Insulation by Fur and Feathers

There is a strong correlation between the extent of integumentary insulation and the rigors of natural environment. In general, Arctic or Antarctic species are better insulated than tropical species, with well marked seasonal variations in the thickness of fur (example, Polar bear) or feathers (example, penguins).

Likewise, the aquatic mammals living in these areas such as seals and whales have thick layers of subcutaneous blubber (fatty layer) as a means of major insulation. However, it should be noted that the extent of fat deposition (blubber) is not the same in all parts of the body.