Most healthy ungulates are fast enough to outrun a pack of wolves. In fact, fewer than one out of ten attempts to chase moose actually end in a successful kill. If they start to fall behind, the pack will usually give up the chase. If the chosen prey is injured, weakened, or old, however, the wolves can usually catch up with them and attack. This practice is simply too dangerous for the wolf, because to bite the leg, the wolves risk getting kicked in the face by the animal's sharp hooves.
Wolves tend to concentrate on the neck, shoulders, and sides instead.
Wolves' digestive systems operate somewhat differently than ours. They are adapted to process huge amounts of food at a time, then eat nothing for three days or more. Biologist David Mech witnessed a pack of 15 wolves kill a 600- pound moose and eat about half of it in an hour and a half, meat, bones, fur and all. They don't do much chewing, mostly just tearing chunks off and swallowing them whole. After eating their fill, wolves will either spend a few hours relaxing and digesting, or return to the den to regurgitate food for the pups and other pack members who did not join in the hunt.