Grey Wolf Population in Yellowstone

Introduction

When Yellowstone was first appointed as a national park in 1872, there was no legal protection for any of the wildlife (Dockrill, 2018). Over time, government predator control programs significantly contributed to the mass culling and subsequent extirpation of the grey wolves in Yellowstone by 1926 (Wikipedia, 2019). The eradication of this apex predator had unintended consequences on the ecosystem, causing a trophic cascade (Dockrill, 2018). The absence of the grey wolf caused a large relief of predatory pressure on the elk population, causing them to thrive (Farquhar, 2019). This surge in numbers resulted in significant overgrazing of aspen, cottonwood, and willows, which are vital for providing shelter, food, and dam-building resources for beavers who migrated to the northern range of the park. Consequently, these dams collapsed, turning swamps into flowing streams. There was major stream erosion and loss of mature aspen, cottonwood, and willow, affecting an array of animal and plant species. In the wolf's absence, the coyote became an apex predator, diminishing populations of red foxes, rodents, pronghorn antelope, and birds. Local scavenger species, including grizzly bears, eagles, and ravens, also suffered greatly with no wolf kills to rely on and feed from. After the wolf was reintroduced into the ecosystem in the northern range, coyote numbers drastically declined by 50%, allowing fox, rodent, and antelope populations to flourish again. The elk population began to decline, and the single beaver colony increased to 12. Insects, birds, amphibians, and fish began to thrive again, as did the vegetation. Scavenger populations benefited too, feeding off the wolves' leftovers. The wolves caused the rivers to meander, erode, and collapse less due to the regenerating stability of the vegetation. Many more pools were formed. Elk also changed their behaviors, avoiding valleys and gorges, places where they could be trapped by predators, allowing these areas to regenerate significantly (Earthjustice, 2019).

Historical Context and Impact of Grey Wolf Extirpation

When first established, there were no protective laws for animals in the park, and people were essentially free to hunt all wildlife. The Secretary of the Interior declared a policy forbidding hunting of the majority of the park’s wildlife in 1883; however, the policy did not apply to wolves, bears, coyotes, and other predators. Poisoning was a form of predator control used in the park during the late 1800s and early 1900s (Wikipedia, 2019). Poisoning is a highly unethical and inhumane method of predator control, involving unnecessary pain and cruelty. The Yellowstone National Park Act of 1872 newly stated that the Secretary of the Interior would protect against the vicious destruction of all wildlife within the park; however, the wolves’ habitual killings of prey were considered “vicious destruction,” causing at least 136 wolves to be killed in the park from 1914 to 1926. By the mid-1900s, wolves had been almost entirely eliminated across North America (National Park Service, n.d.). The government's public vocalization and actions against wolves influenced the public’s view of the wolves, leading them to believe that their presence was a nuisance and supporting the idea that the park would thrive without them (Wikipedia, 2019).

Ecological Consequences of Wolf Extirpation

Predators maintain balance in an ecosystem through populations and food webs; therefore, the extirpation of grey wolves in Yellowstone sent the ecosystem into a trophic cascade. The removal of wolves had indirect influences throughout the ecosystem, altering the densities of lower trophic herbivores and thereby affecting the growth of primary producers (Living with Wolves, 2019). The populations of herbivores exploded, consequently causing severe overgrazing and suffering waterways, radically reducing many species' key food sources and habitats. Many species that relied on microhabitats, including songbirds, amphibians, reptiles, and insects, effectively vanished. Unforeseen by biologists, the structure of the ecosystem changed drastically. This extirpation allowed biologists to witness one of the few and most recognized examples of top-down trophic cascade. Only then did biologists fully comprehend the complexity of the ecosystem, initiating widespread efforts and research into the reintroduction of the wolves (Duffey, 2019).

Reintroduction and Recovery Efforts

As a result of federal and state predator controls, grey wolves were listed under the Endangered Species Act (ESA) in 1973. Collaboratively, the National Park Service, Fish and Wildlife Service, state wildlife agencies, and environmental groups developed a restoration plan for the wolf (Wikipedia, 2019). In January 1995, 14 wolves from Alberta, Canada were captured and brought to Yellowstone to be released in March after a trial period. An additional 17 wolves were also released in April 1996. As of December 2014, the wolf population stood at 104 in 11 packs (Dockrill, 2018). While the reinstated wolves of Yellowstone were protected within the park’s boundaries, a wolf hunting and trapping season was used to take place in areas adjacent to the park to maintain numbers. However, after only one season, in 2014, a US Federal Court ordered a stop to wolf hunting in parks in surrounding states after the tagging limit of 400 was exceeded (Wikipedia, 2019). All of the reintroduced wolves were also radio-collared before their release, allowing them to be monitored. The collected information has allowed the Wolf Project to study survival, reproduction, dispersal and distribution, sociality and genetics, disease, and predation on ungulates (Yellowstone Wolf, n.d.).

Economic and Societal Benefits

The reintroduction of wolves had both economic and societal benefits for the park. A survey conducted after reinstatement showed a 3.5-4% increase in tourism, equating to approximately 120,000 visitors and a subsequent increase in income and popularity. The strict hunting ban also ensures that these numbers continue to incline (My Yellowstone Park, 2011). Organizations such as Yellowstone Forever monitor the wolves through their collars, ensuring they remain healthy and observing their interactions throughout the ecosystem (Yellowstone, 2019). These efforts helped secure the grey wolf population, allowing each trophic level to remain stable, resulting in the removal of the endangered status in 2008 to Experimental Population-Non-Essential.

References

• Dockrill, P. (2018). How Wolves Reshaped Yellowstone National Park. ScienceAlert.
• Wikipedia. (2019). Grey Wolf Reintroduction. Retrieved from https://en.wikipedia.org/wiki/Grey_wolf_reintroduction
• Farquhar, B. (2019). The Impact of Wolves in Yellowstone. National Geographic.
• Earthjustice. (2019). How Wolves Change Rivers.
• National Park Service. (n.d.). The Role of Predators in Yellowstone.
• Living with Wolves. (2019). The Importance of Wolves.
• Duffey, M. (2019). The Ecological Impact of Wolves. Ecological Society of America.
• My Yellowstone Park. (2011). Economic Impact of Wolves in Yellowstone.
• Yellowstone Wolf. (n.d.). The Wolf Project.
• Yellowstone. (2019). Monitoring the Wolves.