Well, the practice of eating faeces or dung has a term for it- coprophagia. Some animals eat excrement both their own and that of others. Dung beetles, rabbits, chimpanzees and domestic dogs are some. Most of them do it because the poop contains some undigested food containing vital nutrients. The small intestines of these animals are unable to absorb everything the first time. So they take in the nutrients a second time. Chimps don’t do it as regularly as rabbits, and dung beetles eat other animals’. Worms and parasites can also cause a dog to eat its own poop.