Mouse Lemurs Reveal the Secrets of Aging

Even while living amongst predators, and battling disease, starvation and environmental stressors, wild mouse lemurs manage to survive, and new research helps reveal their secrets of aging.

Researchers were surprised to find that these mouse-sized primates can live at least eight years in the wild - twice as long as some previous estimates. That's compared to just four years in captivity, they add.

The secret to their lack of senescence lies in their sex and testosterone levels, according to the study, described in the journal PLOS ONE.

Led by biologist Sarah Zohdy, researchers decided to focus on wild mouse lemurs in Madagascar's Ranomafana National Park.

"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," Zohdy explained in a statement.

Using a unique dental mold method to determine their ages, researchers found that living longer was something that occurred in both males and females, unlike most vertebrates where males tend to die first. Mouse lemurs, found only on the island of Madagascar, are a female dominant species, which may explain why both genders have the same testosterone levels.

While elevated male testosterone levels have been implicated in shorter lifespans in several species, this is one of the first studies to show equivalent testosterone levels accompanying equivalent lifespans," Zohdy said.

Mouse lemurs may be the world's smallest primates (weighing a mere 30 to 80 grams), but they typically can live six times longer than mammals of similar body size, such as mice or shrews. Captive gray mouse lemurs (Microcebus murinus), for example, can live beyond age 12.

So how does this study suggest that those living in the wild may actually fare better than their captive counterparts? Well, according to the results, by age four captive conditions may start to affect lemurs' mental and physical function. In addition to slowing of motor skills and activity levels, reduced memory capacity and sense of smell, they can start developing gray hair and cataracts.

"We found that wild brown mouse lemurs can live at least eight years," Zohdy added. "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."