If primates and mammals can hibernate, surely so can humans. At least that’s what many scientists believe. With the secrets of hibernation slowly being revealed, ‘human hibernation' might not be too far-fetched or outside the realm of possibility
Millions of years ago, perhaps with the first ice age and the ground and rivers frozen solid with several feet of ice, any creature that wanted to survive had to either move to warmer areas or begin to adapt. Evolution decided it needed to keep up or move out. Of course evolution of life itself had begun with the first multi-celled organism and it was life’s ability to replicate itself that propelled species into the future. Of course it took longer than a blink of an eye, but then again in earth time what is a few thousand yearsIJ To survive the ice age some animals flew, some walked, others grew hair and fur and some decided to simply go to sleep and wait for the weather to get better. Hibernation is a strange and complex process that has fascinated scientists who have been trying to decode it. My first brush with a hibernating individual was in my parents room during the winter when I accidentally found a snoozing ‘chhipkali’ behind some books. It suddenly sprang to life and scuttled away. Not all animals can snap out of hibernation that easily though. Bears are usually the first animal most people would think of when it comes to hibernation and for good reason.
Bears hibernate for about six to eight months in a year. lynn Rogers, an American biologist has spent a lifetime studying black bears and is famous for his study technique. He has formed trusting relationships with wild black bears and has spent 24-hour periods with them eating, sleeping and walking. On one study trip he accidentally fell into a den and onto a hibernating bear! luckily the bear was in a deep state of hibernation and didn’t wake up for eight minutes even though her cub bawled loudly. Rogers got lucky, what we now know is that bears are not ‘true hibernators’ they do in fact wake up quite often in the middle of their hibernation and some individuals might even be light sleepers. Pregnant bears will wake up to give birth, clean the cubs and then go back to sleep and the cubs will stay next to her, suckling and awake for the remaining months of slumber. A hibernating bear will reduce its heart rate down to about 25 per cent and bring down its breathing and metabolic rate to a much reduced level. Depending on what period of the hibernation it is, a bear could take anywhere from several minutes to almost none to wake up. Recently, researchers who had tagged and attached monitors to a bear observed that even when they approached the den and made minimal sound, the heart rate of the hibernating bear would start to increase. It seems that bears like people can behave and react quite differently to the same stimulus and have individual personalities which reflect this.
While it hibernates the bear’s fat cells break down to provide water and calories and the organs and muscles break down to provide protein. Sounds like they’re doing more harm than goodIJ Evolution found a way around it. The urea in their urine that is produced when the tissue breaks down has nitrogen in it, bears use the nitrogen to build new proteins that go directly to the organ and muscle tissue and keep them healthy. In spite of all these amazing abilities bears are still not considered ‘true’ hibernators by some scientists. According to them a ‘true’ hibernator will actually drop its body temperature down to match the environment and often it is below freezing!
What is most impressive about true hibernation and what intrigues biologists is that the state of hibernation brings the body’s functions down to the bare minimum that is needed to stay alive. Salty body fluids have a lower freezing point and keep the body tissue from crystallising and the metabolic rate drops to just two per cent above dead. This is an extremely complex physiological change where literally a warm-blooded animal transforms itself into a cold-blooded one for a prolonged period of several months. Only three orders of mammals display this unique behaviour — the Erinaceomorpha, Chiroptera and the Rodentia, in simpler words hedgehogs, bats and rodents including marmots, hamsters and ground squirrels.
The Arctic ground squirrel burrows beneath the surface and builds itself an insulated nest of grass and hair and curls up into a ball to hibernate. With toes and tail tucked in, the squirrel begins to drop its body temperature lower till it is near the ambient temperature, and remember this is the Arctic. It’s breathing down to just about three irregular breaths a minute it appears quite dead and is practically in a self- induced coma.
So deep is this hibernative state that it doesn’t react to any disturbances and even physical handling. All bodily functions almost come to a complete standstill and all the resources of the squirrel’s body are used to maintain and keep this fine balance where a level any lower would certainly lead to death. As deep as this true hibernation is, the Arctic squirrel takes a break and wakes up about every three weeks, moves around a bit and goes right back to sleep.
Interestingly, it is not just the animals freezing their tails off that hibernate, animals in hot desert climates also hibernate but it’s known as estivation. The triggers are the same but at the other extreme. High temperatures and lack of food and water sends them underground where it’s cooler. In Australia, the water-holding frog has evolved a technique where it buries itself in sandy ground and forms a water-tight cocoon made of mucus around itself. Aborigines discovered this way back and in times of drought have used the frog to their advantage. Once a frog was found it was squeezed and made to empty its bladder. Half a glass of diluted urine might not be the preferred choice of drink but in a harsh environment survival is the only instinct. Some other animals that estivate are earthworms, snails, turtles, bees, lizards including the common ‘chhipkali’.
While estivation is not very common in mammals, in 2004, Kathrin Dausmann, an animal physiologist discovered a species of lemur that estivates for upto seven months. Soon after two other lemurs in Madagascar were discovered that could estivate. They keep their bodies cold and take a breath only once every several minutes. So if primates can hibernate, mammals can hibernate, why can’t humansIJ Well that’s what the scientists are asking and today with the secrets of hibernation slowly being revealed ‘human hibernation’ might not be too far-fetched or even too far away.
(The writer is a wildlife filmmaker)