‘Sleep No More’ Awakens After a Long Hibernation

Animals that hibernate appear to have the proper concept for those who dislike winter: It’s the same as hiding under the bedclothes until spring, right? Just barely. Learn more about the science of hibernation by reading on.

For those who are Unfamiliar, Please Explain Hibernation.

Hibernating animals don’t “sleep” through the winter despite popular belief. Hibernation is essentially a prolonged type of torpor, a state characterised by a decrease in metabolism to less than 5% of its normal level.

Marina Blanco, a postdoctoral associate at the Duke Lemur Center in Durham, North Carolina, United States, studies the dwarf lemurs (Cheirogaleus spp. ), the only primates that hibernate on a regular schedule, and she says that during hibernation “most of the physiological functions are extremely slowed down or completely halted.”

‘Sleep No More’ Awakens After a Long Hibernation

While hibernating, the heart rate of a dwarf lemur drops from around 300 beats per minute to about six, according to Blanco. And instead of taking a breath every second or so, they can continue for up to ten minutes without oxygen. Their mental state “becomes imperceptible.”

Contrast this with sleep, a condition of quiet rest during which conscious awareness is suppressed but unconscious processes continue. Blanco’s studies have shown that hibernators require occasional arousals to ensure enough rest.

The Question is: Why do Animals Nibernate?

Kelly Drew, a neuropharmacologist at the University of Alaska Fairbanks in the United States, puts it plainly: “Hibernation is a strategy of energy conservation.” She does research on Arctic ground squirrels’ brain chemistry as they hibernate (Spermophilus parryii).

Hibernation is frequently associated with the winter months, however it is not exclusive to cold-blooded creatures. Some tropical species hibernate during the hot summer months.

There are situations where temperature plays no role. The lack of food causes hibernation in other species, Drew says. In Australia, echidnas, for instance, will go into hibernation after a fire has occurred, emerging only when food supplies have recovered.

An further, protective, motive has been proposed in recent research. Hibernating makes an animal “extremely hard to detect for predator,” according to Thomas Ruf, a professor of animal physiology at the University of Veterinary Medicine in Vienna, Austria. He found that tiny mammals have a monthly mortality rate five times higher when awake than when hibernating.

Is There Anything That Actually Occurs During a Hibernation?

Animals typically lower their core body temperature by 5 to 10 degrees Celsius (9 to 18 degrees Fahrenheit) in order to reduce their metabolism. Drew’s research subjects, Arctic ground squirrels, can supercool much more, to temperatures below freezing.

According to Drew’s findings, adenosine levels in the brain are responsible for controlling body temperature. Ground squirrels’ adenosine receptors become more responsive as adenosine levels rise throughout the winter.

However, animals rarely remain in this frozen stupor for the entire dormant season. Intermittently waking up and warming up consumes about 80% of their energy.

Ruf calls the motivation behind this “one of the greatest mysteries” of the field. Some believe they must restart their immune systems in order to fend off sickness, while others believe they may simply be reawakening in order to get some rest.

Scientists have discovered that animals remain active for longer amounts of time during arousal periods as ambient temperatures rise, using up more of the energy they are trying to conserve during hibernation.

Which Species of Animals Hibernate?

In addition to the one known bird, several amphibians, reptiles, and insects show signs of hibernation-like behaviour. The metabolism of at least one fish, the Antarctic cod (Dissostichus mawsoni), drops by a factor of 20 during the colder months of the year.

Plus, there are a great many different kinds of animals. Even though bears are perhaps the first to come to mind, debate has raged over whether or not they are actual hibernators for years. When in hibernation, bears can sleep for up to a hundred days without waking to eat or defecate, and they can be woken from their slumber far more quickly than other hibernating animals. They may be super hibernators, according to the National Park Service of the United States.

Mammals that hibernate tend to be little in size. Hibernators, on average, are very light, with Ruf stating that their typical weight is only 70 grammes. Because it is more difficult for smaller animals to maintain body heat during the colder months due to their bigger surface area to volume ratios, they benefit more from seasonal energy savings.

How Long do Hibernating Animals Typically Sleep?

An award for longest hibernating period is more difficult to determine than you may imagine. The wild edible dormice (Glis glis) that Ruf studies are a natural fit for this description because they may hibernate for over 11 months.

Their body weight needs to be doubled or perhaps tripled when they are physically engaged for this to be possible. Their name comes from the Romans, who found the meat of these hibernating mammals to be a tasty treat, hence the term “delicacy.”

A big brown bat (Eptesicus fuscus) hibernated in a refrigerator for 344 days (though it didn’t chose to do so and didn’t survive), suggesting bats may deserve the moniker.