Tag Archives: hibernate

A young fat-tailed dwarf lemur living at the Duke Lemur Center shows the characteristic calorie-packed tail the animal uses to fuel up to 7 months of hibernation. CREDIT : David Haring, Duke Lemur Center

Study of lemur hibernation reveals secrets that might one day help humans hibernate as well

The fat-tailed dwarf lemur, native to the marvelous isolated ecosystem of Madagascar, is the closest human relative known to hibernate. After studying the sleeping behavior of both captive and wild lemur specimens, scientists at Duke University have discovered a great deal about how hibernation works in lemurs. The key discovery is that they can go for days without the  deepest part of sleep, along with other insights related to body temperature and metabolism. Hopefully coupled with further knowledge to be gained in the future, scientists might one day devise a method that will also allow humans to hibernate – the only for humans to survive a trip from Earth to neighboring solar systems using conventional propulsion methods.

A young fat-tailed dwarf lemur living at the Duke Lemur Center shows the characteristic calorie-packed tail the animal uses to fuel up to 7 months of hibernation. CREDIT : David Haring, Duke Lemur Center

A young fat-tailed dwarf lemur living at the Duke Lemur Center shows the characteristic calorie-packed tail the animal uses to fuel up to 7 months of hibernation. CREDIT : David Haring, Duke Lemur Center

Why do we sleep? You might find this funny, but the key function of sleep is still rather poorly understood. What’s certain is that it’s important, otherwise our bodies, as well as those of most complex organisms, wouldn’t dedicate a third of their lifespan to it. We know sleep is important for regulating body temperature. For instance, during the body’s peak surface temperature, sleep is warranted and this is when we actually get sleepy, seduced by melatonin which starts bathing the brain. At the end of the sleep cycle, the body is the coldest. Also, studies have shown that it is during sleep that most of the information we gather during waking life is processed and memories are consolidated. Finally, sleep plays a role in regulating the metabolism. How, what are the mechanisms and whether indeed these occur due to sleep in the first place are questions that have so far been answered in mixed opinions.

The theory that sleep is vital to temperature and metabolism regulation is supported by the recent study by Duke scientists of the Madagascar lemurs –  a squirrel-sized primate. These tiny primates live up to seven months each year in a physiological state known as torpor (a form of hibernation), where the regulation of body temperature stops and metabolism slows down. Amazingly, the lemurs can  drop their heart rate from 120 beats per minute to a mere 6, and breath extremely crawled. You haven’t heard the best part yet. We humans, like most mammals, have organisms deeply dependent on body temperature. It’s enough for a variation of 2 degrees Celsius to kill most of us, yet the lemurs’  bodies heat up and cool down with the temperature of the outside air, fluctuating by as much as 25 degrees in a single day!

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That may be extreme for humans, but for lemurs the skill is paramount to survival during the long  winter dry season (not that cold for most of us – 10°C and even lower during the night), a time of year when food and water are in short supply.

The researchers then wanted to know what happens when the lemurs sleep, so they attached electrodes to the animals’ scalps and returned them to their nests for monitoring. The researchers also measured oxygen intake and other vital signs. Duke scientists measured periods of brain activity consistent with the phase of sleep known as rapid eye movement (REM) sleep — when most dreaming is believed to occur — but only when winter temperatures rose above 25 degrees Celsius. Interestingly, the lemurs went for days without the slow-wave when in torpor – the  low-amplitude brain activity associated with deep sleep.  People who use poliphasic sleep (sleeping in cycles of say 1 hour every 4 hours) also typically get lees deep sleep, while still feeling rested (not a sleep pattern for the faint of heart, though!).

Next, the researchers plan on studying other hibernating mammals – a family of small hedgehog-like animals called tenrecs. Hibernating would not only help humans actually travel through interstellar space, but also pose practical solutions in present day. Being able to push humans into standby mode by temporarily reducing heart rate and brain activity could buy time for patients who have suffered head trauma or heart attacks, extend the shelf life of transplant organs.

Krystal AD, Schopler B, Kobbe S, Williams C, Rakatondrainibe H, et al. (2013) The Relationship of Sleep with Temperature and Metabolic Rate in a Hibernating Primate. PLoS ONE 8(9): e69914. doi:10.1371/journal.pone.0069914

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Researchers look at hibertnating bears for the first time

Bears are some of the most amazing and loved animals out there, and to find out that up until a few months ago nobody made a thorough study about their hibernating was really sad for me. Until this, almost everything we knew about hibernating was that… well, bears do it’; they go into their dens and come out a few months after that looking a whole lot skinnier, and of course, hungrier.

But researchers from the University of Alaska at Fairbanks and Stanford University weren’t satisfied with just that, so they set on a quest to find out the details of this long winter sleep that bears do; in order to understand it, they studied five bears that had been caught by local authorities wandering too close to civiliziation. It was really important and hard to find such specimens, because when in captivity, their natural cycles get all mixed up, so studying them shows little scientific information, and as for wild ones… you never should wake a sleeping bear – even if you work at Stanford.

These five bears were kept in specially designed dens that had infrared cameras, and they “showed” researchers that during hibernation, the bears’ metabolic level drops to 25%, even though their body temperature goes down way less. During the theoretical 5 months of hibernating, they do not eat, drink or defecate – all they need is air. What good could this do for humans ?

‘If you could reduce the metabolic demand of people, it’ll be favourable either during surgery or as a quick response during heart attack or stroke or trauma,’ Barnes said. ‘What that would do is give you more time. We like to say it would potentially expand the ‘golden hour’ – during which, if you reach advanced medical care, outcomes are better – to a golden day or a golden week.’

It does show great promise indeed, but researchers have yet to figure out how do bears lower their metabolism to such drastic rates. Another more interesting, but even more speculative use for this research would be long distance space travel, because with our current means and what we have in sight, even traveling to Mars will take a really long time.