For African elephants, the median life span is 17 years for zoo-born females, compared to 56 years in the Amboseli National Park population.
For Asian elephants, the results are "much more worrying because they are the rarer of the two species," Mason said.
Zoo females only live 19 years—about half the life span of the Myanma timber elephants, which, on average, survive until 42.
What's more, the team discovered that Asian elephants bred and born in captivity died earlier than those imported into zoos from the wild.
"That really surprised us," Mason said.
"Something is happening very, very early in life in these zoo animals, and it's got to be happening before the age of three or four the average age when wild-caught animals arrive in [zoos]."
Mason doesn't know why captive-bred elephants are dying sooner than their wild-caught counterparts.
But if healthy adults are not able to live long enough reproduce, then the captive populations in Europe won't be self-sustaining—a problem that American zoos already face.
To keep zoo elephants alive longer, the authors recommend routine screening for obesity (something that's done in U.S. captive elephant populations), as well as monitoring stress via a chemical known as interleukin-6.
Checking this biological marker, which shows that the body's immune system is battling sickness, would allow zoo officials to intervene before the animal is seriously ill, Mason said.
Robert Wiese, collections director at the San Diego Zoo in California, was not part of this study. He said making a comparison between the lifespan of captive and wild elephants may seem deceptively simple.
"There are just so many confounding issues, especially in small sample sizes [of] zoo animals, that it's hard to really separate and make sure you're comparing apples to apples," he said.
In 2004 Wiese co-authored a paper in the journal Zoo Biology showing the opposite of Mason's findings: that zoo elephants live as long as those in the wild.
He said that within the last decade accredited facilities have made huge improvements in the care of captive elephants by providing better nutrition to combat obesity, as well as environmental enrichment activities that reduce stress.
"Typically anti-zoo critics throw in our face the things that the zoo community has already identified as issues that we need to work on," Wiese said.
SOURCES AND RELATED WEB SITES