<Tr> <Td> 1924--1935 </Td> <Td> 0 </Td> </Tr> <P> Updated research in the 1980s verified that the last official killing of wolves in the park took place in 1926 when two pups found near Soda Butte Creek were killed by park rangers . The last reported wolf killed in the Greater Yellowstone Ecosystem (prior to today's legal hunting or control measures) occurred in May 1943 when Leo Cottenoir, a Native American sheepheader on the Wind River Reservation shot a wolf near the southern border of the park . </P> <P> Once the wolves were gone, elk populations began to rise . Over the next few years conditions of Yellowstone National Park declined drastically . A team of scientists visiting Yellowstone in 1929 and 1933 reported, "The range was in deplorable conditions when we first saw it, and its deterioration has been progressing steadily since then ." By this time many biologists were worried about eroding land and plants dying off . The elk were multiplying inside the park and deciduous, woody species such as aspen and cottonwood suffered from overgrazing . The park service started trapping and moving the elk and, when that was not effective, killing them . Elk population control methods continued for more than 30 years . Elk control prevented further degradation of the range, but didn't improve its overall condition . At times, people would mention bringing wolves back to Yellowstone to help control the elk population . Yellowstone's managers were not eager to bring back wolves, especially after so successfully extirpating them from the park . Elk control continued into the 1960s . In the late 1960s, local hunters began to complain to their congressmen that there were too few elk, and the congressmen threatened to stop funding Yellowstone . Killing elk was given up as control method which allowed elk populations to again rise . As elk populations rose, the quality of the range decreased affecting many other animals . Without wolves, coyote populations increased dramatically which adversely impacted the pronghorn antelope population . However, it was the overly large elk populations that caused the most profound changes to the ecosystem of Yellowstone with the absence of wolves . </P> <P> The campaign to restore the gray wolf in Yellowstone had its roots in a number of seminal studies related to the predator - prey ecology of the park . In 1940 Adolph Murie published Ecology of the Coyote in the Yellowstone National Park . That study and his 1940--41 work The Wolves of Mount McKinley was instrumental in building a scientific foundation for wolf conservation . In 1944, noted wildlife biologist Aldo Leopold, once an avid predator control advocate, made the following comments in his review of The Wolves of North America, Young and Goldman, 1944: </P>

What happened when wolves were removed from yellowstone
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