Grey Wolves In Yellowstone Park

Categories: Wildlife


Though they were once brought to near extinction, the successes of the story of the grey wolf are no better viewed than in Yellowstone where visitors, naturalists, park employees, rangers, and their cameras all seek out the natural beauty. In 1872, Yellowstone National Park was created, there was yet no legal protection for wildlife in the park. In the early years of the park, administrators, hunters and tourists were essentially free to kill any game or predator they came across. The gray wolf was especially vulnerable to this wanton killing because it was generally considered an undesirable predator and was being willingly extirpated throughout its North American range. In January 1883, the Secretary of the Interior issued regulations prohibiting hunting of most park animals, but the regulations did not apply to wolves, coyotes, bears, mountain lions and other small predators.[1]

Shortly after the U.S. Army took over administration of the park on August 20, 1886, Captain Moses Harris, the first military superintendent, banned public hunting of any wildlife and any predator control was to be left to the park's administration.[2] Official records show however, that the U.S. Army did not begin killing any wolves until 1914.[3]

In 1885, Congress created the Division of Economic Ornithology and Mammalogy with the express purpose of research for the protection of wildlife. The agency soon became the U.S. Biological Survey which was the forerunner of the U.S. Fish and Wildlife Service. In 1907, under political pressure from the western cattle and livestock industries, this agency began a concerted program which eventually was called: Animal Damage Control. This predator control program alone killed 1,800 wolves and 23,000 coyotes in 39 U.S. National Forests in 1907.[3] In 1916, when the National Park Service was created, its enabling legislation included words that authorized the Secretary of the Interior to "provide in his discretion for the destruction of such animals and of such plant life as may be detrimental to the use of said parks, monuments and reservations".[3]

It is generally accepted that sustainable gray wolf packs had been extirpated from Yellowstone National Park by 1926,[1] although the National Park Service maintained its policies of predator control in the park until 1933.[3]However, a 1975–77 National Park Service sponsored study revealed that during the period 1927 to 1977, there were several hundred probable sightings of wolves in the park.[4] Between 1977 and the re-introduction in 1995, there were additional reliable sightings of wolves in the park, most believed to be singles or pairs transiting the region.[5]

Initial releases 1995–96 

First wolves being transported into Yellowstone for release-January 1995

In January 1995, U.S. and Canadian wildlife officials captured 14 wolves from multiple packs east of Jasper National Park, near Hinton, Alberta, Canada. These wolves arrived in Yellowstone in two shipments—January 12, 1995 (8 wolves) and January 20, 1995 (6 wolves). They were released into three acclimation pens—Crystal Creek, Rose Creek and Soda Butte Creek in the Lamar Valley in Northeast East Yellowstone National Park. In March 1995, the pens were opened and between March 21 and March 31, 1995 all 14 wolves were loose in Yellowstone.[19]

Seventeen (17) additional wolves captured in Canada arrived in Yellowstone in January 1996 and were released into the park in April 1996 from the Chief Joseph, Lone Star, Druid Peak and Nez Perce pens. These were the last wolves released into the park as officials believed that the natural reproduction and survival were sufficient to obviate additional releases.[19][20]

Annual wolf status since reintroduction 

Yellowstone wolf pack territories in 2011

Wolf population declines, when they occur, result from "intraspecific strife," food stress, mange, canine distemper, legal hunting of wolves in areas outside the park (for sport or for livestock protection) and in one case in 2009, lethal removal by park officials of a human-habituated wolf.[22]

*1995-99 Data reflects status of the wolf in the Greater Yellowstone Ecosystem. Since 2000 monitoring has focused on packs operating within park boundaries. Wolves continue to spread to surrounding areas, and the last official report by the park for the Greater Yellowstone Area counted 272 wolves in 2002.

Annual Status of Wolves in Yellowstone (As of December)[23]
YearTotal Number of PacksTotal Number of WolvesNumber of Pups Surviving
1995* 3 21 9
1996* 9 51 14
1997* 9 86 49
1998* 11 112 36
1999* 11 118 38
2000 8 119 55-60
2001 10 132 43
2002 14 148 58
2003 13–14 174 59
2004 16 171 59
2005[24] 13 118 22
2006 13 136 60
2007 11 171 64
2008 12 124 22
2009[22] 14 96 23
2010[25] 11 97 38
2011[26] 10 98 34
2012[27] 10 83 20
2013[28] 10 95 41

Ecological impacts after re-introduction

Scientists have been researching and studying the impacts on the Yellowstone ecosystem since re-introduction in 1995.

As the wolf population in the park has grown, the elk population, their favored prey, has declined. Prior to reintroduction, the EIS predicted that wolves would kill an average 12 elk per wolf annually. This estimate proved too low as wolves are now killing an average of 22 elk per wolf annually.[29] This decline in elk has resulted in changes in flora, most specifically willows, cottonwoods and aspens along the fringes of heavily timbered areas. Although wolf kills are directly attributable to declines in elk numbers, some research has shown that elk behavior has been significantly altered by wolf predation. The constant presence of wolves have pushed elk into less favorable habitats, raised their stress level, lowered their nutrition and their overall birth rate.[30]

The wolves became significant predators of coyotes after their reintroduction. Since then, in 1995 and 1996, the local coyote population went through a dramatic restructuring. Until the wolves returned, Yellowstone National Park had one of the densest and most stable coyote populations in America due to a lack of human impacts. Two years after the wolf reintroductions, the pre-wolf population of coyotes had been reduced to 50% through both competitive exclusion and intraguild predation. Coyote numbers were 39% lower in the areas of Yellowstone where wolves were reintroduced. In one study, about 16% of radio-collared coyotes were preyed upon by wolves. Yellowstone coyotes have had to shift their territories as a result, moving from open meadows to steep terrain. Carcasses in the open no longer attract coyotes; when a coyote is chased on flat terrain, it is often killed. They feel more secure on steep terrain where they will often lead a pursuing wolf downhill. As the wolf comes after it, the coyote will turn around and run uphill. Wolves, being heavier, cannot stop and the coyote gains a large lead. Though physical confrontations between the two species are usually dominated by the larger wolves, coyotes have been known to attack wolves if they outnumber them. Both species will kill each other's pups given the opportunity.[31][32]

Coyotes, in their turn, naturally suppress foxes, so the diminished coyote population has led to a rise in foxes, and "That in turn shifts the odds of survival for coyote prey such as hares and young deer, as well as for the small rodents and ground-nesting birds the foxes stalk. These changes affect how often certain roots, buds, seeds and insects get eaten, which can alter the balance of local plant communities, and so on down the food chain all the way to fungi and microbes." [33]

The presence of wolves has also coincided with a dramatic rise in the park's beaver population; where there was just one beaver colony in Yellowstone in 2001, there were nine beaver colonies in the park by 2011. The presence of wolves seems to have encouraged elk to browse more widely, diminishing their pressure on stands of willow, a plant that beavers need to survive the winter.[34] The renewed presence of beavers in the ecosystem has substantial effects on the local watershed because the existence of beaver dams "even[s] out the seasonal pulses of runoff; store[s] water for recharging the water table; and provide[s] cold, shaded water for fish."[35] Beaver dams also counter erosion and create "new pond and marsh habitats for moose, otters, mink, wading birds, waterfowl, fish, amphibians and more."[33]

Wolf kills are scavenged by and thus feed a wide array of animals, including, but not limited to, ravens, wolverines, bald eagles, golden eagles, grizzly bears, black bears, jays, magpies, martens and coyotes.[33]

Meanwhile, wolf packs often claim kills made by cougars, which has driven that species back out of valley hunting grounds to their more traditional mountainside territory.[33]

The top-down effect of the reintroduction of an apex predator like the wolf on other flora and fauna in an ecosystem is an example of a trophic cascade.

2009 removal from Endangered Species List 

Wolf, Lamar Valley, 2011

Because gray wolf populations in Montana, Wyoming and Idaho had recovered sufficiently to meet the goals of the Wolf Recovery Plan, on May 4, 2008 the U.S. Fish and Wildlife Service changed the status of the gray wolf population known as the Northern Rocky Mountains Distinct Population Segment from Endangered to Experimental Population-Non Essential.[14]

The wolves in Yellowstone and the Greater Yellowstone Ecosystem fall within this population. In response to the change in status, state wildlife authorities in Idaho and Montana enacted quota-based hunting seasons on wolves as part of their approved state Wolf Management Plans. Environmental groups objected to the delisting and the hunting seasons, but despite legal attempts to stop them (Defenders of Wildlife et al v Ken Salazar et al), the wolf hunts, which commenced in Montana in September 2009 were allowed to proceed. A number of noted wildlife biologists that had been instrumental in the restoration of wolves—David Mech,[36] Douglas Smith,[37] and Mark Hebblewhite [38] supported the state wildlife management plans and the delisting because they believed the wolf populations were now at sustainable levels.

Although wolves within the park boundaries were still fully protected, wolves that ventured outside the boundaries of the park into Idaho or Montana could now be legally hunted. During these hunts, Montana hunters legally killed a number of wolves in the Absaroka-Beartooth Wilderness known to frequent the northeast corner of the park.

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