Wolves move pups across mountains to adapt to climate pressure

Gray wolf pups normally spend their first weeks tucked safely inside a den, eyes and ears still sealed, with none of the keen senses that will define them as adults.

So when biologists set remote cameras on the slopes east of Yellowstone National Park and later scrolled through the images, they were astonished: adult wolves padding across steep, snow-dusted ridges with tiny pups dangling awkwardly from their jaws.

“The first time I saw a camera-trap photo of a wolf carrying its pup, I just cracked up because the pup is being carried by its butt,” recalled lead author Avery Shawler, who recently completed her doctorate at the University of California, Berkeley. “You can picture a squirming child and the mom just being like, ‘All right, we’re doing this.’”

Long, risky moves with wolf pups

That lighthearted moment led to a serious discovery. Shawler and colleagues paired thousands of GPS locations from 19 radio-collared wolves with the movements of ninety-nine elk.

The team documented something never seen outside of the Arctic: packs taking long, risky journeys during pup-rearing season to shadow migrating prey.

Adult wolves sometimes commuted tens of miles from their dens to temporary hunting grounds. They sometimes moved entire litters over 12 miles to new sites closer to vulnerable newborn elk calves.

Wolves climb to hunt elk

The Greater Yellowstone Ecosystem hosts tens of thousands of elk, many of which leave low valleys each spring for higher, greener meadows. The ascents vary. Some herds wander only a few miles; others climb 50 or more. When the elk went far, certain wolf packs did too.

“Our findings counter years of assumptions that migratory hoofed mammals can escape predation in spring because [their predators] are tied to dens and immobile offspring,” said senior author Arthur Middleton, a Berkeley wildlife ecologist who spent a decade tracking elk and their predators.

The data show that wolves are anything but immobile: they adapt their route, pace, and even nursery locations to keep elk within striking range.

Lugging pups through the mountains

GPS fixes revealed three broad strategies. Packs whose local elk stayed put also remained near original den sites, defending territories of roughly 15 square miles.

Others made what Shawler calls “commutes” – out-and-back forays of six to 12 miles that allowed adults to hunt migrating elk for a few days before returning to feed pups.

But the boldest tactic was true migration: entire packs shifted home ranges for weeks, lugging weeks-old pups through mountain passes in May or early June.

Moving wolf pups is dangerous

Moving infants is dangerous for any carnivore, but especially for wolves, which face lethal clashes with neighboring packs.

“In Yellowstone, research has shown how a lot of wolf mortality can come from other packs coming in and killing pups, because there’s a lot of packs competing for space and food,” Shawler said. “It’s pretty wild that this risky behavior of moving young pups is even occurring when that’s happening next door.”

Why gamble? Elk calves provide calorie-dense meals just when lactating females and growing pups need them most.

Climate change, however, is scrambling the timing of that resource. Earlier studies from Middleton’s lab show that elk now arrive on winter ranges as much as 50 days later than they did at the turn of the millennium, which lengthens the spring migration.

Wolves apparently respond by prolonging their migration patterns too, refusing to let dinner disappear over the horizon.

Ranchers may face more wolf risks

More than five hundred wolves now roam the Yellowstone region, and many spend part of the year beyond park borders where cattle and sheep graze. Understanding when and where packs migrate could help ranchers anticipate predation risk.

“Our research provides some insight into the behavior of wolves living on working landscapes and how they’ve had to adapt to an environment that is different from what wolves were dealing with 100 years ago,” Shawler noted.

That insight is timely for California, where wolves recolonized in 2011 and now number perhaps a hundred across ten packs. Middleton, who co-leads the new California Wolf Project, said the lessons from Yellowstone are shaping questions farther west.

“While it’s still early days, our partners in California have a strong hunch that the numbers and movements of deer and elk are playing into wolf behavior, including livestock predation,” he explained. “The work around Yellowstone sharpens our ideas and approaches as we grow the project in California.”

Climate change alters migration patterns

Both prey and predator are feeling the pressure of a warming, busier West. Earlier snowmelt and altered plant growth tug elk migration schedules in new directions, while expanding human settlement fragments habitat. Wolves reveal that cascade in real time.

Their bold pup-carrying journeys are, in Middleton’s words, “a moving barometer of ecosystem change.”

For Shawler, the discovery also carries a note of wonder. Each blurred camera-trap frame of a mother wolf trotting uphill with a pup clamped gently in her jaws speaks to resilience. It also reveals the deep ecological choreography linking large carnivores with the great migrations of the hoofed animals they hunt.

The study is published in the journal Current Biology.

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