Dr Rakesh Kumar Gupta
Many a times we come across with animals that keep on wandering around us throughout the year but hardly observe during winters. So where these animals hide during such dip temperature conditions? And why?
Well! Some few animals such as non-chordates (e.g. Insects, Molluscs etc.) are unable to maintain their body temperature as per environmental conditions while other like bear Hedgehogs, Ground squirrel etc.finding enough food in winter can be difficult, because their main source of food such as insects or green plants is in short supply. In either of cases these animals solve this problem by hibernating.
Some of people have belief that these animals undergo winter sleep. Despite what they may have heard, species that hibernate don’t “sleep” during the winter.Sleep is a gentle resting state where unconscious functions are still performed. While hibernation on other hand is an extended form of torpor, a state where metabolism is depressed to less than five percent of normal. So the fact is their most of the physiological functions are extremely slowed down or completely halted.
So what happens during hibernation? During hibernation the animal’s body reduced metabolic activity and thereby temperature drops, and seemingly its heartbeat and its breathing slow down so that it does not use much energy. Some hibernators go into such a deep sleep that it is almost impossible to wake them, and they appear to be dead!Let’s understand with example, when dwarf Lemurs hibernate, they reduce their heart rates from over 300 beats per minute to fewer than six. Instead of breathing about every second, they can go up to 10 minutes without taking a breath and their brain activity “becomes undetectable.”
How the animals get energy during hibernation? And from where? Basically before undergoing hibernation these animals get ready for their winter sleep by eating extra food and storing it as body fat which they then use as energy while sleeping. In animals there are two types of fat – regular white fat and brown fat. It is the brown fat that forms patches near the animal’s brain, heart and lungs sends a quick burst of energy to warm these organs and perform basic metabolic functions and also help them when it is time to wake up.
Do birds also hibernate? During cold or wet weather, there is always dearth of insects so the parent swifts find it hard to catch enough airborne insects for feeding their chicksat the nest. The chicks, reducing their metabolism to go without food for 48 hours enough to survive until the front passes.But this is actually a semi-torpor, not hibernation.
However one bird is known to be a true hibernator i.e. North America’s common poorwill that often hibernates among rocks during winters.It can slash its oxygen intake by 90 per cent, while its body temperature plummets to 5°C, barely registering signs of life.
(The Author is Lecturer
Zoology, GGHSS Samba).