What's your secret to staying warm in the shivering winter-time in Hong Kong with climate changing? - maybe a jumper over t shirt...? When body heat loses faster than it is generated or absorbed, animals, including humans, may risk to have hypothermia’s scythe put on the neck. As local research suggests, each degree Celsius dropped below 24°C potentially brings 3% increase in death toll. Other than hibernation and fur coat, animals in the wild have more wintry adaptations beyond our expectations.
Regulating body temperature by thermoregulation, i.e. to boost production and absorption of heat by behavioural adjustment thus reduce heat loss from body surface, safeguards body temperature from falling below dangerous levels. Check out the five ways of how wild animals keep themselves sane in the penetrating chill.
Adaptation No.1 - Basking
Sunbathing is the most cost-effective way for temperature boost. Cormorant spreads its feather out to embrace the most sunlight with the largest body area. The Madagascar-exclusive Ring-tailed lemur (Lemur catta), interestingly, faces its belly to the sun, like a meditating yogi. Sunlight to cold-blooded animals is a particularly indispensable heat source due to their environment-sensitive body temperatures. Next time when you are in winter excursion, try to pay more attention to the open areas - you are very likely to be amazed by the sunning lizards!
Adaptation No.2 - Hiding
However, the limited daytime in winter makes sunlight an unreliable heat source. Instead of exposing to the outdoor threat, some animals would simply burrow themselves into the ground to shun the chill. Just like human love wrapping ourselves like a real-life burrito, frogs prefer to dig deep into the soil for a hot sand bath.
Adaptation No.3 - Curling
Body volume to surface area ratio determines the speed of heat loss. If the surface contacts with cold air raises, space for heat conversion increases, resulting in a faster body heat loss. Therefore, animals like hedgehog curls its body up into a ball in order to retain heat by lessening its cold-air contact surface. Guess what? Among all 3D objects, a sphere has the least volume to surface area ratio - how terrific the wisdom hedgehog has!
Adaptation No.4 - Rubbing
Hands rubbing has become an anti-cold reflex of human. Otter, spending most of its time underwater to prey, has a similar cold-resisting flair. When leaving the water, otter rubs its face for warmth and a nice hair comb, which also creates a thin insulation layer trapping the heat in its fur.
Adaptation No.5 - Huddling
Many is mighty. Gregarious animals huddle one another for the common warmth. As blizzard blows in, hundreds to thousands Emperor penguins (Aptenodytes forsteri) in the Antarctica quickly flock together. They form packed and tight concentric circles, sticking with each other to stand the ferocious snowstorm. What’s more, penguins in the inner circle will orderly move outward, switching roles with their defender buddies in the outer circle.
Similarly, overwintering danaids in Hong Kong flutter together to stay themselves warm. Bunches of danaids gather and hang on the trees for warmth. They will part once the temperature rises.