I know that some snakes kill other snakes and eat them and some same specied fish probably eat each other.... For the snake I think it was a King Snake???? Not so sure though.....
Any meat-eating animal will eat the flesh of a dead member of its own species if it is starving, just as humans would. Or some other basic animals would be snakes and fish.
A cannibal this is what i know them as anyway I'm presuming you're referring to creatures such as the black widow spider (where the female eats the male) or cats (where parents eat their young)