After the festive period, many of us have gorged on food and feel suitably stuffed to the point where we could sleep for a few months. Many animals are in hibernation over the winter months, but what do their bodies do during this time, why do they hibernate in the first place, and why don’t we?
Hibernation is a period of time when an animal goes into extended inactivity, taking shelter from predators and the colder weather. During this period, an animal’s metabolism slows down dramatically to a quarter of its usual rate, cooling the animal’s body down and reducing its heart rate to only a few beats per minute! What triggers such changes and how do animals know that it’s time to do this?
As the weather changes and the days shorten, animals begin to increase their body fat in preparation for the months ahead. During winter months, food is in short supply and it takes more energy to maintain a constant body temperature. It is commonly assumed that hibernation is a type of sleep but in fact it may not be a form of sleep, just a really efficient way to conserve energy (e.g. long-term torpor). This explains why naturally hibernating animals which are kept in a zoo tend not to hibernate in captivity; when resources are plentiful, and surroundings comfortable, the animals do not need to undergo hibernation. Scientists have been in search of ‘hibernating genes’ to explain why some animals hibernate and others do not, but are yet to have any success. In fact, very little is known about the biological science behind this process itself, other than its triggers.
How do the hibernating animals know when to wake up again? Signals such as warmer surroundings and lighter days are a good indicator for the animals to know that they should start to come out of their slumber. Winter is not the only time of the year when animals are known to hibernate. Some reptiles go into a type of hibernation called aestivation, which they practice in the hottest months to avoid periods of drought and extreme heat, finding cooler underground holes in which to rest.
It’s all well and good for the lucky animals that hibernate through the colder weather, but what about us? Why don’t we hibernate through the winter? During these months we find ourselves slowing down, watching more TV, eating much more, and curling up on the sofa for numerous early nights. Researchers hope to answer the genetic questions of hibernation and harness its ability to be used in space travel. A journey to Mars would take at least 6 months travel but further exploration into the solar system, or other galaxies, could take years. Ideally, astronauts would be able to conserve their energy and sleep through vast periods of such space flight, reducing the amount of supplies needed to be taken to sustain life. The most achieved to date are impressive meditation techniques practised by Buddhist monks where they have been recorded to reduce their heart rate by 64%. Researchers are currently investigating if a human hibernation state can be reached by lowering body temperature by ~5oC, reducing metabolic rate by 50-70%. A technique such as this is already used in hospitals when people have undergone large trauma, keeping the bodies at a reduced temperature for a few days whilst the body begins recovering. It is hoped that this can be applied to space travel and for longer periods of time.
Whilst many of us feel drowsy during the shorter, colder days and seem to stockpile on food and drink during the winter months, human hibernation is still a way off and will impact space travel before it reaches everyday life. Animals take advantage of their biological ability to harness hibernation, conserving energy and avoiding harsh conditions. Hopefully, scientists will be able to identify genes or a biological switch which is the key to this evolutionary trait which hibernating animals possess, and thus enable us to further our exploration into the great beyond…