arctic fox by emma j bishop cc

There’s nothing quite as contagious as a yawn* (Photo: Emma J. Bishop, Creative Commons license)


Grab forty winks. Saw logs. For a species that’s habitually short on shut-eye, we humans sure have come up with myriad ways to talk about it. We also spend a lot of time and money studying sleep, or the lack thereof. Yet, in spite of decades of inquiry, researchers still don’t have a good fix on why we—and just about every other living creature—need to nod off.  We’ve had better luck trying to understand other unconscious states, especially those employed by certain non-human species to deal with hard times.

yawning prairie dog by SearchNetMedia ccWinter poses a critical challenge for animals who stay put rather than migrate to warmer climes. Thermoregulation requires calories, but many foods—especially fruits, nectars, vegetation, and insects—are scarce when the days are short. The ability to reduce one’s energy needs can be a life-saving adaptation. Hibernation does just that—it lowers an animal’s metabolic rate. If all goes well, this period of inactivity, which may last several days, weeks, or even months, depending on the species, will stretch stored energy reserves (aka body fat) long enough for the animal to survive until a greener season. “If” depends on many factors, such as the abundance of autumn food resources, the length and severity of cold days, and even the stability of the den site during repeated freeze-thaw-freeze cycles.

When a critter—let’s use the chipmunk (Tamias spp.) as an example—transitions into a state of hibernation, its body temperature drops to near freezing, breathing becomes so shallow as to be imperceptible, and the heart rate decreases dramatically, from 350 to 4 beats per minute.  Although we tend to think of hibernation as a season-long slumber, chippies and other hibernating rodents do wake up every few weeks to have a snack and take a potty break, even though these periods of activity, called interbout arousals, consume up to 90% of stored body fat. There are some champion nappers in this chisel-toothed group—including the groundhog (aka woodchuck, Marmota monax), who sleeps half its life away, setting the alarm for March when it heads to bed in September.

Other examples of sound sleepers include: insectivores like the European hedgehog (Erinaceus europaeus) and the tenrecs (Microgale spp.); the mountain pygmy possum (Burramys parvus)—the only hibernating marsupial; and the echidna (Tachyglossus spp.), a monotreme.  Biologist recently added the mouse lemur (Microcebus spp.) and the fat-tailed dwarf lemur (Cheirogaleus medius) to the hibernator roster; prior to this discovery, we didn’t have any examples from among the primates. Additionally, since winter temperatures in their native Madagascar may reach 86° F (30° C), it’s become clear that hibernation isn’t strictly associated with cold weather. Nor is it limited to mammals; a bird called the common poorwill (Phalaenoptilus nuttallii) snoozes through at least some of the snowy season.

yawning polar bear by Paul Davidy ccIronically, that most famous of North American sleep icons, the bear (Ursus spp.), is the subject of much debate. The question is whether or not they are “true hibernators.” Bears often spend far more time sleeping than the so-called “trues,” so what’s all the fuss about?  Well, this is going to sound like nit-picking, but here goes. First of all, a bear’s heart rate drops, but not quickly enough to suit some scientists. Also, while the number of heartbeats may go as low as 8 per minute, the average is closer to 50 per minute. Moreover, during this time the bear’s body temperature remains pretty close to normal. This is a handy little idiosyncrasy that, should the need arise, allows the animal to wake up fast… and often cranky—a fact Santa (and anyone else) should keep in mind when planning a mid-winter visit to the den.

Taking to one’s bed for months on end could be seen as a rather over-the-top response to a simple cold front. It smacks of swooning characters in English romance novels from the late 1700s. Frankly, it’s not everyone’s cup of tea, and many wild critters take a more measured approach. Torpor is the term commonly used to describe these shorter, less dramatic forms of dormancy, although, technically, hibernation and other types of suspended animation are really subsets of torpidity. Call it what you will, there are examples of “temporary hibernation” in all the Classes of vertebrate animals—mammals, birds, reptiles, amphibians, and fish—and it’s commonplace among the myriad spineless critters.

For some of the busiest bodies, torpor is a daily habit. Hummingbirds (Trochilidae), for example, have such a high metabolic rate that they need to ingest a steady stream of non-carbonated sugar water (i.e., nectar) during their waking hours or they’ll become hypoglycemic and are too exhausted to fly. Can’t fly? Can’t feed. It’s a vicious circle that will ultimately lead to the bird’s death without some kind of intervention. As you might imagine, this need to constantly refuel creates an enormous problem when night falls and these feathered perpetual motion machines must rest. Without some way to temporarily lower their metabolic rate, hummingbirds would never be able to get out of bed in the morning. Never fear—torpidity to the rescue!

rock dove yawning by Tatiana Bulyonkova ccSwifts (Apodidae), chickadees (Paridae), nightjars (Caprimulgidae), and doves (Columbidae) are just a few of the other avian species who go torpid under various conditions. Generally speaking, these birds are fruit-, nectar-, or insect-eaters, and they tend to be on the small side (less than 80g). The snowy owl (Bubo scandiacus), at 1600-2950g is one exception to this rule, and biologists recently added a second, when it was confirmed that the tawny frogmouth (Podargus strigoides) goes torpid during Australian winters.  Personally, I find these new insights into animal behavior thrilling, because they reassure me that what we know about wild creatures is still a drop in the bucket compared to what we don’t know—there are worlds upon worlds waiting to be discovered on this blue gem of a planet we call home.

yawning turtle by Michael Ransburg ccOf course, cold is not the only hardship wild things would rather sleep through. Periods of drought are just as serious a threat to survival, especially for aquatic and semi-aquatic species. When a lake, pond, or stream goes dry, the inhabitants need to dig in. Literally. Turtles and tortoises (Testudines), crocodiles (Crocodylidae), frogs and toads (Anura), salamanders (Caudata), and some crustaceans will aestivate (also spelled estivate)—a drought-driven form of hibernation. They sink down into the mud before it dries completely, sealing themselves in a mucous capsule until the rains come again. If ever there was a time to be glad you can absorb oxygen in the soil through your skin, this is it, because the air in your boggy bubble won’t last very long.

yawning snowy owl by Pat Gaines ccResearchers are intrigued by these alternate forms of sleep and how they might offer clues for solving a variety of human health concerns. Honestly, I understand their fascination but I don’t know how they stay awake long enough to collect any data. Just writing about dormancy has my eyelid feeling so… heavy. I guess it’s… time for…. me to turn… in.

…..Hit the  YAWN!  hay.

……….Catch some…..zzzzzzzzz


*Pop Quiz:  How many times did you yawn while reading this? 😉



There’s nothing quite as invigorating as finding a little Next-Door Nature in your email inbox—click the “subscribe”  link in the upper right-hand corner of this page and receive notifications of new posts!
© 2011 Next-Door Nature—no reprints without written permission from the author. Thanks to these photographers for making their work available through a Creative Commons license: SearchNetMedia (prairie dog); Pau Davidy (polar bear); Tatiana Bulyonkova (rock dove); Michael Ransburg (turtle); and Pat Gaines (snowy owl).

You haul

eastern chipmunk

Eastern chipmunks carry nuts and seeds in cheek pouches to underground food caches for use in winter (Photo: Gilles Gonthier, Creative Commons license)


Moving supplies have been dominating my thoughts of late and taking over my apartment too. With boxes stacked everywhere the walls are, quite literally, closing in. When claustrophobic thoughts threatened this afternoon, I took a deep breath and remembered that wide, open spaces were waiting outside.

But a funny thing happened when I walked through my front door into a bigger world. I promptly fell into a smaller one.

I was sitting beneath a favorite shade tree, just letting my mind wander anywhere it wanted to go that didn’t involve packing, when my adventure began. Staring absently at the clover 6’ beyond my feet and growing sleepy, I wasn’t even startled when a pointy, soil-dusted nose suddenly pushed it’s way, dreamlike, to the surface. In short order the nose became an Eastern chipmunk (Tamias striatus), complete with rusty-brown face, two bright, black eyes, curious, mobile ears, small hands, and a slender torso. Of course, vertical stripes are always slimming.

Maybe I was large and still enough to be perceived as part of the tree. Perhaps a long to-do list was urging her on to the tune of “I’m late, I’m late, for a very important date!” Either way, that rodent paid no attention to me at all as she immediately set to work. I settled in to watch, sure I’d found the perfect distraction from my own busy schedule… but then she started packing.

No, she didn’t pull cardboard boxes and rolls of tape out of that hole in the ground. No need, when you’ve got a steamer trunk in each cheek. Okay, technically they’re pouches, but they are used to transport things from one place to another. Lots of things—this species has fewer molars than other chippies so there’s extra room. What do chipmunks need to carry? Some plant-based bedding now and then, but mostly groceries. During the summer their diet includes perishables such as wild fruits, bird eggs, insects, and other small creatures. These items are consumed immediately. Nuts and seeds are naturally long lasting, so they end up in underground caches. When you need both your arms and legs to get around, there aren’t any limbs left for lugging things to and fro. Ergo… you stuff your face.

chipmunk on a bird feederWhen the cheeks are full, they may double the size of the chipmunk’s head. Think Dizzy Gillespie. Believe it or not, there are people who spend time documenting and reporting what chipmunks pack into these pouches, and we’re not talking small potatoes. Seriously—the pouches are big, but they’re not that big; an adult chipmunk is smaller than your average restaurant Idaho. The cheeks are large enough, however, to hold 70 black-oil sunflower seeds, 31 dried corn kernels, or 13 prune pits (where do chipmunks find prune pits I wonder… curiouser and curiouser).

As the small face in front of me grew wider, I began to doubt that it would fit back through a 2” opening without leaving behind some of the payload. I forgot that by this time of year, even a young’un would be an old hand at this. She dove into the entrance without a second’s hesitation… and me right on her heels, having conveniently shrunk down to chipmunk size (in my mind, that is—there weren’t any bottles labeled “Drink Me” at hand).

I’m not Alice and this was no rabbit hole, so we didn’t fall into a chasm. The whole burrow was only 18-36″ below the surface. She scampered along an 8’ tunnel towards a labyrinth of chambers and passageways, darting past what appeared to be a nesting area into the pantry; one of many pantries, actually, although technically, I think these rooms are referred to as hoards. From November through March or April, chippie chick and her kin will spend most of their time underground. If the weather above is warm enough, they’ll venture out to forage, especially if there’s a handy bird feeder nearby, but chipmunks rely primarily on foods put up during the summer months. Not a true hibernator, they arouse now and then from periods of torpor. When they do they need to eat, and there’s no cake in this Wonderland.

Or books, or dishes, or clothing, or any of the other myriad items waiting to be stuffed into the cartons I’m using instead of pouches. But my belongings won’t pack themselves and my new friend is busy taking care of her own business. “Time to leave Wonderland,” I thought, shifting ever so subtly. And with that, I was instantly transported back to my favorite tree, watching a tail tip disappear into a hole in the ground. Definitely time to return to the land of boxes and rental trucks… and cake!

When I head out for more supplies I think I’ll stop at the grocery store for a treat. This is one cake that doesn’t need to say “Eat Me.”  With all the bending and lifting and stair climbing I’ve done today, I can have a slice without fear of growing too large to fit in my apartment.


© 2011 Next-Door Nature— no reprints without written permission from the author. Thanks to Doug Cadmus for making his photo of a chipmunk feasting at a bird feeder available through a Creative Commons license.

Bearly spring

black bear

American black bears sleep through much of the winter, setting their alarm clocks for April (Photo: Pat Gaines, Creative Commons license)


Obviously, she hasn’t looked at the calendar recently or Mother Nature would know the vernal equinox has come and gone, and there should not be tiny snowflakes drifting past my window on this grizzled April morning. It’s enough to make a gal want to hibernate a while longer. Crawling back into my quilted den, thoughts turned to ursine sleepyheads cautiously probing the air with a fur-covered nose, vacillating, as I am, between warmth and a grumbling stomach.

The abdominal alarm clocks of American black bears (Ursus americanus) are beginning to clang. Further north and west, the bears settled in to snooze 6-7 months ago. Because fall foods such as acorns, hickory nuts and beechnuts, and other high-calorie treats are usually more abundant on my side of the continent, East Coast bears don’t tend to head for bed until November or December. The night owls of the family, they may be light sleepers as well; Virginia winters are comparatively mild, so during warm spells bears may rouse and emerge to forage.

There used to be some debate over whether or not bears actually hibernate, although that particular argument seems to have been put to rest. When ground squirrels and other small mammals hibernate, their body temperature drops to near freezing. When hibernation was defined solely in terms of temperature reduction, bears did not qualify as “true hibernators.” Once researchers discovered it’s a depressed metabolism that drives the temperature loss, and that bears do undergo significant metabolic changes that allow them to den for over 7 months without eating, drinking, or producing liquid and solid waste, our understanding—and definition—of hibernation changed; it now includes bears.

Dr. Michael Vaughan, a professor in the Department of Fish and Wildlife Conservation at Virginia Tech and Director of the Virginia Bear Research Center in Blacksburg, dreamed of learning even more about hibernation and how it might offer clues to improving human health. When people are sedentary due to an injury, illness, or even space travel, it can lead to osteoporosis. Bears, on the other hand, experience some bone loss during their long periods of inactivity, but they also continue to create bone. By examining the hormones that play a key role in bone formation and breakdown, Dr. Vaughan and his team are trying to unlock the bears’ secret to keeping bone cell production on autopilot during bed rest.

How can bears nap for so long without heading to the refrigerator (which, in the case of a bear, would be the great frozen outdoors beyond their den) with a case of the midnight munchies? By following the Boy Scout motto: Be Prepared! Many Homo sapiens have to work hard to keep from gaining weight, but it’s a different story for Ursus. They can’t just saunter up to the counter at McDonalds® and start super-sizing. Even for urban bears, who have access to restaurant dumpsters, it can be a challenge to pack on enough fat stores to survive the deep sleep. A male black bear needs to gain as much as 30 pounds per week, so autumn preparation consists of attempting to consume 10,000 to 12,000 calories—the equivalent of 18-21 Big Macs®—per day.

Compared to that, motivating myself to throw back the covers with the promise of French toast for breakfast sounds downright… slimming.

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© 2011 Next-Door Nature— no reprints without written permission from the author.