Planet Earth

Zoo elephants die much earlier than wild ones

Not Exactly Rocket ScienceBy Ed YongDec 12, 2008 7:30 PM


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Elephants always count as star attractions in any zoo or wildlife park lucky enough to have them. But while many visitors may thrill to see such majestic creatures in the flesh, some scientists have raised concerns about how well animals so sociable and intelligent would fare in even the best of zoo environments.

Now, a new study suggests that some of these concerns might be warranted. Ros Clubb from the RSPCA, together with colleagues from various universities and the Zoological Society of London, studied the health of zoo elephants with a census of mammoth proportions.

Concentrating on females, she surveyed 786 captive elephants, representing about half the total zoo population. She compared them to about 3,000 individuals who either live wild in protected Amboseli National Park in Kenya or who are employed by the Burmese logging industry.

The survey revealed incredible differences in the life spans between the captive and wild creatures. On average, African elephants in Amboseli live for about 56 years, while those born in zoos lasted a mere 17 years. Even wild elephants that were killed by humans managed a good 36 years of life. These grim statistics were due to adult females dying much earlier - the death rates among Infant and juvenile individuals were the same in both wild and captive populations.

For Asian elephants, the picture was similar. Those that worked in natural environments for the Burmese logging industry lived longer, averaging a lifespan of 42 years, compared to a figure of just 19 of their zoo-born peers. In their case, infant deaths accounted for much of the difference made a massive difference and the death rate was twice as high among newborns at the zoo than in those in Burma.

Clubb thinks that the low infant survival among zoo-born Asian elephants is due to very early events in their lives, possibly even before they leave their mothers' wombs. Indeed, even elephants that are captured from the wild (usually at the age of 3-4 years) have higher life expectancies than those born to captivity.

Things have certainly improved. Clubb found that in recent years, the lifespan of zoo elephants had increased, but their odds of dying early were still about 3 times higher than those of their wild cousins. And the poor infant death rates for Asian elephants hadn't improved. Asian elephants are also sensitive to being shuttled around between zoos, particularly if calves are separated from mothers, and such transfers can affect their health up to four years later.

Clubb points the finger at stress and obesity as the main factors behind the earlier demise of zoo elephants. The problems highlighted in this survey back up a large amount of anecdotal evidence. In 2002, the RSPCA conducted a review of European zoo elephants, which found worrying rates of herpes, tuberculosis, lameness and infertility and of adults killing calves. And zookeepers are well aware that, unlike many other animals, elephants cannot be kept in captivity with enough success to create self-sustaining populations - new individuals need to be brought in from elsewhere.

If this new study is to be believed (and it will undoubtedly provoke strong responses from zoos), the biggest remaining question is whether the benefits to keeping elephants in zoos, in terms of both education and conservation, are large enough to justify the costs that such homes could exert on their health? It would also be interesting to see a deeper study looking at the extent to which the quality of a zoo affect an elephant's lifespan. Put simply, there are zoos and then there are zoos.

Reference: Science 10.1126/science.1164298

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