I NEED HELP! please folks i need to find a book that i cant remember its name!?

there is this horror book that i cant remember its name...but i'll try to sum it up... it was about a boy who found a grave that said "do not dig" and the by dug anyway and found a bird-lizard like creature and kept it as a pet which eventually ate his bird and his dog at night so the boy tried putting it back to its grave but it just kept cumming. Please Help?