Which animal lives in a freezing temperature

Animals in winter

Survive in the freezing cold

Various adaptations allow animals to survive the cold season. Some species make do with their own antifreeze, others are masters at reducing heat radiation.

In the freezing cold, surrounded by snow, a yellow butterfly can be seen hanging from a small branch. The lemon butterfly is not frozen to death, although some snow crystals are showing on its body. The tender animal is the only native butterfly that manages to overwinter in the adult stage. To do this, it doesn't even have to seek shelter protected from the weather, as various other insects do. How could it carry its large wings undamaged into a hollow plant stem or into a hole in the ground?
In contrast to larger animals, insects cool down very quickly when the ambient temperature drops. So it would be inconceivable that the butterfly could maintain a high enough body temperature not to freeze. His body cells are protected from frost damage because they contain a kind of antifreeze. Cell constituents such as glycerine are concentrated to such an extent by water excretion, among other things, that the freezing point of the body fluid drops to around minus 20 degrees C.
The strategy of protecting themselves from freezing with antifreeze is shared by the robust brimstone butterflies with numerous other insects and other animals that have to survive in the extreme cold. Antarctic fish have special antifreeze proteins in their blood that prevent them from freezing. These proteins bind to small ice crystals and thus prevent their growth. Otherwise the ice crystals would be very dangerous for the animals, because they cause irreparable damage when they pierce the membranes of the individual body cells.


Extreme cold tolerance

There is at least one animal that survives freezing: the Panagrolaimus davidi worm. This Antarctic nematode lives under truly extreme conditions between mosses and algae on an Antarctic coast that is temporarily free of ice and snow over the course of the year. Liquid water and life-friendly temperatures are only available from time to time in its habitat. The worm can survive the complete drying out of its body as well as the complete freezing in order to come back to life in better circumstances. It seems that various protective mechanisms are used.
A few animal species such as some frogs and turtles can tolerate the freezing of body fluids outside of their body cells, whereby the cell membranes remain largely protected. In this way, the North American forest frog, a particularly cold-tolerant relative of the native common frog, survives the Nordic winter.
When temperatures drop below freezing, the wood frog's vital body cells store more glucose, which acts as an antifreeze. About a third of the remaining body fluid freezes to ice, and the now bloodless organs cease to function. Heartbeat and breathing stop until the frog thaws again next spring. This extremely extreme survival strategy enables the animal, also known as the “ice frog”, to spread northwards over Alaska. The native common frogs, however, find frost-free shelters in holes in the ground or at the bottom of bodies of water, where they can survive ice-free, but in a frozen state with a severely reduced metabolism.


Cold feet, no problem

The feet of penguins, ducks and other Nordic seabirds that are exposed to icy water also have a natural protection against the cold. They never become as clammy and clumsy in the cold as it quickly happens to human fingers in cold surroundings. The difference is that the cell membranes of the cold-adapted bird's feet have a particularly high proportion of unsaturated fats. Human cell membranes have more saturated fats, and these become solid at low temperatures, causing them to lose their suppleness. The nerves and muscles of our fingers therefore lose their functionality below about eight degrees C.
Because their feet are “allowed” to get so cold, the heat loss for the ducks, which often rest for a surprisingly long time on frozen water surfaces, is reduced. They radiate less heat to the environment than would be the case with warm feet. Her blood in the body, which is very well insulated by the plumage, remains warm and only sinks in the feet to almost freezing point. The arteries and veins are closely intertwined in the birds' feet so that they act like a heat exchanger. The blood coming from the body is cooled and the blood flowing back is warmed up.


Keep warmth as best as possible

There are many strategies for surviving the cold winter. Dense fur, a thick layer of fat under the skin, and energy-saving behavior help some mammals to retain heat. Some animals team up in communal shelters with conspecifics who keep each other warm. The honeybees, which overwinter as a whole colony, form a dense winter cluster and, through muscle tremors, manage to keep their outer edge from falling below 10 degrees C. Migratory birds and some flying insects such as the painted lady move to the south. And some shrews can literally shrink a little to curb their constantly high energy needs in winter.

 

Published in: Tierreport No. 4/2013

© E. Wullschleger Schättin