psychofactz:

http://psychofactz.tumblr.com/

When attacked, the lizards detach their tails and run off. The predator feasts on the lizard tail, and the lizard escapes and grows a new tail. 

This is a trait that appears in several lizard species. This defense mechanism appears in lizard populations that come into contact with poisonous vipers. 
Losing ones tail impairs growth and mobility, so it has little evolutionary advantage. It’s only advantageous when lizards are preyed upon by venomous snakes. When bitten in the tail by a venomous snake, the lizards receive a lethal dose of poison. They need to learn to amputate their own tails in order to save the rest of their bodies.