Adaptation

"Weasels, at first glance, seem to be designed wrongly. They are beautifully camouflaged in white, yet that conspicuous black tip of a tail seems an odd, inexplicable anomaly--until experiments showed that hawks easily captured fake weasels that had no black tipped tail. When the hawks were baited with fakes that had black tipped tails, however, the birds grew confused, either momentarily hesitating or attacking the tails as though they were the head- end. Other small animals also use deception-evolved tails. Many lizards, for example, have colorful, conspicuous tails that divert or distract predators. The tail is easily detachable, and starts writhing and flailing after being detached to divert the predator even more from the live whole animal that slinks away. Lycaenid butterflies also have similarly distracting and detachable "tails" on their wings that fake out a predator in much the same way a good basketball passer fools his opponent on the court. The butterflies' tails imply to a predator that its prey is about to head in one direction, when it then turns and escapes in the opposite."

Bernd Heinrich , Winter World, The Ingenuity of Animal Survival, Harper Collins, 2003, p. 48