The Pack (aka The Long Dark Night) (1977)

Storyline

Dogs and man have been together since the prehistoric times. On a trip in the woods, the owners of the dogs would abandon their dogs and leave them in the wild. After about 3 hours of trying to find any means of survival, the dog finds a shed filled with other dogs that were also abandon by humans. Left with no other choice, the dogs resort to cannibalism and form the pack, a pack of abandon dogs out for vengeance. An old man and a kid were the first victims of these beasts. And now, a family staying in the resort must defend themselves against the pack and survive by any means possible