After wolves were reintroduced to Yellowstone National Park, cougars, which only regained a foothold decades ago, were able to coexist thanks to a change in diet and the park’s varied landscape, according to a new study.
Encounters between wolves (Canis lupus) and cougars (also known as puma concolor, mountain lion and mountain lion) in Yellowstone National Park occur when wolves steal and sometimes kill prey from cougars, but this dynamic becomes more harmonious as cougars eat smaller prey, according to a new study published Jan. 26 in the journal PNAS. The results of this study suggest that the successful coexistence of wolves and cougars in Yellowstone depends more on prey diversity and the availability of cougar refuges than on overall prey abundance.
“Yellowstone is an attractive system because it has a good population of large carnivores and migratory ungulates that once lived in North America,” Chris Wilmers, a wildlife ecologist at the University of California, Santa Cruz, who was not involved in the study, told Live Science. “Many of these species are coming back. Wolves are being reintroduced, mountain lion and grizzly bear populations are recovering. So this system is also in flux. It will be very interesting to see the impact these species have on each other as these populations recover.”
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In the western United States, cougar and wolf habitats increasingly overlap. Throughout the first half of the 20th century, both species were nearly extirpated from the United States, primarily due to hunting. Cougar populations began to recover under new protections in the 1960s, and wolf reintroductions began in the 1990s and benefited from expanded legal protections.
Both species are now widespread throughout the western United States, but scientists are still studying them to understand the animals’ population dynamics and their impact on the broader Yellowstone ecosystem.
The new study combined nine years of GPS data from collared wolves and cougars with field observations from about 4,000 locations across Yellowstone. Researchers found that wolves sometimes kill cougars, but cougars do not kill wolves.
These findings are consistent with previous studies showing that wolves are the more dominant large carnivores in this food chain, despite the two species’ similar body sizes. Wolves travel in packs and are likely to be dominant, while cougars are solitary, meaning wolves could chase them away and steal their prey, said study lead author Wesley Binder, a doctoral student in Oregon State University’s Department of Fisheries, Wildlife and Conservation Sciences.
“These interactions are very one-sided,” Binder told Live Science. “But cougars have the ability to adapt in a way.”
The diets of both cougars and wolves are changing, according to new research. Between 1998 and 2024, elk went from 95% to 64% of the wolf diet and from 80% to 53% of the cougar diet, likely due to broader declines in the Yellowstone moose (Cervus canadensis) population.
This decline has led to changes in wolf-cougar interactions. “If a cougar kills a large prey like a moose, the wolves have more time to find the cougar sitting on the prey,” Binder said. “We found that when cougars kill elk, wolves and cougars are six times more likely to interact than deer. Because deer are less than half the size of elk, cougars eat it much faster, and wolves have much less of a chance of discovering those kill sites.”
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Changes in cougar diets from declining moose numbers have led to an overall decrease in interactions with wolves. Instead of elk, cougars now eat smaller prey such as deer. They discovered that the wolves started eating more bison.
“It’s important to understand that that’s why the cougars made the switch, but doing so made them vulnerable to scavenging and potentially being killed by wolves,” Wilmers said.
Research shows that terrain also shapes animal encounters. Cougars have fewer dangerous encounters with wolves if they are surrounded by rugged terrain and trees they can climb.
Yellowstone’s prey and landscape diversity appears to be a perfect location for wolves and cougars to coexist. Populations of both species are currently stable. “Wolves and cougars prefer different habitats, and Yellowstone has different habitats that are suitable for each carnivore,” Binder said.
The findings reveal the ideal landscape and prey characteristics for stable coexistence of two large carnivore species, and how conflicts between predators can have ripple effects throughout the ecosystem.
“We are always trying to understand how large carnivores affect their prey. [populations]”And what kind of interactions exist between large carnivores, and how do they combine or cancel out each other’s influence on prey? … This is the beginning of unraveling the story between wolves and wolves.” [cougars]. ”
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