Hibernating animals and climate variable

Asem Rahul *

Tharoi - Seasonal Food items as available at Waithou Keithel in November 2019 :: Pix - Shankar Khangembam

Hibernation is a way of evolution by most animals to survive harsh winters. The present climate variability and change is disturbing the physiological activity in hibernating animals.

Hibernation is like sound sleep. Most warm and cold blooded animals have the capacity to hibernate during winter months. The animal choose safe and well hidden place in order to avoid predators. The process of hibernation differs from one species to another species.

Some start migrating towards warmer regions, other produce thick fat layer and fur coat over their body and some just sleep. Mammals like bats, bears and squirrels undergo hibernation. Reptiles like tortoises and snakes undergo sleep state. Birds like swifts and night hawks, gastropods (snails) as well as amphibians like toads and frogs too hibernate.

There are other lists of hibernating animals that include fish, insects, bees, earthworms, turtles, butterflies, moth, wasps and rodents. Domestic animals hibernate as a result of natural instinct, but with more active periods in between. Scientifically, hibernation refers to a season of Heterothermy characterized by low body temperature, slow breathing, heart rate and low metabolic rate.

As animals hibernate, the body temperature starts dropping due to the lack of activity and metabolism. Soon, the heart beat drops, breathing becomes slow and the blood supply gets restricted to the essential parts. Due to the lack of normal activity, the fat burning process becomes slow and steady. The energy from fat is more than enough to keep the animal alive for the rest of the winter.

In case of cold blooded animals, the normal body temperatures drop with the drop in surrounding environmental temperatures. This means that their body temperatures will match the environmental temperatures. When the temperatures outside begin to change, and the air becomes warmer, these animals will wake up from their deep sleep.

Before the beginning of winter, the animals eat excessively and store the excess food in the form of fat. As winter arrives, they return to their dens or winter nests, where they spend the rest of winter hibernating.

Presently, climate variability and change act as a stressor in hibernating species. In fact, the change is altering the hibernation periods of animals, disturbing their breeding patterns and even change in their metabolic activities. Moreover, the change is pushing the animals towards human populated areas. The activity and physiology of garden snail (Leikang Tharoi) are very sensitive to local temperature and ecological changes.

Studies revealed the change in rainfall patterns and fluctuation in soil temperature leads to the death of juvenile snails. Besides, most of the garden snails are killed to avoid losses in kitchen garden. Furthermore, other edible snails like Tharoi Ningkhaibi (Angulyagra oxytropis), Labuk Tharoi macha (Bellamya crassa) and Labuk Tharoi achouba (Cipangopaludina lecythis) found in the lakes and paddy field are in extremely bad shape as a result of climate change.

Degradation of lakes results in climate variability and change leading to the rise in temperature, precipitation and humidity. Even the river, streams and canal snail like Lai Tharoi amuba ananba (Thiara tuberculata), Tingkhangpanba Lai Tharoi (Brotia costula) and Pung Tharoi (Pila theobaldi) are polluted by toxic substances from the water, especially from the major rivers flowing in the Imphal valley.

In general, most of the gastropods are sensitive to slight changes in environment, such as stability of the bottom, type of sediments, salinity, food supplies, water depth, temperature, oxygen content, and turbidity. Large omnivore’s diet species like bears (Sawom) are shifting their habit and habitats as a result of rapid variation in climate. Most bears (Asiatic Black bear, Sun bear and Sloth bear) found in Manipur shows physiological inactivity during the winter season of the year.

The result of climate variability and change becomes the Ursinae family more aggressive and pushing towards human populated areas. Sometimes, the species are often killed when they prey on livestock or raid crops, or when they roam too close to the village areas. As knowledge, the smallest bear, Sun bear (Helarctos malayanus) is the most arboreal bear, it makes rough nest of bent branches in trees to sleep in.

Until recently, climate has significant influence on the distribution, structure and ecology of forests. The change in climate is probably the most important determinant of vegetation patterns and assumes that the change would alter the configuration of forest ecosystems. Sun bear is now classified as vulnerable species.

The canine was previously listed as data deficient because not enough was known about the species. Over the last decades, scientist suggests small rodents like Kheiroi (squirrel) emerging from hibernation, leaving them less time to eat and reproduce.

In fact, Squirrel is the first sign that creatures are undergoing genetic alteration due to rising temperatures. Above all, numerous studies revealed that seasonal animals are altering with rising temperatures, with many species expected to seek their comfort zone; others which cannot move are likely to become local extinct.

Hibernation is an adaptation process to climate variable and change. During hibernation, the animal conserves energy in order to survive the long winter period when there is lack of food available.

More importantly, genetic variation is significant for future adaptation. Snails can hibernate at any point of time, whether hot or cold temperatures. The presence of thin mucus protects and prevents the species from drying out. Not all snails hibernate, but when they do, the animals have completely enjoyed hibernating. Whereas, the bears sleep whole winter without any break and wake up fresh and hungry in summers.

Small rodents like squirrel sleeps for about 4 to 5 days at a stretch wakes up, eats the food that it collected in summers, take a wee break and sleep for another 4 to 5 days. Hibernation of wood frogs looks like dead one, mostly seen during late winter or early spring of the year.

Freshwater Thenggu (Turtles) hibernate in water where their body temperatures will stay relatively stable and won’t go below freezing. Since they can’t produce their own body heat, it is a must for turtles that they hibernate when temperatures start dropping. It varies from one turtle species to another, but box turtles generally hibernate for three to four months.

Controversy is there where bees hibernate or not. Khoi (Ground bees and bumble bees) hibernate. Other bees do not hibernate; mostly they stick together and survive on food they’ve collected over summer. In addition, some species of Lin (Snakes) experience hibernation in winter, although that depends on the location and place. Sekpi (Bats) will go into the type of hibernation called Torpor when temperatures get cold and they need to conserve energy.

This usually lasts from a couple of hours to a couple of weeks for bats. During this time, the heartbeat can go from 300-400 beats per minute down to only 10. Another cool thing about bat hibernation is that they can use the heat stored within their bodies to help heat them back up again.

Overall, adapting to climate change entails taking the right measures to reduce the negative effects of climate change by making the appropriate adjustments and changes. The Intergovernmental Panel on Climate Change (2007) defines adaptation as an adjustment in natural or human systems in response to actual or expected climatic stimuli or effects, which moderates harm or exploits beneficial opportunities.