![]() 16 Other studies suggest that wolves can reduce coyote populations 17 and thereby increase survival of pronghorn fawns upon which coyotes prey. 1,8,10,11 Some studies also contend that willow and aspen recovery might change the flow of streams 13-15, a topic that has gained considerable media attention. 10-12 As in other parks, studies conclude that wolf predation can contribute to willow and aspen recovery, and overall habitat diversity, by reducing overbrowsing by elk, benefiting songbirds and beavers. 1,8,9 Wolves also can change the behavior of elk, causing them to move more and use habitat differently by seeking more cover. This has led some researchers to infer that wolves caused the decline. 4,6 Since the reintroduction of wolves in 1995, the elk herd in Yellowstone’s northern range has declined substantially. Elk represent about 90% of wolf diet in this area. Yellowstone National Park has been a focus of many studies on the ecological role of wolves. This is primarily because wolf numbers have fluctuated over time due to a variety of reasons, including prey abundance, weather, and disease. Wolves have had strong effects during some periods but weaker influence during others. 4 However, since wolves colonized Isle Royale around 1949, the effects of wolves have varied over the years. Wolf predation is an important influence on moose populations, indirectly impacting vegetation by altering moose browsing. 4 Wolves are the only predator and primary cause of death for moose, which represent 90% of wolf diet. On Isle Royale National Park in northwestern Lake Superior, a research project ongoing for over 60 years has documented a unique predator-prey relationship between wolves and moose. Wolf recovery in the late 1960s apparently reduced elk use and allowed aspen to regrow. 7 Scientists used historical records on wolf and elk numbers to suggest that elimination of wolves in the mid-1900’s led to increases in elk browsing and declines in aspen. 2005Īnother study took place in Jasper National Park. Simplified trophic cascade caused by wolves in Banff National Park. This in turn reduced habitat quality for songbirds and beavers. When researchers compared low and high wolf density, they found fewer wolves led to increased elk numbers and greater browsing on willows and aspen (Figure 1). 5-6 Farther from town, wolf density was higher. In Banff National Park, development and human activity around the town of Banff kept wolf density low. 3,4 Multiple scientific studies have suggested that wolves, as apex predators, can have substantial ecological effects. Most such studies have been conducted in national parks such as Yellowstone and Isle Royale in the U.S. In short, it’s a complicated story with no simple answers. What are the ecological effects of wolves? Their loss can have cascading effects that alter aquatic and terrestrial systems throughout the world. Large carnivores are particularly susceptible because of their naturally low numbers, wide ranges, and active predator control by people. 1 Apex predators such as large carnivores are some of the first animals to decline or disappear when they share landscapes with people. A growing number of studies globally have documented trophic cascades generated by apex predators. They can cause ecological effects that ripple through an ecosystem. Predators at the top of the food chain are known as apex predators. In areas with lower densities of wolves, ecological effects will be less evident. ![]() Ultimately, if restored to Colorado, wolves might generate noticeable ecological effects where they occur in high enough densities for long enough time. Predicting the ecological effects of wolves is complicated, with no simple answers.Additional factors such as drought, harsh winters, other predators, and human hunting may have also helped reduce the Yellowstone elk herd and transform the ecosystem. Wolves are likely not solely responsible for the changes in the Yellowstone ecosystem.In places like Yellowstone National Park, wolves have likely contributed to willow and aspen recovery and overall habitat diversity by reducing overbrowsing by elk. Wolves can generate trophic cascades – ecological effects that ripple through an ecosystem.By the Center for Human-Carnivore Coexistence (5/20) Key Points….
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