The reintroduction of wolves into Yellowstone National Park led to a domino effect that vastly improved the park's ecosystem and biodiversity.
In the 1920s, wolves began disappearing from Yellowstone. Residents around the park had considered the wolves to be dangerous to people and livestock, so they hunted the animals down to the last wolf. By 1926, Yellowstone was wolf-free.
Back then, people didn't think much of the ecological role of wolves. They were just predators, and people thought that the wolves were hindering the ecosystem from flourishing.
Little did they know how important the wolves actually were.
The wolves' main prey were elk. When the wolves disappeared, the elk had a chance to flourish. And flourish they did. The elk population doubled in size in the absence of their predators. While this is great for the elk herds, it's not as great for the park's ecosystem and biodiversity.
Elk are grazers and browsers. This means that they feed on grass and other low-lying vegetation as well as on high-growing plants like shrubs and trees. When the elk population doubled, it put pressure on the vegetation in Yellowstone National Park. The plants weren't able to keep up with the appetite of the elk, each of whom can consume nine kilograms of food per day. Without the fear of wolves, the elk were able to eat to their heart's content.
Smaller animals like mice and rabbits suffered from the lack of vegetation. Without any grass or shrubbery to hide in, these smaller animals were more visible to their predators. Thus, the populations of these animals plummeted.
The elk gave even larger animals like bears a hard time. Bears need to feed on berries to build up fat before they go down for their long hibernation period. The elk, however, weren't leaving many berries for the bears to eat.
Birds, bees, and hummingbirds also got the short end of the stick. There weren't enough flowers for bees and hummingbirds to feed on because there were too many elk to contend with. Birds also had fewer trees in which to build their nests.
Even the banks of the Yellowstone river weren't safe. When the wolves were around, elk didn't spend too much time hanging out by the river to drink for fear of a wolf ambush. When the wolves disappeared, though, the elk came down to the banks in droves. The hooves of all these elk led to the erosion of the riverbanks, which then clouded the river's waters.
Thus, fish in the river lived in murky waters. Without clear waters and enough trees, beavers ceased building dams in the river. Beaver dams help control flooding and provide habitats that help nurture biodiversity.
All these things happened due to the disappearance of an apex predator that was thought to do more harm than good.
This is the first of a two-part series on the role of the gray wolf as a keystone species in Yellowstone National Park. To see what happened when scientists reintroduced wolves into the park's ecosystem, stay tuned for Part Two.
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