I have a 3month old patterdale terrier and when i take put walking she try's to eat sheep sh** i have stopped her eating it while shes on the lead but when shes off she will pick it up and run off and eat it and runs away when i get close to her, also when she finds bird sh** she will roll in it. Why is she doing these things and any suggestions to how i stop them no so botherd about the bird sh** thing but would like to know why she does it