In the Northern Hemisphere, it’s prime hibernating time.

It’s cold, it gets dark early, and, to be honest, eating a ton and just kinda-sleeping until the end of winter sounds really great right about now. But I can’t do that, at least, not naturally.

I’m not a bear, or a bat, or any of the other animals you might be picturing, snug in their dens until the sun comes back. I’m just a primate, desperately in need of a vacation to somewhere tropical, somewhere warm, somewhere that I wouldn’t have to hibernate to make it through the winter. Except, the thing is, there’s another primate that got to this island paradise first.

And it hibernates in the tropics. And, oh yeah, it also might hold the key to long distance space travel. [ ♪ Intro ] There is only one group of primates in the world that is known to hibernate, with one possible exception, and that group doesn’t include us, unfortunately. Meet the dwarf lemurs.

There are nine species of these adorable little guys and they’re only found on Madagascar, like all lemurs. And this month, our Bizarre Beast is the chipmunk-sized fat-tailed dwarf lemur. They live in dry deciduous forests, mostly on the western part of the country.

And when I picture a tropical island, I think it’s going to be hot, humid, and sunny, pretty much all the time. But that is just not how Madagascar works. Because, here’s the thing about this island.

It has a lot of different kinds of ecosystems, ranging from cloud forests to the so-called spiny desert, and it’s home to something like 5% of the planet’s biodiversity. More than 80% of the species that live there are endemic, they’re found nowhere else on Earth. This includes everything from most of the plants of the spiny forest, to all of the lemurs, to all of the amphibians!

And part of what creates the different habitats that these critters are adapted to is the island’s seasonality. On the west coast, where our lemur lives, the difference between seasons isn’t just about temperature, it’s also about rainfall. From April to October, winter in the Southern Hemisphere, there basically isn’t any rainfall at all, and there aren’t other water sources for the lemurs, either.

Winter here basically means that it’s the dry season, though it does also get much colder at night than it does in the wet season. And, because the environment the fat-tailed dwarf lemur lives in has such extreme differences between seasons and, thus, available resources, they’ve adapted to hibernate to make it through the lean times. Now, hibernation isn’t just a deep sleep.

It’s the often-seasonal, multi-day version of a condition called torpor, where an animal’s body temperature, metabolism, and other physiological processes are reduced in order to conserve energy. Some animals actually do this on a daily or nightly basis, including many marsupials and hummingbirds. And even critters that truly hibernate don’t stay in a state of torpor for the entire hibernation season.

They alternate between periods of torpor and interbout arousal, where they warm back up for a bit. In the fat-tailed dwarf lemurs, those warm-up periods happen every six to twelve days during their up to seven months of hibernation. And they make it through by living up to their name.

They stuff themselves on sugary fruits and nectar when they’re abundant and store those precious calories as fat in their tails. They can put on up to 40% of their total body weight in tail fat! The other species of dwarf lemurs also store fat in their tails, but the rainforests where they live have less extreme seasons, so they put on relatively less fat and have shorter hibernation periods.

So, okay, if these tiny primate relatives of ours can hibernate, what’s stopping us? We know that the fat-tailed dwarf lemurs have to hibernate to make it through the dry season in the wild. But in places like the Duke Lemur Center, if they stay warm and have food year-round, they don’t hibernate, though they do go into brief periods of torpor, so there’s clearly some kind of on-off switch.

For the fat-tailed dwarf lemurs, it looks like a combination of low temperature, long nights, and less food triggers hibernation. And inducing torpor in people by lowering their body temperature is something that’s done in certain medical procedures, but not for long enough for it to count as hibernation, so there has to be more to it than that for us. Because hibernation would really be the goal for making things like long distance space travel possible, and it’s something that NASA has been funding research on since 2014.

One hurdle that we’d have to get over is our brains. Part of what happens in the lemurs during the interbout arousal periods when they warm up is REM sleep. Which is actually kind of a funny thought, that animals seem to need sleep to recover from hibernation.

But some researchers have suggested that torpor is actually more like being sleep-deprived than like being asleep, at least from your brain’s perspective. We aren’t sure why this is the case, but we’d need to figure out how to protect our brains from the effects of long-term torpor before we try to send anyone to Mars. Another hurdle is that we don’t have the same kind of ability to store fat and use it in yearly cycles as the dwarf lemurs.

We also don’t have a convenient tail for storage! A dwarf lemur hibernation expert we spoke to for this episode, Dr. Marina Blanco, speculated that storing fat in the tail might make it easier for these tree-living primates to move around or that it might be a safer place for the lemurs to store fat, from a health perspective.

We know that, in people, having a lot of fat around your organs can be associated with medical problems, it might be a similar situation for lemurs. If we could figure out this part of the hibernation equation for space travel, we also might be a step closer to using that knowledge to treat metabolic conditions like diabetes. So it seems like the fat-tailed dwarf lemur still has a lot of primate hibernation secrets to share.

And maybe my dream of hibernating for the winter isn’t as far away as I thought. We want to give a special thanks to Dr. Marina Blanco, Dr.

Lydia Greene, and the Duke Lemur Center for their help with this episode and for the use of all this incredible footage and images and all these little fuzzy guys! The pin club subscription window is open now through the end of December 5th, and it makes a great gift! The lemur pin is just so cute.

Sign up today and you’ll get the lemur pin in the middle of the month and the pins after that around the time each new video goes live. And make sure you like and subscribe to our channel so you never miss a beast! As always, profits from the pin club go to support our community’s efforts to decrease maternal mortality in Sierra Leone. [ ♪ Outro ]