Trophic cascade wolves1/14/2024 ![]() Grizzly bears and mountain lions, which also prey on elk, increased due to more protections from states and the federal government. Then, between 19, wildlife officials reintroduced 41 wolves to Yellowstone. For the next several decades, elk cycled through population booms and collapses along with climate fluctuations hard winters left the ground littered with hundreds of the carcasses of elk that had starved to death. When the park stopped killing elk in 1968, numbers shot up again from about 5,000 to close to 20,000. National Park Service and the state of Montana removed more than 70,000 elk from the Northern Yellowstone herd by killing them or shipping them across the country to areas where they’d been eliminated. ![]() With the wolves gone, and bears and lions greatly diminished, elk populations skyrocketed. ( Read more about the history of Yellowstone National Park.) The last known Yellowstone wolf pack was killed in 1926, and the canines were also wiped out in most of their historic range in much of the lower 48, hanging on in a few populations around the Great Lakes. Before the 1900s, Yellowstone predators such as grizzly bears, black bears, wolves, and mountain lions thrived alongside robust populations of American bison, elk, mule deer, pronghorn, and bighorn sheep.īut a coordinated campaign by the federal government exterminated almost all those predators, and bison, from the area. This is especially useful for managing and conserving wolves, which are still rebuilding their numbers after over a century of persecution. Synthesizing all of that data revealed that wolves target bulls during years when vegetation is poor, offering a clearer understanding of how shifts in climate can change predators’ behaviors. The team then used satellite data to derive how much plant life was available for elk to eat each year, an amount dependent on snowmelt and rainfall. The scientists spent about a month at the beginning and end of each winter tracking three wolf packs, locating every elk kill the wolves made recording the dead animal’s age and sex and removing a bone marrow sample, which determined the elk’s physical condition before death. Finding a balanceįor their study, Wilmers, Smith, and colleagues analyzed more than a thousand dead elk in Yellowstone-located in the states of Wyoming, Montana, and Idaho-over 20 years. The findings in Yellowstone are also relevant, he adds, as Coloradans vote in November whether to reintroduce wolves to their state, home to about 287,000 elk-the largest number in the U.S. Through hunting and management practices, “humans help stabilize elk populations, but they don’t do the same thing as wolves.” “In a future that will be very unpredictable, we want a buffer” against mass die-offs, says Doug Smith, Yellowstone’s senior wildlife biologist, and wolves’ ability to keep elk herds balanced can play that role. ![]() For instance, elk herds that maintain consistent numbers, rather than yo-yoing up and down, can better withstand more frequent droughts-one impact of climate change that is already occurring in the region. ( Explore the Yellowstone most don’t see.)īut most importantly, the Yellowstone area’s wolves-which now number between 300 and 350-could help elk herds weather the perils of a more volatile climate, according to the study, published in the Journal of Animal Ecology. ![]() So by targeting bulls during years of scarce food, they give the cows a chance to reproduce, thus keeping the population afloat. In dry years, they’re even more diminished.Īs adaptable, intelligent predators, wolves have learned to recognize these conditions, and they would rather kill an undernourished 750-pound bull versus a 450-pound cow. All that effort burns calories, weakening them heading into winter. These burly males already don’t eat much in the fall, focusing instead on making deafening bugles and smashing into each other while fighting over cows. But Wilmers led a recent study that showed during particularly dry years-when grass, shrubs, and wildflowers aren’t as lush-wolves switch to hunting bulls. “Elk aren’t starving to death anymore,” says Chris Wilmers, a wildlife ecologist at the University of California, Santa Cruz.ĭuring years with normal amounts of rain and snow, wolves primarily kill older cow elk, since they’re the easiest to hunt. New research shows that by reducing populations and thinning out weak and sick animals, wolves are helping create more resilient elk herds.įor the past 12 years, elk numbers in the park’s largest herd have leveled off between about 6,000 and 8,000, instead of extreme boom-and-bust cycles due to climate fluctuations. Laramie, WyomingTwenty-five years after gray wolves returned to Yellowstone National Park, the predators that some feared would wipe out elk have instead proved to be more of a stabilizing force.
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