Causes of mortality in sloth bears (Melursus ursinus) housed in U.S. zoos

Abstract

A retrospective mortality review was performed of necropsy records from 1905-2015 to determine the mortality trends present for the captive U.S. sloth bear (Melursus ursinus) population.  Records were obtained for 68 bears from 17 institutions.  Neonates had an average age at death of 7 days (median 0 days).  Neonatal mortality accounted for a significant proportion of reviewed cases (29.4%) and was most often due to stillbirth and infectious disease.  Juvenile mortality was uncommon (2.9%).  The average age at death for adult bears was 16.7 yr, with females surviving a few years longer than males.  Biliary adenocarcinoma was the leading cause of death for adult bears (58.7-65.2%) with no apparent gender predilection.  Possible causative factors for the high frequency of biliary adenocarcinoma in sloth bears are proposed and compared to other species including humans.