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A typical wolf pack comprises of a breeding pair and their offspring, including both young and mature wolves that haven’t yet set out on their own.
A wolf pack is essentially a family, says Doug Smith, a wildlife biologist who headed the program to reintroduce wolves to Yellowstone and launched the Yellowstone Wolf Project, an initiative that, over the years, has produced an extensive body of research on wolves.
Despite common images of wolves as ruthless and vicious, wolf families are primarily functional. Wolves in a pack work together, play together and take care of each other when they’re ill or injured. Wolves are especially devoted to their young. The entire pack helps care for the pups, explains Smith.
When the pups are young, older wolves bring food back to the base camp for the little ones to eat. In the spring, when pups are born, prolactin — a hormone that triggers caregiving — increases for all the pack members, explains Kira Cassidy, a wildlife biologist who studies pack behavior with the Yellowstone Wolf Project. That creates what she calls a “compulsion” to bring food to the pups and the lactating mothers who can’t yet leave the youngest members of the pack.
(Credit:Bildagentur Zoonar GmbH/Shutterstock)
When they don’t have food to bring back, wolves bring toys — feathers, bones, skins of dead animals — for the little ones to play with. Cassidy recalls seeing an adult bring an orange traffic cone to the den for the pups.
Outside of family units, however, the lives of wolves can get rough. Wolves are very territorial, and fighting between packs can be deadly. In areas where wolves are protected from humans, the leading cause of wolf mortality is other wolves, says Smith.
But when humans kill wolves, those deaths can cause more damage than just reducing the population of wolves. In a recent study, Cassidy, Smith, and colleagues found that packs in which humans killed pack leaders were more likely to disband within the biological year than were packs that hadn’t suffered such losses. The study, published in February 2023 in the journal Frontiers in Ecology and the Environment, analyzed 118 years’ worth of data from five national parks.
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The reasons for the devastating effects of losing a pack leader are pretty clear. “When you realize that packs live in these family groups,” says Cassidy, “you understand how it would be like losing a mother or father.”
She points out that the pack can stay together after losing one of the pups, even an older one. But losing a leader is different. Wolves learn from older pack mates. According to Cassidy, leaders teach younger wolves what prey is appropriate to hunt, how to avoid roads and most of the things they need to know to survive. The younger wolves don’t get that training if the pack loses its leader.
The five-park study did not compare human-caused mortality with wolf-on-wolf mortality, says Joseph Bump, one of the study’s authors as well as one of the founders of the University of Minnesota’s Voyageurs Wolf Project. “We need to keep asking the question, ’Is human disruption of packs different from other causes of disruption?’ Because causes of mortality that don’t involve humans might affect packs in very much the same way,” he says.
Still, there are reasons to think that human-caused mortality could have a greater effect if for no other reason than that humans are likely to kill bigger, more experienced wolves. “Hunters choose the biggest wolves to shoot,” says Smith. “That’s usually an adult male, an older, wiser wolf who has survived some battles.” And those wolves, remember, are the ones who teach the younger ones how and what to hunt.
Though there’s not a lot of data on this, it’s possible that pack disruptions due to the loss of a leader could potentially exacerbate conflicts with humans. “There are wolf packs that have access to cattle and sheep but don’t prey on them,” Bump says. He asks us to imagine that the pack loses an individual that makes 40 percent of the pack’s kills. The resulting food stress might cause surviving pack members to begin preying on domestic animals.
Another scenario Bump describes is a pack that loses an older, experienced member who was good at pack-to-pack interactions. The loss of this wolf could mean the pack loses territory and is pushed into areas with less prey and, perhaps, more humans and their livestock.
The results of wolves being killed, at the hands of humans or otherwise, are complex. But one thing is clear: If we are going to understand how to protect wolves and coexist with them, we need to understand how our actions affect wolves at the pack level, not just the population level. We need to get to know the family.
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