Vast predators are simultaneously in conflict and harmony within the American West. Although wolves tend to overpower cougars and seize their kills, cougars’ transition from elk-centric to deer-rich diets, coupled with a challenging terrain for evasion, may enable cougars to evade perilous wolf confrontations.
Wolves and cougars have returned to Yellowstone over the last 50 years after being hunted to near-extinction.(Image credit: (left) Gary Blatter / 500px via Getty Images; (right) Justin Duffy./Oregon State University via Flickr, CC BY-SA 4.0)Subscribe to our newsletter
Following the reintroduction of wolves to Yellowstone National Park, cougars — who had only recently re-established a presence a few decades prior — were able to coexist due to shifts in their diets and the park’s varied terrain, according to recent findings.
Encounters between wolves (Canis lupus) and cougars (Puma concolor, also referred to as mountain lions and pumas) in Yellowstone National Park occur when wolves pilfer prey from, and occasionally dispatch, cougars. This dynamic becomes more harmonious when cougars subsist on smaller prey, according to a new study published on Jan. 26 in the journal PNAS. The successful coexistence of wolves and cougars in Yellowstone, the research indicates, hinges more on the variety of prey and the availability of escape routes for cougars than on the overall abundance of prey.
“Yellowstone presents a compelling ecosystem as it hosts the complete array of large carnivores and migratory ungulates that North America once possessed,” stated Chris Wilmers, a wildlife ecologist at the University of California, Santa Cruz, who was not involved in the new research, in comments to Live Science. “Many of these species are reappearing –– wolves were reintroduced, and populations of mountain lions and grizzly bears have been recovering –– making it a system that is also in transition. As these populations recuperate, observing their interspecies effects is exceptionally intriguing.”
The territories of cougars and wolves are increasingly converging across the western United States. Throughout the initial half of the 20th century, both species were almost entirely eliminated from the U.S., primarily due to hunting. Cougar populations started to recover in the 1960s under enhanced protections, and wolf reintroduction commenced in the 1990s, benefiting from expanded legal safeguards.
Both species are now widespread throughout the western U.S., yet scientists continue to investigate the population dynamics of these animals and their influence on the broader Yellowstone ecosystem.
The recent study involved an analysis of nine years of GPS data gathered from collared wolves and cougars, supplemented by fieldwork at nearly 4,000 locations across Yellowstone. The investigators discovered that wolves occasionally kill cougars, but cougars do not kill wolves.
These findings are consistent with prior research demonstrating that wolves are the more dominant large carnivore within this food web, despite the two species having comparable body sizes. Wolves likely assert dominance because they operate in packs, whereas cougars are solitary hunters. This pack structure enables wolves to displace cougars and seize their prey, according to lead study author Wesley Binder, a doctoral candidate in the Department of Fisheries, Wildlife, and Conservation Sciences at Oregon State University.
“These encounters are quite one-sided,” Binder informed Live Science. “However, cougars possess the capacity to adapt in certain respects.”
The dietary habits of both cougars and wolves are undergoing changes, as indicated by the new findings. Between 1998 and 2024, elk constituted a decreasing proportion of wolf diets, dropping from 95% to 64%, and for cougar diets, from 80% to 53%. This dietary shift is likely attributable to a general decline in Yellowstone elk (Cervus canadensis) populations.
Researchers placed GPS collars on cougars to track their movements in the national park. (Image credit: Jake Frank, National Park Service)
This decline prompted alterations in wolf and cougar interactions. “If cougars capture larger prey such as elk, this provides wolves with more time to locate the cougar near that kill,” Binder explained. “We observed that wolves and cougars were six times more prone to interact when cougars hunted elk, as opposed to deer. Deer are less than half the size of elk, so cougars consume them considerably faster, leaving wolves with significantly less opportunity to discover those kill sites.”
The shift in cougar diets away from dwindling elk populations resulted in fewer overall encounters with wolves. Instead of elk, cougars began to prey on smaller animals, such as deer. Wolves, the study found, increased their consumption of bison.
“It is crucial to recognize that this is the reason for the cougars’ dietary switch, but by doing so, it rendered them less susceptible to scavenging and potential demise by wolves,” commented Wilmers.
The topography, as revealed by the findings, also influences the animals’ encounters. Cougars experienced fewer perilous encounters with wolves when situated in rugged terrain or near trees they could ascend.
Yellowstone’s varied prey and landscapes appear to create an optimal environment for wolf-cougar coexistence. The populations of both species are presently stable. “Wolves and cougars favor different types of habitat, and Yellowstone possesses diverse terrains that accommodate each of these carnivores,” Binder remarked.
The discoveries illuminate the ideal environmental and prey conditions for the stable coexistence of two large carnivore species, demonstrating how inter-predator conflicts can have a cascading effect throughout the entire ecosystem.
“We are continuously striving to comprehend the impact of large carnivores on prey [populations],” Wilmers stated, “as well as the dynamics of interactions between large carnivores, and how these might either amplify or counteract each other’s influence on prey. … This marks the initial phase in deciphering the narrative of the relationship between wolves and [cougars].”