When temperatures plummet and the seasonal blues kick in, a familiar thought often blows through our minds with the winter winds: “I wish I could just hibernate through all of this!” It certainly has an allure. Why can’t we just choose to tap out and rest for weeks on end? And from a sales perspective, that idea is undoubtedly enticing to those of us at Sleep Outfitters. With Groundhog Day here at last, we put our best team of researcher on the job (yours truly) to get to the bottom of hibernation and why it eludes us human-folk. And it turns out we simply do not need it.
But before we discover why we can’t, we must first understand why some do. It shouldn’t surprise you to learn that it’s more than just “a long nap.” Hibernation is a state of suspended animation, an incredible adaptation that enables animals to conserve energy by remaining inactive for days, weeks, or even months at a time (and in the peculiar case of edible dormice, even up to 11 months). Endothermic, warm-blooded animals generate body heat internally and need a constant source of energy to keep moving, provided to them by food. When extremes in weather leads to food scarcity, animals are forced to adjust to survive or die. Some migrate to warmer lands periodically, while some hibernate to better utilize the reserved energy in their fat. Generally speaking, smaller creatures are less likely to migrate and more likely to hibernate, and the opposite is true for larger animals, considering the amount of energy required to warm up their bodies.
Several things can signal to an animal it’s time to hibernate: length of day/night, temperature change, food supplies, internal clocks, and so on. Traditionally, these are linked to seasonal changes, with winter regularly associated with the practice; in fact, the word itself derives from Latin hibernare, which means “to pass the winter.” (However, a “hot hibernation” known as aestivation occurs among animals in deserts and tropical climates, burrowing to avoid the punishing heat.) During hibernation, metabolism and breathing slow as body temperature and heart rate drop dramatically, all to conserve energy. Variances occur in how often certain species wake to relieve themselves, snack or drink, with some never stirring throughout. Though fish, birds, amphibians, and reptiles often lie dormant during colder months, hibernation is more generally associated with mammals (see below). Examples of some hibernating mammals include rodents, bats, bears (kind of…see below), and even some primates such as lemurs in Madagascar.
(A distinction is often made between hibernation and torpor, a sleep-like state interrupted by frequent bouts of wakefulness. This can occur as often as a daily basis. Many more creatures participate in this phenomenon, which for our purposes we’ll just refer to as a light hibernation. Bears, for instance, are much too large to enter a traditional hibernation and instead experience torpor during winter months, where they don’t eat, drink or relieve themselves for about six months, though do awaken periodically and are responsive. They even give birth during torpor!.
In nature, of course, survival consists of more than just food supply. You also have to avoid becoming someone else’s food supply, another factor contributing to hibernation’s evolutionary lasting power. "Until recently people thought hibernation was just about energy saving, a defense against cold weather and food shortage, and now we think it's more predator avoidance," said Thomas Ruf of the University of Veterinary Medicine in Vienna, Austria to BBC Earth. "We know that the survival rates in hibernation are close to 100%." Hibernators tend to decrease annual reproduction rates and increase their own longevity, as well. Hibernation can function as a battery saver function, extending an animal’s life beyond what nature might intend.
Given all this, it might now be more apparent why humans do not partake in the ancient practice, but there are some specifics that color in the details. Humans have evolved from tropical ancestors in equatorial Africa, only later migrating to more temperate and sub-arctic climates. Our hearts can’t operate below 28°C, while hibernating animals can beat at 1°C. Though we might’ve developed a biological imperative for hibernation over time, humankind in all its wisdom found what we deemed to be superior alternatives: fire, clothing, shelter, hunting, and agriculture. Why shut your body down when you’ve got a fur coat, a fish, and a fire?
“Well, for sleep!” you might be sleepily interjecting at your computer screen. Bad news on that front: it may be the case that hibernation isn’t even restful. Given the massive physiological changes taking place, many animals must follow hibernating with periods of sleep to catch up. And if you’re like me, that’s reason enough to stop envying the groundhog. Experiments have been made, however, to induce a hibernation-like state that’s been successful in mice that if eventually applied to people could potentially help stabilize accident victims, slow a disease’s progress, or more effectively aid radiation therapy for cancer patients. Hibernating for a good cause. For now, though, I’ll stick with my nightly rest, courtesy of a properly fitted mattress from Sleep Outfitters.