On a quiet hike in Yellowstone National Park, some lucky visitors might get to hear an amazing sound: the howl of a gray wolf.
They might even get to spot one of these beautiful animals darting across the landscape. In fact, today, the chances of seeing a wolf in some parts of this park — such as Lamar Valley — are so good that some people come just to wolf-watch.
When Yellowstone lost its wolves, it caused some big problems for the whole ecosystem.
Wolves are apex predators, which means they are at the top of the food web. When wolves were eliminated, it caused what scientists call a top-down trophic cascade. In other words, the whole ecosystem became unbalanced.
“Most ecosystems are best when they’re balanced,” Doug Smith, project leader for the Wolf Restoration Project in Yellowstone, said in a National Park Service Q&A. “Having a lot of different kinds of things at moderate numbers is better than having a lot of any one thing.”
Without wolves, there was a lot of one thing: elk. And biodiversity across the entire park declined as a result.
This hurt plants and other animal species. Willow and aspen trees started dying off — and that hurt the species that relied on these trees for their survival, such as the birds that use them as nesting grounds and the beavers that use the wood to build dams and survive the winter.
The numbers of rabbits and mice species fell, too, because of all the overgrazing. They simply had fewer places to hide from predators.
Everything started to change after scientists reintroduced 41 wolves into Yellowstone National Park.
The wolves thrived in their new home.
The newly formed packs spread out and established their territories, and the large populations of elk and deer provided them with ample prey. And because they were inside the national park, the animals were protected from hunters. So their numbers grew.
Because they are carnivores, wolves often get a bad rap — but the Yellowstone story shows just how important they are to our planet.
The ecosystem in Yellowstone is complex and always changing, but recent history has shown scientists and ecologists how important wolves are to keeping the natural balance. It is true that wolves hunt large animals, but they are not just killers — they also help other species thrive.
We all know the story about the “the big bad wolf.” But today, Yellowstone National Park is helping us learn a different story about wolves, and this is one is a lot happier.