How Animals  Survive Cold Conditions
Science of the Cold

One of the commonest questions asked about animals in Antarctica is how do they cope with the extreme cold conditions that are found there?

Air temperatures averaging below freezing over the year (frequently significantly below freezing) with a range in many places around  -40°C to +10°C and highs up to +22°C amongst rocks and moss banks, though many places are significantly colder. The sea temperature varies from -2°C to +2°C over the year.

Antarctic birds and mammals - penguins, whales and seals - are warm blooded animals and they maintain similar internal body temperatures to warm blooded animals in any other climate zone - that is 35-42°C (95-107°F) depending on the species. They have to keep high body temperatures to remain active. These animals are known as endotherms (endo-inside + therm-heat) as they generate their heat internally. Antarctica's cold and wind mean that this heat can very quickly be lost leading to hypothermia (hypo-under).

Many animals are ectotherms (ecto-outside) , which means that they generate so little heat internally they are dependent on the external environment to warm them up to a level where their enzymes function sufficiently well for an active and functional life. Typically they raise their temperature by basking in the sun until they are warm enough to become active. Reptiles and amphibians do this while many invertebrates are small enough to be able to warm up quickly to the ambient temperature from the air alone without basking in direct sunlight.

A large ectothermic Antarctic land animal would never get enough energy regularly enough from the surroundings to become sufficiently active once it had cooled. All Antarctic land animals of any size therefore need to be warm-blooded to be active. Antarctica is such an extreme environment that the size limit for an ectotherm is about 1mm, the size of the largest fully terrestrial (land) animal in Antarctica. In other words any animal larger than this would not be able to warm up enough to become active before it started to get cold again.

Antarctica is a land mass surrounded by a large very cold ocean,

• All - Most of all you need to be large to reduce the loss of heat from your skin.
• All - Extremities tend to be small to prevent undue heat loss.
• All - You need to be well insulated, internally immediately under the skin with stored fat (blubber) and externally with fur (the best insulation of all, though useless when wet) or feathers.
• All - Eat lots of high energy easy to digest food to keep warm from within. All large animals (from the smallest birds upwards) in Antarctica are carnivores. Meat is a more concentrated energy rich source of food than is vegetable matter that doesn't grow very well or very widely in Antarctica anyway. Food supply is more of a problem than the other aspects of living in a cold climate, small animals cannot eat enough to keep warm in extreme cold.
  
  
• Some - Huddling together in large or small groups is a good way of getting protection from the wind and retaining warmth.
• Some - Whales - never leave the sea, so little exposure to extremes of air temperature, then migrating north when the air temperature drops enough to start making the sea freeze.
• Some - Seals - entering the sea at times of extremely cold air temperatures and high winds, then migrating north when the air temperature drops enough to start making the sea freeze.
• Some - countercurrent heat exchangers in seals and whales flippers and birds feet means that these parts are kept at a lower temperature than the rest of the body to reduce heat loss.

More about how penguins stay warm in the cold.