Balancing conservation and welfare in ex situ management of the extinct-in-the-wild sihek: sex- and age-specific causes of mortality and contributions to population growth rate

Ex situ threatened species management has both conservation and welfare objectives and these objectives often align, but can diverge. Areas of agreement can present win-wins for achieving welfare and conservation objectives, while identifying areas of divergence is important to ensure management strategies achieve balance across objectives. We examined welfare and conservation objectives in the ex situ population of Extinct in the Wild sihek (Guam kingfisher, Todiramphus cinnamominus) by quantifying mortality rates, determining sex- and age-specific causes of mortality and identifying associated welfare domains, as well as quantifying sex- and age-specific differences in reproductive value and contributions to variation in population growth rate (λ). Females had significantly higher mortality rates than males, potentially impacting population viability and suggesting females may be more vulnerable to experiencing lower welfare than males. Mitigating causes of female mortality would therefore present a clear win-win for both welfare and conservation objectives. Both causes of mortality and contributions to variation in λ were found to differ across sex- and age-classes. In particular, nutritional and metabolic diseases tended to impact younger age-classes and these age-classes had large contributions to variation in λ. Mitigation of these diseases could therefore also present a win-win for welfare and conservation objectives. However, we also identified a potential divergence between objectives: a major cause of female mortality was reproductive disease with older aged females primarily affected, but older aged females contributed little to variation in λ and had low reproductive value. Developing mitigation strategies for reproductive disease could therefore aid welfare objectives but have little benefit for conservation objectives, suggesting careful balancing across objectives is required. Our results highlight the need to explicitly consider conservation and welfare objectives in threatened species management, in particular in the context of an increasing conservation need for ex situ population management, coupled with increasing social concern for animal welfare.