The first job of hunting wolves is to locate their prey, and wolves will travel up to twenty miles (or more) each day in search of food. Wolves have an excellent sense of smell and often locate prey using their noses, although chance encounters often lead wolves to their next meal. Wolves can follow the fresh tracks of animals on the ground, but more often, wind borne odours lead them to their next meal. Wolves can often detect the scent of a prey animal from up to one and a half miles away, if the wind is blowing from the direction of the prey animals towards the wolves. Wolves may sometimes be able to smell the presence of prey animals over even longer distances. In his book, The Wolf: Ecology and Behavior of an Endangered Species, David Mech reported that wolves were able to smell a moose (Alces alces) with calves over a distance of 4.5 miles. Wolves are always alert for signs that prey animals are around. Once they sense that one is near, they approach it quickly, quietly and very cautiously, since they cannot reveal their presence to their prey. If the prey animals pick up the scent of the wolves before the wolves have a chance to attack, then they will run or try to defend themselves. Wolves are quite swift, and can run at speeds of up to 32 kilometers per hour (20 miles). Chases are typically short, as wolves will not attempt to pursue a prey animal if there's little chance that they will capture it. Attempting to chase and kill an animal that would be very difficult to capture would waste the wolves' energy. However, L. David Mech once observed a wolf that chased a deer for roughly 13 miles, so wolves will sometimes pursue a prey animal over long distances. Wolves can run at a speed of 5 miles per hour for several hours, and have become well adapted for running long distances.
Despite the fact that wolves are skillful hunters, they often go days or even weeks without food. It has been estimated by wolf biologists that only about 10% (sometimes this figure is as low as 4%) of a wolf pack's attempts to catch prey are successful. This is because prey animals have many ways to escape from or defend themselves from wolves. Musk oxen (Ovibos moschatus) try to defend themselves from wolves by bunching into a circle with their hindquarters together and their horns pointing towards the wolves. The calves stay in the inside of the circle so the adults can protect them. A kick from the hooves or a lunge from the horns of a musk ox can be fatal to a wolf. Moose often defend themselves by fighting with the wolves, and they often inflict fatal wounds on wolves by kicking with their sharp hooves or lunging with their antlers. Moose that try to fight off an attacking pack of wolves are often successful. Moose may also try to run from wolves, as do deer, which are very swift, or they may retreat to a deep body of water or a fast flowing river. Moose that attempt to flee from wolves are often killed or injured, however, as wolves are usually capable of outrunning a moose. Once wolves catch up to a moose, they start to attack it from the sides and hindquarters. Sometimes, one wolf will attempt to bite onto the muzzle of a moose while the rest of the pack attacks the animal's hindquarters and the sides of its body. Deer, which lack the strength and ferocity of the moose, almost always run from wolves, and they are often capable of outrunning a pack of wolves.
Wolves use a variety of strategies to capture their prey. Arctic wolves may try to provoke a stampede of musk oxen by staring at them, giving them false charges or by nipping at them. A stampede will expose the weak, vulnerable calves which will be attacked by the entire pack. Sometimes, one or two wolves will chase their prey right into another group of wolves. Wolves will also try to run their prey into exhaustion, or they may surround a herd and drive it into the open to expose the weakest animal.
If the wolves do get the chance to attack an animal, they will surround it and bite its neck, rear, head and sides to bring it down. Wolves rarely (if ever) hamstring a prey animal. The cause of death of the prey animal is usually massive blood loss, shock or both, although wolves may snap the neck of a smaller animal. The wolves will immediately start to devour the animal. The rump or hindquarters of the prey animal, as well as the internal organs, are usually the first parts of the prey animal eaten, and the muscle and flesh are usually the last parts eaten. Adult wolves are capable of eating about 14 kilograms (20 pounds) of meat at once, because wolves often go for long periods of time without eating, so once they do get food, they eat as much as they possibly can. If they cannot eat the entire carcass at once, they will often return to it later, if it has not been taken over by bears or other animals. Wolves snarl and snap at each other while they eat, although it is a myth that wolves often kill each other while they feed on a prey animal.