Tuesday, May 21, 2024
HomeConsider ThisMore Wolves = More Trees and More Pronghorn Antelope

More Wolves = More Trees and More Pronghorn Antelope

When wolves were reintroduced in Yellowstone National Park in 1995, no one was anticipating that their arrival would improve tree growth. But it did. No one expected that more wolves would mean more pronghorn antelope either. But it turns out that thanks to wolf reintroduction, more pronghorn fawns began surviving.

How Did Wolves Do All This?

Druid wolf pack chasing a bull elk in Yellowstone. Photo by Doug Smith, December 2007

Yellowstone National Park had an elk problem in 1995 when the wolves arrived on the scene. There were too many of them, and the park was beginning to suffer from overgrazing. Cottonwoods, willows,aspen and other woody species were disappearing thanks to about 15,000 elk chowing down on them. The problems was especially problematic along streams and rivers, causing water temperatures to rise and beaver and riparian songbirds to disappear along with the trees and brush they relied on for survival.

The wolves did two things. First, they ate some elk and slowly the population began to decline to a level the park could support. They also changed the behavior of the remaining elk who had to spend time watching out for predators, giving them less time to graze off tasty aspen shoots.

As a result, trees and shrubs began recovering along streams. Habitat improved for beaver and fish. Bears had more food, and hundreds of species of birds, mammals, fish and reptiles began to return to their niche in Yellowstone’s ecosystem. By 2006, some aspen trees had grown tall enough they were no longer susceptible to browsing by elk. Cottonwood and willow were also beginning to return in places so that songbirds, like the common yellowthroat, warbling vireo and song sparrow could once again be found in the Park. And thanks to the work of beavers building dams, waterfowl found new homes too.

Mature aspen surrounded by younger trees that have been able to grow thanks to less browsing by elk. Photo courtesy of Oregon State University.

Wolves also changed coyote populations and behavior. Some coyotes were killed by wolves and others shifted to safer areas without wolves. Fewer coyotes meant increases in populations of small mammals, a good thing for the red foxes, ravens and bald eagles that rely on them for food and pronghorn antelope numbers went up too.

While we might have expected wolves to eat the fawns, that isn’t what seems to happen. According to researcher Dr. Kim Berger, “wolves are so much bigger than coyotes that it doesn’t make sense for them to waste time searching for pronghorn fawns. It would be like trying to feed an entire family on a single Big Mac.” Researchers found that where coyotes had been dense, only 10% of fawns survived. But where wolves were present, survival rates went up to 34% and the Yellowstone herd has doubled from a low of 200 in 1995 to about 450 today.

What we’ve learned is that the relationship between predators and prey can be very complex and our efforts to manipulate ecosystems can have unexpected consequences. While wolves may not be a welcome sight for many ranching operations in the west, perhaps understanding their behavior and their place in the ecosystem will help us come up with better ways to protect stock. If you’ve found something that is particularly helpful, please share it with your fellow On Pasture readers below.

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Kathy Voth
Kathy Vothhttps://onpasture.com
I am the founder, editor and publisher of On Pasture, now retired. My career spanned 40 years of finding creative solutions to problems, and sharing ideas with people that encouraged them to work together and try new things. From figuring out how to teach livestock to eat weeds, to teaching range management to high schoolers, outdoor ed graduation camping trips with fifty 6th graders at a time, building firebreaks with a 130-goat herd, developing the signs and interpretation for the Storm King Fourteen Memorial trail, receiving the Conservation Service Award for my work building the 150-mile mountain bike trail from Grand Junction, Colorado to Moab, Utah...well, the list is long so I'll stop with, I've had a great time and I'm very grateful.


  1. Obviously a lot of emotion related to re-introduction of the top tier native predator. Part of me wonders what would have happened if private hunting permits were allowed to reduce elk and coyote populations. I also understand the benefit of having the wolves target the weak, old and sick animals. Seems fair that any animal who becomes a nuisance whether wolf or elk on private lands adjacent to the park should be able to be targeted and removed. I’ve also learned from multiple sheep and goat ranchers that if they can get their local predators “trained” to leave livestock alone then their territorial nature keeps rivals away and predation is zero or very close. I believe US Fish and Wildlife is working with the red wolf re-introduction to their native range in New Mexico to use lithium oxide to teach the predators to leave livestock alone setting carcass traps. Complex and Complicated problems require complex solutions.

  2. The wolves have only been there 22 years. That is not even a eye blink of time to judge the success or not of the introduction. Wolves off the bounds of the park should be subject to hunting, with a determined number of permits and kills.

  3. I’m not sure that the introduction of a non-native species is the answer. I hear and read far more negative effects from the introduced wolf population than I do positive. I think that misleading people to believe this is a reintroduction is wrong. I am a firm believer in Holistic management. There was not any consideration given to the local agricultural community when these wolves were introduced in Yellowstone. Now there population has grown and expanded it’s territory. Perhaps had the local ranching community been asked for input and to participate on an advisory committee a Holistic solution could have been found. Instead they have been made to feel that their livelyhood has no meaning and they have been cast aside. There are many ranchers that have successfully been implementing grazing practices that are wildlife friendly. Many conservation organizations have seen the positive impacts of grazing on wildlife habitat.

  4. When we named our farm Howling Wolf Farm nearly twenty years ago, it represented the hope of creating a healthy functioning ecosystem in the context of a farm. It’s a good reminder to me still; a goal and priority of our farming system is to work with and understand natural systems, not fight against them.

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