The Crotalid's head is dominated by its ferocious jaws filled with serrated rows of triangular teeth. These teeth never stop growing throughout a Crotalid's life and Crotalid feeding grounds can be easily identified by the gnawed rocks and tree trunks found in the vicinity. Despite this, instances have been reported of dead Crotalids that were killed by their teeth growing so long that they finally pierced the creatures' own tiny brains. Aside from such examples of autophagia, Crotalids are protected by thick scales and a rudimentary nervous system that makes them extremely difficult to kill outright. Once injured or exposed to the scent of blood, Crotalids enter a kind of feeding frenzy which overrides any kind of pain or fear response, sending them into a berserk attack of thrashing limb