Environmental Science 15th Edition by Scott Spoolman,Tyler Miller

Exercise 22

REINTRODUCING THE GRAY WOLF TO YELLOWSTONE NATIONAL PARK
Around 1800, at least 350,000 gray wolves (Figure 9.B) roamed over about three-quarters of America's lower 48 states, especially in the West. They survived mostly by preying on abundant bison, elk, caribou, and deer. However, between 1850 and 1900, most of them were shot, trapped, or poisoned by ranchers, hunters, and government employees, and they were driven to near extinction in the lower 48 states.
Ecologists recognize the important role that this keystone predator species once played. In the Yellowstone National Park region, the wolves culled herds of bison, elk, moose, and mule deer, and kept down coyote populations. By leaving some of their kills partially uneaten, they provided meat for scavengers such as ravens, bald eagles, ermines, grizzly bears, and foxes.
When the number of gray wolves declined, herds of plant-browsing elk, moose, and mule deer expanded and devastated the willow and aspen trees growing near streams and rivers. This led to increased soil erosion and to declining populations of other wildlife species such as beaver, which eat willow and aspen. This in turn affected species that depended on wetlands created by dam-building beavers.
When Congress passed the U.S. Endangered Species Act in 1973, only a few hundred gray wolves remained outside of Alaska, primarily in Minnesota and Michigan. In 1974, the gray wolf was listed as an endangered species in the lower 48 states.
In 1987, the U.S. Fish and Wildlife Service (USFWS) proposed reintroducing gray wolves into the Yellowstone National Park to try to help stabilize the ecosystem. The proposal brought angry protests from area ranchers who feared the wolves would leave the park and attack their cattle and sheep, and from hunters who feared the wolves would kill too many big-game animals. Mining and logging companies objected, fearing that the government shut would halt their operations on wolfpopulated federal lands.
In 1995 and 1996, federal wildlife officials caught gray wolves in Canada and northwest Montana and relocated 41 of them in Yellowstone National Park. Scientists estimate that the longterm carrying capacity of the park is 110 to 150 gray wolves. By 2007, the park had 171 wolves, but that number had dropped to 82 by the end of 2012, for various reasons having to do mostly with the supply of prey for the wolves. Such population fluctuations are natural, according to the National Park Service.
Wildlife ecologist Robert Crabtree and other scientists have been studying the effects of this reintroduction. They have put radio collars on most of the park's wolves to gather data and track their movements. They have also studied changes in vegetation and in the populations of various plant and animal species.
Studies indicate that the return of this keystone predator has contributed to a decline in populations of elk, the wolves' primary food source. The leftovers of elk killed by wolves have also been an important food source for scavengers such as bald eagles and ravens. The wolves' presence, with a projected decline in elk numbers, was supposed to promote the regrowth of young aspen trees that elk feed on and had depleted. However, a 2010 study led by U.S. Geological Survey scientist Matthew Kauffman indicated that the aspen were not recovering despite a 60% decline in elk numbers. Declining populations of elk were also supposed to allow for the return of willow trees along streams. Research indicates that willows have only partly recovered.
The wolves have cut in half the Yellowstone population of coyotes-the top predators in the absence of wolves. This has reduced coyote attacks on cattle from area ranches and has led to larger populations of small animals such as ground squirrels, mice, and gophers, which are hunted by coyotes, eagles, and hawks. Overall, this experiment has had some important ecological benefits for the Yellowstone ecosystem. However, some scientists hypothesize that the long-term absence of wolves led to a number of changes in plant and animal numbers and diversity that are difficult to reverse.
The wolf reintroduction has produced economic benefits for the region. One of the main attractions of the park for many visitors is the hope of spotting wolves chasing their prey across its vast meadows.
Between 1974 and 2012, the wolf population in the lower 48 states grew from around 100 to roughly 5,400 individuals. In 2013, the USFWS proposed removing the gray wolf from the U.S. endangered species list in the lower 48 states and turning over wolf protection responsibilities to state wildlife agencies. More than 750,000 Americans sent comments to the USFWS stating their opposition to this plan. Conservation groups plan to fight the proposal in court, arguing that it could lead to greatly increased killing of the ecologically important gray wolf.
Critical Thinking
Do you think gray wolves should remain on the U.S. endangered species list? Explain.

FIGURE 9.B After becoming almost extinct in much of the western United States, the gray wolf was listed and protected as an endangered species in 1974.