Assessing zoo giraffe survivorship: Methodological aspects, historical improvement and a rapid demographic shift

Abstract

Giraffe have been kept in zoos for a long time. They have traditionally been considered difficult to maintain due to various husbandry requirements, including their nature as intrinsic browsers. However, zoo animals are expected to achieve higher survivorship than free-ranging conspecifics due to protection against dangers that would be experienced in their natural habitat. Global zoo giraffe data was analysed for historical developments of juvenile and adult survivorship, assessing the data with various demographic measures and comparing it to that of populations from natural habitats. Additionally, zoo population structure was analysed, in particular with respect to two events that occurred in parallel in 2014—a recommendation to restrict the number of new offspring given by the European Endangered Species Programme (EEP) studbook coordinator and the culling of a designated ‘surplus’ giraffe at Copenhagen Zoo that attracted global media attention. Both juvenile and adult giraffe survivorship has increased over time, suggesting advances in giraffe husbandry. For juveniles, this process has been continuous, whereas for adults the major progress has been in the most recent cohort (from 2000 onwards), in parallel with the publication of various husbandry guidelines. Zoo giraffe survivorship is now generally above that observed in natural habitats. Simple survivorship analyses appear suitable to describe these developments. Since 2014, the global giraffe population has undergone a rapid demographic shift from a growing to an ageing population, indicating a drastic limitation of reproduction rather than a system where reproduction is allowed and selected animals are killed (and possibly fed to carnivores). Thus, giraffe are both a showcase example for the historical progress made in zoo animal husbandry due to efforts of the zoo community and serve as an example to discuss implications of different methods of zoo population management.