The Gray Wolf once roamed freely throughout more than two-thirds of the United States. However, they were extirpated (locally extinct) from most areas of the U.S. when settlers from Europe came to the new world. Throughout history wolves have been villainized, but in recent years many states have debated the reintroduction of the Gray Wolf. As areas of the U.S. are reintroducing the species we are seeing the dramatic impact that this canine can have on an ecosystem. The Gray Wolf is known as a keystone species, a species that has such a disproportionate effect on an ecosystem, such that if it were removed, the ecosystem would change drastically. Colorado passed a ballot measure to reintroduce wolves to the state last November, and areas throughout the western United States have movements for reintroduction.
What makes the wolf a keystone species, and what kind of impact does it have on their ecosystem? To answer that question we first have to begin with why the wolf was extirpated in the first place. Human relationships with wolves have been long and complicated, starting with when we first arrived from Europe. As settlers moved out west, ranches replaced a significant amount of elk and deer habitat. Wherever their main food source was mostly eliminated, wolves turned to livestock. This quickly made wolves the new enemy of the settlers. When the wolves gained a new predator and had a strain put on their food source, they became extirpated in most areas of the United States.
Some studies have given us an idea of what happens when the wolf reenters an environment it once roamed, like the reintroduction of wolves in Yellowstone Park in 1995. When the wolf came back to Yellowstone the deer populations decreased, an interested chain reaction also started to happen. The behavior of the deer changed. They stopped grazing out in the open and were more careful about where they went and when they came out. Once that happened, bare valleys became forests. When the vegetation returned, the bird population grew. Beavers, another keystone species, returned because riparian plants were now growing in abundance. The wolves also competed with coyotes, which meant that more rabbits and mice survived, which led to more hawks in the park. Bears, ravens, and eagles began to feed on carrion, the decaying flesh of dead animals, that wolves would leave and all of their populations increased. When riparian vegetation improved, it stabilized the river banks and less erosion occurred. Not only did the reintroduction of the wolves change the ecosystem of
Yellowstone, but it changed the geography of the land.
We are still learning about the effects of the wolf reintroduction in Yellowstone and other areas of the West decades later. Colorado and the Southern Rockies, however, have many differences so we can’t predict all of the ways that our ecosystems will change when wolves are reintroduced to the state. We know that wolves are a keystone species, this much is apparent. It is up to citizens to learn from the plethora of wolf biology studies to help inform the process of reintroduction over the next few years.
Chase McNair was a 2020 Naturalist at Walking Mountains Science Center and loves spending her time outdoors and learning about the relationships between animals and people. You can expect more wolf articles and presentations to come as Coloradans prepare for reintroduction!