World's Smallest Primate, the Mouse Lemur, Lives Twice as Long in the Wild (VIDEO)

Tiny, mouse-sized primates called mouse lemurs can be found on Madagascar. Now, scientists have discovered that the world's smallest primate lives twice as long as previous estimates, calling into question current practices when keeping these animals in captivity.

"It's surprising that these tiny, mouse-sized primates, living in a jungle full of predators that probably consider them a bite-sized snack, can live so long," said Sarah Zohdy, one of the researchers, in a news release. "And we found individuals up to eight years of age in the wild with no physical symptoms of senescence like some captive mouse lemurs start getting by the age of four."

So why do wild lemurs fare better than captive ones? It's likely that starvation, predation, disease and other environmental stressors reduce the observed rate of senescence in the wild. It could also be that captive conditions affect mental and physical function.

"We focused on wild mouse lemurs because we want to know what happens naturally when a primitive primate is exposed to all of the extrinsic and intrinsic mortality factors that shaped them as a species," said Zohdy. "Comparing longevity data of captive and wild mouse lemurs may help us understand how the physiological and behavioral demands of different environments affect the aging process in other primates, including humans."

The researchers found no difference in longevity between male and female mouse lemurs. They also found no difference in testosterone levels between the genders. Because higher testosterone levels have been implicated in shorter lifespans, this particular phenomenon could explain the equal lifespans.

"We found that wild brown mouse lemurs can live at least eight years," said Zohdy. "In the population that we studied, 16 percent lived beyond four years of age. And we found no physical signs of senescence, such as graying hair or cataracts, in any wild individual. We now know that mouse lemurs can live a relatively long time in the wild, but we don't know the exact mechanisms behind why they live so long."

The findings are published in the journal PLOS One.

Want to see a mouse lemur for yourself? Check out the video below, courtesy of YouTube.