There is a breed of gerbil, common around the southern parts of Africa who have the most interesting evolved defense mechanisms. This species of gerbil has teeth that have evolved to be so durable that in the winter they have been seen to burrow straight into the sides of trees, or through wooden walls of houses to escape the cold and predators. They do this primarily from them using the top two teeth like a can opener, the using their strength to pull backwards allowing chunks of wood to be dislodged