The wolf pack is often pictured as the model of cooperative hunting, but not all gray wolves (Canis lupus) work together to bring down their prey. Some are freeloaders, according to a paper published today in Behavioral Ecology. Researchers studying wolf packs in Yellowstone National Park have found that the group's kill success rate does not increase as the number of wolves grows; instead, it levels off once there are more than four wolves. That seems to be because larger packs include freeloaders, which are almost always those wolves that aren't breeding and thus don't need to risk their lives to feed pups. The freeloading wolves may appear to be cooperating, but they actually do very little until the kill is made, say the authors. In that way, they're like members of a large family joining together for a Sunday dinner—most of whom show up to eat, but don't bring home the bacon.
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