It started when park managers began the process of wolf extermination due to their destruction of domestic livestock within Yellowstone National Park. This self-centered decision led to a cascade of change in the food web which drove entire animal species toward endangerment. Only after the extinction of gray wolves within the region nearly 100 years ago did people realize the importance of this keystone species in moderating the equilibrium of the ecosystem.
The chain of events began with the 1800s westward expansion in the United States which destroyed many wildlife species, such as elk and deer, essential to a wolf’s diet. In turn, the wolves started to prey upon the settlers’ domestic stock resulting in the widespread extermination of wolves from areas such as Yellowstone Park. Between 1914 and 1926, around 136 wolves were killed — and by the mid-1900s, they were nearly eliminated from all 48 states within the U.S.
With the wolves gone, the elk began overpopulating the land, which led to the heavy grazing of various plant and tree species. Due to the reduction of dogwood and sarsaparilla berries, grizzly bear numbers declined as they were stripped of food, making it more difficult to gain body fat in preparation for hibernation. At present, the number of grizzly bears is yet to bounce back — as they occupy less than 2% of their former quantity in the lower 48 states.
In addition, the elks’ heavy grazing also served as a detriment to smaller animals and their ability to find adequate shelter. For example, the beavers struggled to build secure dams with the lack of twigs and bark while the number of mice and rabbits dwindled as it became increasingly difficult to find shelter away from predators.
Alongside the decline of numerous species, the heavy grazing significantly altered the topographical characteristics of the park by eroding the riverbanks. In turn, the water became clouded with soil, which led to heightened fish mortality — further trickling down to impact the lives of other animals that rely on fish for sustenance.
“Only after the extinction of gray wolves within the region nearly 100 years ago, did people realize the importance of this keystone species in moderating the equilibrium of the ecosystem.”
In response to these chain reactions, 41 gray wolves were reintroduced to Yellowstone National Park in 1995. Before this event, the main source of mortality for elks was deep snowdrifts. Now, the wolves were far more effective in preventing the overpopulation of elk and subsequent overgrazing.
With time, the elk numbers have greatly declined from around 17,000 in 1995 to 4,000 today. This has resulted in the return of scavengers, such as coyotes and eagles, with a more equitable distribution of elk carcasses available to feed on. In addition, the number of grizzly bears and smaller animals like songbirds has also increased due to the multitude of berries and shrubbery now available. The reduction in heavy grazing by elk has given various trees a chance to regrow, enabling stronger root structures that further support the riverbanks from erosion.
Although there is still a long way toward complete recovery, the Endangered Species Act (ESA) was passed in 1973, which requires the Federal government to aid in the protection of endangered and threatened species such as the grey wolf. In 1982, Congress added a section to the ESA that allowed the establishment of experimental populations — endangered species that are released into the wild and geographically separated from existing populations to encourage them to reproduce.
Another action taken to ensure the wolves’ safety is the act of capturing a small number of wolves and fitting them with radio tracking and GPS devices. This enables park researchers to gather data on specific wolves, monitor their whereabouts, and observe their interactions with other wildlife in the park.
As of January 2024, there are at least 124 wolves in Yellowstone National Park — a remarkable feat as the population continues to trend upward.
