If you live in the norther part of the norther hemisphere, you should have noticed: it’s getting colder outside (No way, are you serious?!). As most of life’s processes require heat in some form, the outside temperature will significantly interfere with our abilities to do so. More energy is needed to overcome the lack of heat and this energy could be scarce. This could have psychological effects for some people like insomnia or oversleeping or listlessness. However, we can protect ourselves relatively easy from the cold by putting on some extra warm clothes, staying inside our houses or offices more often. In addition we are capable of generating artificial heat and we can easily buy and store our food close-by and use it as needed.
But how do other creatures protect themselves from cold? Some avoid the cold weather altogether and ‘hibernate’ in a warm country (of course, some people also use this strategy). This does require a long trip and therefore lots of energy. The upside is that the animals that migrate, remain active. Those that stay in a colder climate, use various strategies. The most obvious one that comes to mind is a thick layer of fat and fur. This does require some preparation before the winter starts. More food needs to be found and consumed as it will cost energy to grow the fur/fat and to carry it around.
Another way is to shut down almost completely. This can be seen two ways. During the last part of summer and all the way through fall, certain trees and plants will store their nutrients that are normally present in the leaves, in their roots. A consequence of this is a colouration and eventually a loss of the leaves, because they serve no purpose anymore. Plants that do this are called deciduous. The so-called evergreen plants and trees do not lose their leaves, because they often have small, strong leaves (needles) and perhaps waxy substances in them which enables them to protect themselves against colder circumstances.
Hibernation or a long winter sleep is also an example of near metabolic shutdown. Certain animals will find a hiding place where they can sleep for several months. Their metabolism is brought down to a low level, which also leads to lower physiological activities in the brain, heart, stomach etc. As energy is still needed for basic survival (breathing, low heart rate), some animals will combine this strategy with the first. A winter sleep doesn’t mean that the animal is sleeping all the time. From time to time, the animal will wake up, but it isn’t very active. Some insect species also hibernate, but instead of having a thick fur or layer of fat, they often have black bodies (for heat absorption) or produce high levels of glycerol that acts almost like antifreeze to protect their tissues. In a way, humans use these two strategies too. The wintercollection of clothes has dark colors and to prevent or treat a dry skin, bodylotions are used which contain glycerol.
Some creatures live less than a year. To prevent losing their precious lives because of cold and a lack of energy, these creatures avoid the cold by spending the winter period in their egg or larvae phase. During summer the adults mate and lay the resulting eggs in shielded places (in trees, underground, in your house!), which remain dormant untill the outside temperature increases again around springtime, causing the eggs to hatch. The adults die in the fall/winter season, and are ‘ replaced’ by the new generation in the spring. Examples of creatures using this strategy are some mosquito species, praying mantids and plants such as corn, peas and beans.
There are some scientific studies on inducing hibernation in humans. Not just for fun, though! Scientists think that the ability to induce hibernation in humans will help when someone is suffering from a critical illness or was victim of an accident. For more info see this link. Some scientists take the potential application of human hibernation a bit further by investigating whether this could be used for long space journeys (for example to get from Earth to Mars with as little energy as possible). One can also speculate that it would benefit the economy if humans would actually hibernate (fewer accidents due to slippery circumstances, less seasonal depressions, lower waste of energy, higher efficiency in working during spring/summer).
As always, your thoughts are appreciated!