Of course, humans don’t actually hibernate: Our heart rates, breathing and metabolisms can’t automatically come to a crawl and our temperatures can’t drop causing us to go into long bouts of torpor to allow us to conserve energy. However, hibernation expert Hannah Carey at the University of Wisconsin-Madison says that inducing us into some form of decreased metabolic state might not be out of the realm of possibility someday.

A hibernating 13-lined Arctic ground squirrel. Photo courtesy of Hannah Carey.

“If we knew everything about how they did it, it’s possible that we could use that information to manipulate human metabolism or mimic other aspects of hibernation,” says Carey. “We could induce humans and other animals into a mild dormant state, which could, for example, limit damage of vital organs until accident victims can get medical aide.”

This and many other things we have recently discovered about several extreme nappers are squashing many old assumptions about hibernation being only a cold-climate defense tactic.

It’s not just for animals in cold climes or even nonprimates anymore

Here are some other surprising facts about 10 expert sleepers, some of which live in the tropics or deserts:

1. Dwarf lemurs and mouse lemurs in Madagascar are the only tropical primates known to hibernate. They can do so for months to accommodate periods in which resources become scarce. The fat-tailed dwarf lemur hibernates seven months out of the year in tree holes in Madagascar, where winter can be as warm as 86 degrees F. Its body temperature can fluctuate as much as 36 degrees daily to accommodate fluctuations in temperatures in its hole.

2. Black, brown and grizzly bears are the largest hibernators. Given their size, it actually takes a lot for them to power down and back up again, so while their heart rate drops from, say for black bears, an average of 55 beats at rest in the summer to as few as nine per minute during hibernation, their body temperature is only lowered a few degrees and ranges from 86 to 97 degrees F. Living off of five inches of stored fat for five to seven months while hibernating, they won’t eat, drink or urinate, in spite of waking up periodically and then again returning to hibernation.

Click here to view the embedded video.

Check out these live bear cams and videos of black bears denning, some with cubs, at the North American Bear Center in Minnesota.

3. Bats drop their heart rates from hundreds of beats per minute to a low of about 25 beats per minute during hibernation. However, given their relatively small size, if bats are woken during winter when their insect meals cannot be found, they could easily use up their fat stores and starve.

4. Many North American rodents, from desert-dwelling kangaroo rats and rock squirrels to tiny forest-dwelling dormice, will go dormant for hours to days and then wake up to snack on stored foods to get by in cold months. (Watch these captivating videos of dormice from ARKive.)

5. But marmots, ground squirrels and jumping mice hibernate for weeks just off of accumulated body fat. In fact, the Arctic ground squirrel can hibernate for up to 250 days this way by lowering its body temperature down to nearly 27 degrees F—the lowest of animal known mammal.

6. The nightjar or common poorwill is quite uncommon actually, as it is the only bird known to be able to slow its metabolic rate and drop its body temperature for days or weeks when its food, night-flying insects, are not available. It lives in dry, open grassy or shrubby areas in western North America. 

7. In winter, some amphibians and reptiles go into a state of brumation in which they are awake and although they will drink water, will not eat. North America’s only poisonous lizard, the gila monster, lives in deserts in parts of the southwestern United States and Mexico. This mostly nocturnal predator feasts on small mammals, birds, other lizards, frogs and eggs, and then lives months without food by storing fat in its tail and becoming dormant in its burrow.

8. Some reptiles will aestivate, or lower their own body temperature to protect themself against extreme heat, like the desert tortoise of the North American Southwest. It will aestivate in summer and then hibernate most of winter, from about October to March.

9. The pupfish lives in the deserts of southwestern North America. At the end of summer when shallow springs, ponds, marshes, and slow-flowing streams dry up, most pupfish will die, having lived less than a year. In some areas, by late summer, surviving pupfish will start to become dormant in burrows at the bottoms of remaining waters.

10. Many insects will pause at different stages in their development, or diapause, in winter but also when food or water might be limited in summer, like desert locusts.

Why Hibernate?

Some researchers have noted that during the last 500 years, those species that spend some periods of time in torpor with lower heart rates are also less likely to go extinct, perhaps because they are able to adjust better to drastic changes in food availability or temperatures. This could be valuable information, as so many species are being affected by climate change.

Who knows what else we might learn from these expert sleepers? Perhaps that state of suspended animation we see in science fiction movies isn’t entirely out of reach. As Carey puts it, “We are very loyal to that 98.6 degrees Fahrenheit,” so I know I’ll be envying our hibernating brethren during the next winter months as I reach for my next cup of coffee.

A group of young Colorado chipmunk siblings takes an outing in this photo by George Aldridge, an entrant in NWF's annual photo contest.

We’re not here to talk about those chipmunks, though. We’re here to take a look at 10 things you probably don’t know about chipmunks that neither sing nor star in films. Real chipmunks. Ten things.

1. Chipmunks are basically tiny squirrels (1 to 5 ounces) that have adapted to burrowing. Other members of the squirrel family (Sciuridae) include woodchucks, prairie dogs, various ground squirrels and, of course, tree squirrels.
2. North America is home to 21 chipmunk species, according to the Smithsonian Institution.
3. Chipmunks produce one or two litters a year. Young are on their own within eight weeks.
4. Chipmunks prefer forested areas and can climb trees, shrubs and…birdfeeders.
5. They eat various types of seeds as well as fungus, helping to spread the mycorrhizal fungi that live around tree roots and are critical to tree survival. Chipmunks also spread the seeds of trees and other plants.
6. Chipmunks aren’t particularly choosey about what they eat. Along with seeds and fungi they scarf grain, fruit, nuts, insects, worms, bird eggs and even nestling birds and baby mice. They probably don’t hunt for eggs and hatchlings, just eat them when they find them.
7. They might not sing like Alvin and the boys, but wild chipmunks do vocalize. Kenneth Schmidt, a biologist at Texas Tech University who studies eastern chipmunks, recognizes three chipmunk calls, “the chip, the deeper chuck, and the startle call.” The last is an alarm that warns of impending danger. Chipmunks will even make calls in a chorus composed of several of the little rodents—shades of Alvin. Simon and Theodore. Hear how chipmunks sound.
8. 

   An eastern chipmunk in Masschusetts, photographed by Vladimir Mikhaylov, an NWF photo contest entrant, has packed its mouth with leaves for use in lining its nest.

   Ground-nesting veeries and ovenbirds, Schmidt recently discovered, avoid setting up house in areas where they hear chipmunk squeaks, thus reducing the risk that the squirrels will eat the birds’ eggs and young. Chipmunks also listen in on the alarm calls of other species, says Lisa Aschemeier, a biologist at Ohio’s Northwest State Community College. She has found that chipmunks respond to the high-pitched alarm whistles of their relative the woodchuck, sometimes seeking cover after a woodchuck warning. Woodchucks, she says, pay less attention to chipmunk alarms, presumably because, at up to 12 pounds, they are so much bigger and need not fear as many predators as chipmunks do.
9. In autumn, chipmunks gather seeds and other foods for storage as a supply of winter food. Some species keep food in their burrows, which can be more than 10 feet in length.
10. Alvin and the Chipmunks are now 53 years old. Wild chipmunks, on average, live two to three years; captive specimens have lasted eight.

Bonus Item: Chipmunk Hibernation

Chipmunks hibernate in winter, but they don’t sleep all the way through the season. They retreat to their burrows but wake every few days, raise their body temperatures to normal, feed on stored food rather than fat reserves, and urinate and defecate.

When chipmunks are in the deep sleep phase of hibernation, they may be very difficult to arouse. Their heart rate declines from about 350 beats per minute to perhaps 4. Body temperature may drop from 94 degrees F to whatever the temperature of the burrow—as cold as 40 degrees F.

A new study has found that as winter temperature heats up because of global warming, chipmunks in warmed areas become less likely to hibernate in the coldest months. The research indicates that chipmunks that follow normal hibernation procedures enjoy a survival rate through winter of about 87 percent, while those that remain active because of warm winter weather are almost certain to die by spring. The scientist who made this discovery, Craig Frank of Fordham University, fears that this evidence could suggest dire
results for other hibernating species as climate warms.

NOTE: All photos accompanying this blog were donated by entrants of the annual National Wildlife Federation Photo Contest. You can see the 2011 winners in Photo Zone.

A woodchuck, or groundhog, during the warm months of grassy abundance.

The groundhog, also known as the woodchuck or the mouse bear (because it looks like a miniature bear when sitting upright), first won its reputation as a weather prognosticator in 1886, when the editor of western Pennsylvania’s Punxsutawney Spirit newspaper, one Clymer Freas, published a report that local groundhogs had not seen their shadows that day, signaling an early spring.

This story begat Punxsutawney Phil, the legendary woodchuck weathercreature, which begat Ground Hog Day and the familiar idea that Phil (and his namesake successors down through the years) can predict the perpetuation of winter.

It is likely that the story of Phil is based on European beliefs that badgers and hedgehogs can provide signals about the future; lacking those species in his area, old Clymer substituted the local animal that most resembles a badger or a hedgehog.

But the groundhog is much more than a weather rodent. It’s also a real animal with a real life.

Here are 10 things you may not know about this roly-poly rodent:

1. Groundhogs are among the few animals that are true hibernators, fattening up in the warm seasons and snoozing for most of three months during the chill times.
2. While hibernating, a woodchuck’s body temperature can drop from about 99 degrees to as low as 37 (Humans go into mild hypothermia when their body temperature drops a mere 3 degrees, lose consciousness at 82 degrees and face death below 70 degrees).
3. The  heart rate of a hibernating woodchuck slows from about 80 beats per minute to 5.
4. Breathing slows from around 16 breaths per minute to as few as 2.
5. During hibernation—150 days without eating—a woodchuck will lose no more than a fourth of its body weight thanks to all the energy saved by the lower metabolism.
6. During warm seasons, a groundhog may pack in more than a pound of vegetation at one sitting, which is much like a 150-pound man scarfing down a 15-pound steak.
7. To accommodate its bodacious appetite, woodchucks grow upper and lower incisors that can withstand wear and tear because they grow about a sixteenth of an inch each week.
8. If properly aligned, woodchuck upper and lower incisors grind away at each other with every bite, keeping suitably short; when not in good order, they may miss one another and just keep growing until they look like the tusks on a wild boar; if too long, a woodchuck’s upper incisors can impale the lower jaw, with fatal results.
9. Woodchuck burrows, which the animals dig as much as 6 feet deep, can meander underground for 20 feet or more, usually with two entrances but in some cases with nearly a dozen.
10. Burrows provide groundhogs with their chief means of evading enemies, because the rotund little guys (just before hibernation, a hefty woodchuck may tip the scales at 14 pounds) are too slow to escape most predators in a dead heat: the rodents have a top speed of only 8 mph, while a hungry fox may hit 25 mph.

Bonus Fact: Although groundhogs may not be the best weather predictors, they do in fact emerge from dens in early February. This is the practice of males as they rouse themselves to wander around their 2- to 3-acre territories in search of burrows belonging to females, which the males will enter and where they may spend the night. Research suggests that no mating takes place at this time; the visits probably just let the animals get to know one another so that they can get right down to the business of breeding when they emerge for good in March. Outside of the mating season, woodchucks are solitary, except for females with young, which usually are born in early April.

Before we skip to the furry hibernating good stuff, a bit of background on this annual celebration. A recent Kaiser Family Foundation study unearthed the fact that American children spend 7 hours and 38 minutes per day using electronic media. It’s no wonder it seems our kids recognize more corporate logos than species of wildlife. NWF hopes children will take a walk on the wild side this week—and stay there, for their physical health and engagement with the natural world.

Spring Has Sprung!

The vernal equinox sprung clocks ahead this weekend, so we benefit from one more hour of daylight to get out and explore. Around this time, much of the animal kingdom is waking up from their winter hibernation. Animals like bears, chipmunks, and groundhogs are leaving their dens and stretching their legs for the first time in months.

Black bears are one of the masters of hibernation—they can go for more than three months without eating, drinking, or even going to the bathroom. Black bears do not get dehydrated, because their body reabsorbs and utilizes waste so the bear can keep on resting. What’s even more fascinating is that during this whole process, female black bears are pregnant.

During the deepest part of hibernation, the development of the unborn cubs is delayed. In late winter, the pregnancy resumes and black bear females wake up and give birth within their den. With her new cubs, the mother slips into a half rest as she continues hibernating and feeding the growing baby bears. The whole family emerges from the den in the beginning of spring, and mama bear is in desperate need of a meal!

While bears go on a marathon fast during their hibernation, chipmunks depend on late-night snacks. Chipmunks cannot store fat and energy the way bears can, so they need nearby food to munch on so they can maintain a healthy temperature. Chipmunks will sleep for a few days, wake up eat, and then go back to a hibernating state.

Did you know Belding’s Ground Squirrels can hibernate for more than seven months? Visit www.nwf.org/WildlifeWeek to learn more, and check back tomorrow for Tuesday Tweets!

Check out this video to see NWF’s David Mizejewski talking about wildlife and weather for March 2010!

Additional References: PBS and eNature.com

Photo Credit: Warren Cooke, porcupine – Douglas Island, Alaska