Why can gray wolves sometimes kill livestock?

Gray wolves may kill livestock when they have the opportunity to do so. While their primary diet consists of large herbivores such as deer, elk, and moose, wolves are opportunistic predators.12

In some regions, particularly where natural prey is scarce, wolves may survive by consuming livestock, livestock carrion, and human garbage. Despite this, many wolves that live in proximity to livestock rarely or never attack them. While the number of livestock killed by wolves in North America remains relatively small, these incidents have increased as wolf populations expand their range.12