As elk migration patterns shift with changing environmental and anthropogenic conditions, some wolf packs in Wyoming are doing something never before documented in this region: moving their young pups miles across difficult terrain to track their prey.
A new study published in the journal Current Biology reveals flexibility in wolf behavior: some packs are not only adjusting their own seasonal movements to follow migratory elk, but even moving dens — previously thought to anchor packs in place — along migration routes and in some cases into elk summer ranges. The findings challenge widespread assumptions about wolf behavior and highlight the ripple effects climate change may have across predator-prey dynamics.
“These wolves are migrating,” said wildlife biologist Avery Shawler, who coauthored the August paper. “They’re using different areas in the winter and summer and there is some evidence that they might be doing that to track their prey. We have collar data that shows that winter and summer range don’t overlap at all, and that is the definition of migratory.”
Shawler told Mountain Journal that the research was initially part of a predation study examining kill sites to see what wolves were eating. Researchers collared wolves following the Cody elk herd outside of Cody, Wyoming, in the eastern Greater Yellowstone Ecosystem. As part of that study, the team outfitted both wolves and elk with collars to gather simultaneous GPS information for both predators and prey.
“As we collected data from multiple years of GPS collar data and started doing movement analyses, we found that wolf packs in the area had different movement strategies to track elk,” Shawler said.
The team, including Kenneth Mills, lead wolf biologist for Wyoming Game and Fish, collared nearly 100 cow elk between 2019 and 2020. The herd is large — between 6,000 and 7,000 elk — and wolves are distributed across their range within different territories.
Mills said Game and Fish consistently implements an adaptive management framework while making supervisory decisions for wolves in northwest Wyoming. “Any new information garnered through this and similar studies can be integrated into species management of wolves,” he said.
Mills and other large carnivore biologists with Fish and Game in the area had already documented wolf packs moving pups long distances from their dens through trail cameras and field monitoring. However, Shawler said the elk and wolf GPS collar data from this study provided clearer evidence that wolf movements were closely tied to the timing and routes of elk migrations.
“These wolves are migrating. They’re using different areas in the winter and summer and there is some evidence that they might be doing that to track their prey.
Avery Shawler, wildlife biologist, coauthor
She said the findings show that wolf packs in the area use a variety of movement strategies to follow different groups within the partially migratory Cody elk herd — an elk herd with both short and long-distance migrants as well as elk that don’t migrate, similar to most in the Greater Yellowstone Ecosystem. The collar data showed that some wolf packs tracked elk that migrated only short distances, remaining near their den sites. Others followed long-distance migrants, relocating their homesites and even moving young pups to follow these elk along their migration route and into summer ranges.
“A lot of elk in the Greater Yellowstone are partially migratory,” Shawler said. “Some migrate and some don’t. The Cody elk herd is partially migratory, and we found that wolf packs in the area track different subpopulations within that herd.”
Shawler worked closely with Arthur Middleton, another coauthor of the paper and a lead researcher in ungulate migration strategies. Middleton’s research shows how migratory elk use climate cues such as melting snow or greening grass to determine the timing and speed of their migrations.
The research team also included Tony W. Mong from Wyoming Game and Fish; Kristin J. Barker of the University of California-Berkeley and the Beyond Yellowstone Living Lab; and Wenjing Xu of Germany’s Senckenberg Biodiversity and Climate Research Centre.
Shawler said that because environmental conditions are unpredictable, elk migration is fickle, and wolves are finding strategies to adjust to that. “The research sheds light on what wolves are doing outside of protected areas,” she said. “A lot of what we know about wolves in the West is from studies based in Yellowstone, and most wolves in the western U.S. live outside of protected areas and face different levels of human presence.”
Moving dens is risky for wolves, especially in places where neighboring wolf packs are closer together lending to a higher population density in the area. The leading cause of mortality for wolves, at least in Yellowstone National Park where they are protected, is other wolves. And the easiest way for wolves to kill other wolves is to eliminate their pups, so pup mortality from other packs is a major risk when moving homesites. Shawler said this is one reason why wolves normally establish den sites in elk winter ranges and remain there throughout the season while the pups are young.
But she said that outside the park, and where packs are more dispersed, wolves are waiting for elk to begin migrating, then moving pups who are too young to walk on their own to a new den. In at least one documented case, GPS data showed a wolf moving its pups up to 13 miles across rugged terrain.
“We observed two packs shifting their pups multiple times, often along migratory routes and within elk summer range or close to it,” she said.
The department’s wolf monitoring program tracks how wolf packs move and behave throughout the year, revealing how their patterns shift with northwest Wyoming’s changing ecological conditions such as green-up timing, the period when winter ends and new vegetation starts sprouting. Mills said the study confirmed what biologists are seeing on the landscape.
“We believed this diversity is primarily linked to prey availability, which is largely influenced by elk migration,” Mills said. “However, this research was important in showing a quantitative framework that demonstrated the movements were, in fact, linked to migratory elk movements.”
