The Open Door Web Site : Biology : When the Climate is Too Cold for Animals to Remain Active

Animals can be found all over the world at almost any temperature. "Warm-blooded" animals will insulate their bodies in the cold and consume energy-giving food to stay warns. "Cold-blooded" animals will warm themselves up by basking in the sun.

Cold climates affect different animals in different ways. Usually it is the small animals that find it hardest to survive in a cold climate. The bodies of small animals lose heat more quickly than the bodies of large animals. It should also be noted that the bodies of small animals warm up more quickly than the bodies of large animals. In winter outside the tropics the sun's energy is weaker and the air stays cold all day. What happens to these animals in winter?

Comma butterfly © Paul Billiet

The comma butterfly looks like a dead leaf when its wings are folded. In this way it can hide on the branch of a tree during winter.

"Cold-blooded animals" in winter.

Larger "cold-blooded" animals, such as lizards and frogs, find their bodies becoming colder and colder as winter approaches. They become sleepy and, eventually, totally inactive. This state is called torpor, or we say "these animals have become torpid". Torpor is similar to sleep except that every part of the body slows down. In torpid animals the heart beats slowly, the lungs almost stop breathing and the body temperature falls.

These animals must not let their bodies freeze solid because this would kill them, so before winter starts, animals such as frogs and snakes try to find a place which is protected from freezing temperatures. Frogs will bury themselves in the mud at the bottom of streams or ponds. Lizards and snakes will burrow down into the earth. Even in a hard winter, only the surface of a pond will freeze. The mud at the bottom of the pond will remain a few degrees above freezing point.