Wolves often kill more male ungulates and calves than female adult ungulates. In Banff National Park, a study done by Huggard (1993) found that wolves killed a higher proportion of adult male elk and calves than they occurred in the population. Mech and Nelson (1986) also came up with similar results. They found that adult male white-tailed deer and white-tailed deer fawns were more vulnerable to wolf predation than female deer. It is possible that wolves kill more male deer than female deer because male deer may become weakened after the rutting season and may therefore be more vulnerable to predators. A different explanation has been proposed as to why wolves kill more male elk (Huggard, 1993). In the winter, elk occur in small bull herds or larger cow-calf herds. When wolves come across a herd of all bulls, they have no choice but to attack an adult animal. When they encounter a herd of cows and calves, they will be more likely to attack the weaker, more vulnerable calves, so fewer cows will be killed.
Wolves will also selectively kill older animals over younger (adult) ones. Boyd et al. (1994) found that colonizing wolves in the Glacier National Park area killed older adult animals more often than they killed young adults. The study also found that wolves kill male animals at a relatively high rate relative to their occurrence.
When wild prey animals are scarce, wolves often turn to killing sheep, cattle and other domestic animals for food. Wolves often behave differently when they turn to such animals for food. They sometimes start to consume only part of the animals they kill. Wild cats, such as lions and hyenas also display this behavior. However, wolves rarely kill more animals than they can consume while they hunt wild prey, although such "surplus killing" by wolves has been observed in the wild. DelGiudice (1998) found that wolves will kill white-tailed deer in excess of what they need during severe winters, a time when their prey are generally weak and vulnerable to starvation. Any meat that is not eaten by wolves is usually eaten by foxes, coyotes, weasels or ravens.
Wolves do most of their hunting at night or during dusk or dawn. When pups have just been born, the mother stays with them while the rest of the pack hunts. As soon as the pups are eight to ten weeks old, the pack moves to an area (the rendezvous site) within its territory which acts as a meeting place for the pack members and as a place for the pups to stay. A lower ranking wolf will look after the pups while the other adults go hunting for food each night. Large pieces of meat are often stored at cache sites, which are located near the den. Such caches are often dug up by foxes or weasels.
