According to Pokedex entries: Heatmor eat Durant by burning his outer coat and then sucking out his body fluids. In the series, a Pidgey tries to eat a Caterpie. From these facts, you can say that it really depends on witch animal the Pokemon is based off of. Because this is a game that is rate E (10+ in some cases), GameFreak decided not to show Pokemon, well, "EATING" each other. If they did show Pokemon eating other Pokemon, then that would completely destroy the system of Pokemon fainting.