What is hibernation? And how is it different from aestivation?

Imagine it is weekend: no office, no work, no school, and no commute. The rain is pouring outside. You get up from bed, brew your coffee, stand beside your room’s window, grab your phone, take a picture of your cup, and post on Instagram with a caption “What a lovely day to hibernate!” and you start to binge-watch of your favorite series on Netflix. Indeed, it’s a beautiful day not to do anything but sleep, eat, watch movies, and sleep again.

Now it’s summertime! The weather is perfectly fine and very inviting for swimming, trekking, and doing outdoor adventures. You’re excited to wear your stunning beach outfit, but the sun’s scorching heat could almost burn your skin and toast you like bread. You are torn between getting tanned or staying at home, and you end up turning on your air coolers and cuddling your pillow all day long.

Why do we behave this way? Why do we choose to hibernate when it’s cold and stay outside when it’s hot?

Why do we love to sleep when it’s raining? In an online blog of The University of Melbourne, humans tend to all fall asleep quickly when it rains because of several factors, including increased negative ion level in the air, which has calming and hypnosis effect. The sound of the rain relaxes the brain, and the decreased oxygen content in the air and high water vapor makes us feel refreshed and increased sleep-related hormone called melatonin.
Restricted human activities also summon us to stay in bed.

On the other hand, how do animals adapt to the changing seasons of the year? Well, science has explanations for that.

Humans hibernate because they feel like doing it. However, for some animals, hibernation is a form of survival. According to Kelly Drew, a neuropharmacologist at the University of Alaska Fairbanks, hibernation is a means of energy conservation. It is a state of dormancy evident to endotherms or warm-blooded animals, especially in winter.

During hibernation, the body temperature, heart rate, breathing rate, and metabolism slowed down so animals can conserve energy and survive the winter. Drew’s research in Artic ground squirrels showed that hibernation is often a seasonal behavior but not restricted to cold weather alone. The temperature is not always a factor; some animal species hibernate because of food shortages. Thomas Ruf, an animal physiology professor at the University of Veterinary Medicine in Vienna, also noted that small mammals hibernate to avoid predators.

Animals do not only hibernate as a response to changing weather, but others also aestivate. Hibernation is known as “winter sleep” commonly observed in some reptiles, fish, amphibians, and rodents like chipmunks. However, aestivation is known as “summer sleep” and occurs in animals living in tropical regions and desserts. It is their form of self-protection from extreme heat, dry weather, and scarcity of water. Some species of reptiles, amphibians, mollusks, arthropods, and earthworms do aestivate to save energy and avoid dehydration.

Although the terms “hibernation” and “aestivation” are sometimes used interchangeably, by definition, one is entirely different from the other. Animals do hibernation for a longer duration, while aestivation is for a short period. When hibernating, animals look for warm places to rest and sleep while others look for moist, cool, and shady places to aestivate. Besides, hibernation is for warm and cold-blooded animals like mammals and birds, while aestivation is for cold-blooded animals only including snails and frogs. The only commonality between them is that they are ways of animal adaptation to different weather conditions by suppressing their metabolic processes and saving energy, whether winter or summer.

With adverse weather conditions caused by climate change and global warming, only those who can adapt to changes are most likely to survive. Humans develop technologies, construct resilient buildings and houses, convert lands to settlements, and exploit the forests for our consumption. As we progress and advance, let us also remember that we are not the only animal occupying the Earth. Because if we overexploit and abuse our nature, time will come that no matter how hard other animals hibernate and aestivate, they can no longer survive the mess humans created. Let us live in harmony with other members of the Animal Kingdom.

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