http://tvblogs.nationalgeographic.com/2013/04/10/zombie-snake-attack/
unlike mammals, reptile reflexes remain deadly after death. In fact, they can still bite and deliver a killing dose of venom up to an hour after being decapitated. And after Thomas delivered what he thought was a deadly blow, the snake’s head–severed from its body–continued to scan the area, waiting for an opportunity to strike: