From Wildlife Extra:
Wild mouse lemurs live six times longer than similar-sized mammals
A new study has found that brown mouse lemurs in the wild can live to be up to at least eight years old, which is twice as long as other mammals of a similar size. They were also found to show signs of aging slower than captive grey mouse lemurs, which often display behavioural and neurological degeneration by the age of four, as well as developing grey hair and cataracts.
“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. 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,” commented biologist Sarah Zohdy, post-doctoral fellow in Emory’s Department of Environmental Sciences and Rollins School of Public Health. Zohdy, who conducted the research while at the University of Helsinki, led the study on the brown mouse lemurs in Madagascar. She notes that it is likely factors such as starvation, predation, disease may decrease the observed rate of degeneration (known as senescence) in the wild, but evidence suggests that captivity can adversely affect mental and physical function.
“Comparing longevity data of captive and wild mouse lemurs may help us understand how the physiological and behavioural demands of different environments affect the aging process in other primates, including humans,” says Zohdy.
The study, which took place in Madagascar’s Ranomafana National Park, analysed a total of 420 dental impressions taken from 189 unique individuals between 2003 and 2010. 270 age estimates were calculated during the course of study, based on the wear rates of the mammals’ teeth.
“We found that wild brown mouse lemurs can live at least eight years. In the population that we studied, 16 per cent lived beyond four years of age,” Zohdy explains. “And we found no physical signs of senescence, such as greying hair or cataracts, in any wild individual.”
Hormone analysis of fecal samples from the mouse lemurs was also undertaken, and results revealed that there was no difference in testosterone levels between males and females. Ordinarily in most vertebrates, males tend to die first, so this is an unusual finding. Zohdy explains, “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.”
Mouse lemurs are endemic to Madagascar and are the world’s smallest primate[s]. Although captive grey mouse lemurs can live beyond the age of 12, it is still not known what causes them to show earlier signs of senescence.
It is also not known why brown mouse lemurs in the wild have a much greater longevity than other animals of the same size. Zohdy suggests that the fact that wild mouse lemurs hibernate for half of the year could possibly boost their life span, but further research is needed to explain the findings.
“Our results do not provide information about wild brown mouse lemurs that can be directly compared to senescence in captive grey mouse lemurs,” she says. “Further research, using identical measures of senescence, will help to reveal whether patterns of physiological senescence occur consistently across the genus and in both captive and wild conditions.”
This video says about itself:
29 October 2014
Emory University biologist Sarah Zohdy studies mouse lemurs, the world’s smallest primates, in Madagascar’s Ranomafana National Park. The video shows a pregnant brown mouse lemur at night. “I saw her leap and catch a moth out of mid-air,” Zohdy says. “She then stopped a moment in the trees to clean off her mouth, hands and face, which is what you see on this video.”