norris et al ) and the number of reproductive adults (Marino et al ), and enhance short‐term population growth (Kinley and Newhouse ). However, such benefits are not guaranteed, and some translocations fail to enhance reproductive output (Manlick et al ) or population size (Hayward et al ).…”

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

“…Faced with this grim situation, an experiment was conducted to evaluate whether conservation translocations from a subpopulation with low juvenile survival to a site where survival prospects were likely better might be an effective tool to mitigate early mortality. Thus, in 2008Thus, in -2009, a total of 12 weaned pups was removed from French Frigate Shoals (where juvenile survival was especially poor) and released at Nihoa Island at the eastern end of the NWHI (Norris et al, 2017). Nihoa was chosen as the destination for the translocation experiment because recent increasing trends in index counts of seals at this site suggested that juvenile survival was likely favorable (Harting, Baker & Johanos, 2017).…”

“…Nihoa was chosen as the destination for the translocation experiment because recent increasing trends in index counts of seals at this site suggested that juvenile survival was likely favorable (Harting, Baker & Johanos, 2017). Norris et al (2017) compared translocated and resident Nihoa Island seals' clinical health status, disease exposure, foraging behavior and habitat use. However, results regarding post-release survival of translocatees relative to seals remaining at French Frigate Shoals and residents at Nihoa were inconclusive for two reasons.…”

“…As it happened, translocated pups were fatter on average than those remaining at French Frigate Shoals and comparable in girth to Nihoa resident pups. Norris et al (2017) found that girth was the only significant predictor of minimum survival rates, such that whether the survival of translocated seals was enhanced remained uncertain. Despite the inconclusive results regarding survival benefits, Norris et al (2017) demonstrated that translocations of weaned monk seal pups between subpopulations could be safely conducted and that translocated pups adapted well to their new home and developed normal foraging behavior.…”