A retrospective analysis of mortality in captive pygmy hippopotamus (Choeropsis liberiensis) from 1912 to 2014

Abstract

The pygmy hippopotamus (Choeropsis liberiensis) is an IUCN Red List Endangered species (CITES Appendix II) that has been housed in zoological collections since 1912. As wild populations continue to decline throughout the species' range, successful ex situ breeding and management, including an understanding of morbidity and mortality, are of utmost importance. This study is the first comprehensive review of mortality data from the captive population since 1982 and significantly expands on previous analyses. We solicited necropsy reports from 129/187 zoological institutions worldwide that currently or previously held pygmy hippos and received data for 404 animals (177 ♂, 220 ♀, 7 undermined sex), representing 43% of pygmy hippos that have died in captivity. Mortality in neonates was primarily due to perinatal causes (51.8%-stillbirth, failure to thrive, weakness, poor suckling reflex, maternal neglect) or parent-inflicted trauma (28%). Common causes of mortality in adult and geriatric animals included cardiovascular disease (16%), degenerative musculoskeletal conditions (10%), obstructive gastrointestinal disease (9%), and renal insufficiency (13%), sometimes associated with advanced polycystic kidney disease (PKD). Although not the direct cause of mortality, a number of adult and geriatric pygmy hippos were also overweight to obese. Infectious causes of mortality in included leptospirosis and encephalomyocarditis virus, the latter usually presenting as acute death due to cardiovascular demise. This comprehensive overview presents a useful guide for recommendations in preventative veterinary care and for improved husbandry and management of pygmy hippos in captivity. Zoo Biol. 35:556-569, 2016. © 2016 Wiley Periodicals, Inc.

Demographics of polycystic kidney disease and captive population viability in pygmy hippopotamus (Choeropsis liberiensis)

“…Figure indicates a high mortality rate for very young animals, especially from birth to 1 year, as previously described by Flacke et al (). One would expect improved survival of zoo‐born neonates and young animals in comparison with wild populations since conditions in captivity remove many of the factors associated with early mortality.…”

“…Results of the survival by sex analyses further illustrate the discrepancy in first‐year mortality between males and females, an ongoing concern for population management. This discrepancy is due to a higher neonatal (0–30 day) mortality rate for male calves (Flacke et al, ) and has been previously noted as contributing to the female‐skewed sex ratio in the captive population (Zschokke, ). Potential underlying mechanisms for the higher male neonatal mortality rate have not yet been explored.…”

“…Even though PKD does not impair reproductive capacity, affected animals still experience significant morbidity and secondary complications, especially in the later stages (Flacke, Tkalčić, Steck, Warren, & Martin ). The clinical significance of this condition in pygmy hippos remains enigmatic, but those with advanced disease develop chronic renal insufficiency based on elevated blood urea nitrogen and creatinine values and clinical signs associated with uremia.…”

A retrospective analysis of mortality in captive Magellanic penguins (Spheniscus magellanicus) in the United States, 2008–2018

“…Although a direct comparison should be made with caution, as it is a report from just one institution regarding a different species of bird, it's interesting to note that similarly high chick mortality has been reported in a closely related penguin species. A high rate of neonatal mortality has been described for birds and other classes of animals in captive settings (Flacke, Tkalcic, Steck, Warren, & Martin, 2016; Kohler, Preston, & Lackey, 2006; Leong, Terrell, & Savage, 2004). The underlying reasons for high chick mortality in captivity are not always known, and, in general, the ultimate cause of mortality may not always be clear.…”

Effects of inbreeding, sex and geographical region on survival in an American bison (Bison bison) population under a captive breeding program

“…Da Rè et al (2018) found considerable effects on survival in mammals housed in zoological gardens. Moreover, unfavorable environmental conditions usually lead to and relatively high mortality (Flacke et al 2016(Flacke et al , 2017.…”