Why Do Captive Lions Die Young?

Lions used to be broad ranging animals that lived across parts of Europe, Africa, the Middle East and Asia, but they are now endangered with an estimated 32,000 to 35,000 free ranging lions in Africa and only 350 left in Asia. Conservation efforts include breeding programs at zoos. But while lions “reproduce well” in captivity, mortality rates among young, captive bred lions are high. For example, a 2002 study found that of 126 captive-born lions, 40.5% died before reaching two years of age. The cause of death ranged from infanticide to stillbirth, but a startling 74.5% died of unknown causes. Similar numbers have been reported in other studies, which has lead to great concern about captive breeding.

This study considers whether bone malformations may be a leading cause of captive lion death, and it makes a good if tentative case based on the available data. Skull abnormalities have been reported in captive lions from as far back as the fifteenth century. In more recent times, they’ve been reported in captive lions at zoos in Europe, South Africa, Australia, the U.S., and Asia. The authors are careful to note that it’s not known whether the cause of these malformations is environmental or genetic (or both). However, such abnormalities haven’t been found in wild populations to date. The study authors compared the skulls of lions who died in the wild with skulls from captive lions kept at natural history museums on three continents. They found that 40.4% of the captive lion skulls showed abnormalities; only 4.2% of the wild lion skulls showed similar abnormalities.

The researchers note that their study could be enriched by gathering more specific habitat data on captive lions. They also point out that it’s still unclear whether the skull abnormalities are the result of nutritional defects or other environmental factors. However, the findings from this study demonstrate one of many ways in which captive environments may jeopardize lions’ welfare.