Elephants living in the wild don’t have it easy. They face lions, famine, thirst, disease. So you’d think their counterparts in zoos would live much longer. But that’s not the case, according to a survey by researchers who conclude the health and life span of the beasts drops if they are locked up.

Time cites research showing the median life span of African female elephants born in zoos is 16.9 years. Their counterparts in the wild make it to 56 years. There’s a similar difference in Asian elephants.

The report doesn’t alter the Denver Zoo’s plans to expand its collection of the elephants or efforts to raise money for a 10-acre Asian Tropic exhibit, according to The Denver Post.

Meanwhile Paul Boyle, the senior vice president for conservation and education at the Association of Zoos and Aquariums, calls the research “terribly flawed” and says it reflects an “antizoo agenda,” writes The New York Times.