The historical development of juvenile mortality and adult longevity in zoo‐kept carnivores

Abstract

Zoos need to evaluate their aim of high husbandry standards. One way of approaching this is to use the demographic data that has been collected by participating zoos for decades, assessing historical change over time to identify the presence or absence of progress. Using the example of carnivores, with data covering seven decades (1950–2019), 13 carnivore families, and 95 species, we show that juvenile mortality has decreased, and adult longevity increased, over this interval. While no reason for complacency, the results indicate that the commitment of zoos to continuously improve is having measurable consequences.

Linking management practices with survival to improve outcomes for a red wolf population

“…While the causes of mortality have remained consistent over time, age-specific survivorship in the ex situ red wolf population has improved. This finding reflects larger trends of overall survival among zoo-maintained carnivores, where increases in longevity and reductions in mortality rates across age classes can be interpreted as perpetual enhancement of husbandry programs (Roller et al 2021). Our methods for analysis did not sufficiently include relevant variables to test for inbreeding depression, such as a binary measure of survivorship to age of maturity, offspring survival, or lifetime reproductive success (Huisman et al 2016, Farquharson et al 2021.…”

“…Carnivores, generally, are well represented in ex situ breeding and release projects (Seddon et al 2005, Jule et al 2008) but suffer from high neonate and adult mortality (Snyder et al 1996; Clubb and Mason 2003, 2007; Miller et al 2019; Roller et al 2021) and stress‐related behaviors (Mason et al 2007, Clubb and Vickery 2008, Kroshko et al 2016, Miller et al 2019) while under human care. Early mortality and reproductive failures may lead to loss of genetic diversity and excessive stress may render individuals unsuitable for release, thereby impeding reintroduction success (Mason et al 2007).…”

The historical development of zoo elephant survivorship

“…For Asian elephants, first‐year mortalities reported in the literature (1960−2006) are of a magnitude of 40% (Faust et al, 2006; Saragusty et al, 2009), which is higher than our recent finding of 22%. If viewed on its own, and compared to other zoo animals where sometimes distinct changes across decades can be observed (Roller et al, 2021), juvenile mortality might be considered stable in zoo elephants. With the transition to protected contact and an increase in more natural births in female groups rather than by isolated individuals, the establishment of matrilines skilled in giving birth support may still take some time (Prahl, 2009).…”

“…In the experience of one of the coauthors (L. B. L.), the practice of not entering newborn animals until they survived to about 1 month of age was more common in earlier decades of the last century than it is now. This would result in an underestimation of positive developments in neonate mortality (Roller et al, 2021). The same might apply for stillbirths.…”

“…For different nondomestic species, a historical improvement of zoo survivorship has been documented, including orangutans ( Pongo sp.) (Wich et al, 2009), orcas ( Orcinus orca ) (Jett & Ventre, 2015), bottlenose dolphins ( Tursiops truncatus ) (Jaakkola & Willis, 2019) or chimpanzees ( Pan troglodytes ) (Havercamp et al, 2019), and many members of the Carnivora (Roller et al, 2021). Irrespective of the question how far off zoos may (or may not) be from a specific benchmark, the question whether zoos are making progress in the husbandry of a species, in terms of improving in the measure under investigation, is also a crucial one.…”