After Jonas – one of their captive dwarf lemurs – died at nearly 30 years old, researchers from Duke University Lemur Center in Durham, NC, decided to look for clues that might explain his long lifespan.
Image credit: David Haring, Duke Lemur Center
They reveal what they found – after combing 50 years of the Center’s medical records – in the Journal of Zoology.
The records covered medical data on hundreds of dwarf lemurs and three other lemur species. Jonas was one of a particularly long-lived clan of fat-tailed dwarf lemurs.
It appears that one of the reasons behind the dwarf lemurs’ surprising longevity is their ability to put their bodies into a state of suspended animation known as torpor.
The data showed that the amount of time the animals spend in this standby state is linked to how fast they age and how long they live.
As a general rule in nature, the larger the species, the longer it lives. Whales and humans live to 100, lab mice rarely reach their fourth birthday.
Dwarf lemurs are one of the exceptions – this hamster-sized species can live two to three times longer than other species of a similar size.
We also know that hibernating lemurs live 10 years or so longer than their nonhibernating cousins.
The researchers found that dwarf lemurs can spend up to half the year in deep hibernation in the wild. In captivity, they usually go into semihibernation for up to 3 months.
But the researchers suggest even the shorter time spent in hibernation in captivity appears to lengthen the animals’ lifespan.
They found that hibernating lemurs not only live longer, they also stay healthier and are able to have offspring long after their nonhibernating relatives have passed that stage.
The researchers found that while nonhibernating lemurs can reproduce for 6 years after they reach maturity, hibernating lemurs continue to have offspring for 14 years after maturity.
Also, while all the species they found data on suffered from the usual age-related diseases such as cataracts as they aged, the hibernating ones seemed to experience symptoms much later.
When they hibernate, the hibernating lemurs put their bodies on standby and slow everything down. They drop their heart rate from 200 to 8 beats per minute and they slow their breathing.
They also switch off their thermostat – so instead of using up metabolic energy to maintain a constant internal temperature, their body allows it to go up and down in line with their surroundings.
For most primates, such a behavior would be life-threatening. But it seems to work for lemurs – they conserve energy during the times when food and water are scarce.
Some scientists have suggested the reason hibernators stay healthier and live longer is because they spend more time snoozing underground, where they are less likely to be found by predators.
“But the fact that we see the same pattern in captivity, where they’re protected from predators, suggests that other factors are at work,” notes co-author Sarah Zehr, a researcher at the Duke Lemur Center.
Another reason, suggest the researchers, could be that being in a state where everything slows down may also slow the oxidative damage in cells that is a natural side-effect of breathing and metabolism.
The researchers hope their findings will help with the search for anti-aging genes in humans, especially as lemurs are more closely related to us than mice, which are frequently used as research subjects.
Funds for the study came from the German Research Foundation, the US National Science Foundation, the Rufford Foundation, the MMBF/Conservation International Primate Action Fund, Primate Conservation, Inc. and the Margot Marsh Biodiversity Foundation.
In April 2014, Medical News Today reported how – since her death in 2005 – scientists have found over 400 genetic mutations in the healthy blood cells of a 115-year-old woman who left her body to science. They said their findings offer clues about the limits of human longevity.