David Haring, Duke Lemur Center
Jonas, the world's oldest known dwarf lemur, died this January just months shy of his 30th birthday. Duke researchers are using lemurs like him to study the biology of aging.
March 13 has been deemed World Sleep Day by the World Association of Sleep Medicine, which hopes to call attention to problems that arise from sleep disorders. Presumably, the sleep researchers were thinking about humans when they declared the day, but it made us think of animals, too. After all, many critters don't need any reminders about the importance of sleep. They're already so on top of the job that some animals sleep
of the day (and we're looking at you on that, koalas!). Let's tip-toe past some of nature's big sleepers as they snooze away or get ready for a nap. We start right in the average pet owner's home, with cats and their sometime chums, dogs. We're told to let sleeping dogs lie, and this one's feline friend seems to be heeding the advice.Dogs Strut Their Stuff at Westminster 2015: Photos
Koalas are super-sleepers, racking up about 20 hours per day toiling away at their slumber. If sleep were a superpower, koalas would have their own Hollywood superhero tentpole franchise built on the premise that they fight crime, but only between naps.Crazy About Koalas? We Are, Too: Photos
Sloths in captivity have been known to sleep some 15 hours per day, but in the wild they don't clock as much shut-eye. Fairly or not, though, they're right up there with koalas in being associated with sleep.VIDEO: Sloths Are A Walking Ecosystem!
In the jungle, the mighty jungle, the lion sleeps tonight. Okay, not quite -- lions are largely nocturnal and do most of their sleeping during the day, as we can see here. The king of the jungle sleeps a bit more than half its day, for around 13 hours.Lounging Lion Pride Wins Wildlife Photo of the Year
Tigers are as sleepy as lions, often a bit more so, lounging for about 16 hours each day. This Bengal cub seems to have gotten the hang of it.White Bengal Tiger Cubs Make Their Debut: Photos
This yawning bat is ready for some hanging-upside-down time.Bizarre Sighting: Cane Toad Eating a Bat?
How is a lemur supposed to get any sleep with all this racket? This one tries the shield-your-eyes trick.Madagascar's New Animal Haven: Photos
Horses are known to take a load off, perhaps even bedding down for a snooze amid some daisies.
A sleepy red panda dreams of bamboo shoots.Giant Panda Comeback Also Helps Neighbors: Photos
When fat-tailed dwarf lemurs hit the hibernate button, they increase their overall longevity.
So suggests a new study by Duke University researchers, who reviewed more than half-a-century's worth of medical records on hundreds of dwarf lemurs and three other lemur species that either do not hibernate or do so only opportunistically.
The researchers found that the longer the animals spent in hibernation the longer they tended to live, and the slower typical aging symptoms presented themselves.
In fact, the team found, the hibernating lemurs lived as much as 10 years longer than other lemur species that did not hibernate.
When a dwarf lemur hibernates, it can take its heartbeat from some 200 beats per minute down to a barely-there 8 beats per minute. Its breathing slows and its internal body temperature rises and falls with that of the air outside instead of remaining steady.
Lemurs do this for classic hibernator reasons: to conserve energy and make it through periods when resources are scarce.
Just how long lemurs hibernate can vary between those in captivity and those in the wild, the scientists said. Earlier this year, the oldest known fat-tailed lemur -- a 29-year-old named Jonas -- died. In the wild, the Duke team said, animals like Jonas form an extreme end of the spectrum, spending up to half of the year in hibernation.
Meanwhile, the researchers said, lemurs in captivity hibernate for at most three months. "But even that seems to confer added longevity," said study co-author Sarah Zehr, a researcher at the Duke Lemur Center.
The hibernators also held typical aging symptoms at bay longer than their always-on cousin lemurs. The researchers observed that while every species they studied developed cataracts and other age-related eye diseases as they got older, hibernating lemurs did not develop such problems until much later in life.
One rationale used by some researchers to explain lemur longevity is that simply hibernating and avoiding predators for X amount of time will, of course, prolong their lives.
"But the fact that we see the same pattern in captivity, where they're protected from predators, suggests that other factors are at work," Zehr said.
The animals' hibernation might also protect cells against the normal buildup of damage that comes with metabolism and breathing, study co-author Marina Blanco noted.
"If your body is not 'working full time,' metabolically-speaking, you will age more slowly and live longer," Blanco said.
The researchers hope their work with lemurs could one day aid in the hunt for genes in humans that forestall aging. Their findings appear in the March issue of the Journal of Zoology.