Not all mammals have fur; animals without fur may be referred to as "naked," as in "naked mole rat."
The two-toed sloth can seem to have green fur, but this color is caused by algal growths.
There also are breeds of cats, dogs, and mice bred to have little or no visible fur.
A Polar bear's coat has two layers of hair: an outer layer, made up of long (5-15cm) guard hairs; and a thick undercoat, made up of shorter hair. These guard hairs are mostly transparent or clear, but thanks to some special characteristics that work to create cool optical tricks, these hairs appear white.Nov 2, 2012
Believe it or not, their hair isn't actually white! Their long outer hairs, which protect their soft, thick undercoat, are mostly hollow and transparent. The thinner hairs of their undercoat are also colorless. Polar bear hair looks white because the air spaces in the hairs scatter light of all colors.
But otters are able to keep their sleek, adorable figure thanks to their incredibly dense fur. They grow over 1,000,000 hairs per square inch! ... Although it feels smooth to the touch, it's actually like a miniature Velcro suit, full of hooks and barbs to lock the hairs together and make them as snarled as possible.Jan 28, 2016