By Kinna Ohman
SCIENTISTS are surprised by the changes one animal can make in America’s first national park. Since the wolf returned to Yellowstone, the predator’s had wide-ranging and unexpected effects on the ecosystem of the park.
As Kinna Ohman reports, top predators such as wolves might be more necessary than previously realized:Yellowstone National Park holds many wonders, but few things capture a visitor’s imagination like the wolf:
“Whoa, I can see their eyes.”
Marlene Foard lets me peek through her scope and see members of the Slough Creek wolf pack tearing into a recent kill. As we watch, we hear another group of wolves howling in the distance:
“Did you hear ’em? Yeah, did you hear that? Oh my God…”
Visitors are not the only ones fascinated by the wolves. Lately, scientists have been caught up in the excitement too. Not just by the wolves, but how the wolves are changing Yellowstone.
It’s a cold yet sunny day in the park. I’ve met up with Doug Smith, the project leader of the park’s wolf recovery program. But we’re not going to look for wolves today. We’re about to see how wolves are changing the landscape:
“This is Blacktail Deer Creek that we’re walking up on. And it’s surrounded by willows. And these willows about ten years ago were not growing as luxuriantly as they are right now.”
This new willow growth happened after the wolves’ reintroduction to Yellowstone, and many scientists are making a connection. Willow can be a food for elk especially in the winter, but since the wolves have returned, elk would rather be on hillsides and open areas where they can see wolves coming. And once they leave the river valleys behind, plants like the willow are recovering.
The willow’s recovery is important because it helps other wildlife. Beaver eat willow and use it for building dams. And ponds created by beavers are great habitat for endangered birds, like the warbler. Doug Smith says the fact this could be caused by wolves caught everyone by surprise:
“Nobody thought of this. I was around at the beginning. There were many studies done looking at what the impacts of wolves would be. And I can’t remember reading about this at all.”
And it goes beyond the willow. Bill Ripple is a professor of Ecology at Oregon State University. He came to Yellowstone in 1997 to study why aspen trees were declining. Ripple wasn’t thinking wolves, but one day, when studying tree ring data, he saw the aspens’ problems began just when the last wolves were killed off in Yellowstone. He was equally surprised:
“I didn’t see anything in the record. It wasn’t on my radar to see how wolves may be affecting aspen trees. That was not even considered at all. And all of a sudden, it appears that this one animal can have this profound effect on the entire ecosystem.”
And this got Ripple thinking about the top predators a little differently. He says these effects might even extend to other animals:
“I think that this effect of predators would probably go well beyond just cougars or wolves. You know everything from black bears to grizzly bears to lynx to wolverines. They may all play important roles that we don’t even know about at this point.”
Not everyone thinks predators are needed for ecosystems to thrive. There are hunters who consider wolves unnecessary and even competition for animals such as deer and elk, but Doug Smith says it’s important to realize the contribution of wolves goes beyond what hunters can do. Willow and aspen re-growth depends on wolves changing elk behavior.
And this has to happen year round:
“Human hunters, well known this fact, and I’m a hunter and I know this, prey behavior changes during the hunting season, and before and after they go back to doing what they want. Having a carnivore on the landscape changes prey behavior year round. A totally different presence than human hunting.”
But there’s a caveat. Smith says there has to be a certain number of wolves on the landscape for these changes to occur. And the number might be more than humans are willing to tolerate:
“You know, just having wolves on the landscape does not do it. And that’s a very, very important point because some people are using wolves to argue that we’re going to get this ecosystem restoration, this ecosystem recovery. But they need to be at a certain minimum density. And that might be in some places at densities that are too high for humans to socially tolerate.”
So, ultimately, ecological recovery could depend on humans, not the wolves. Human tolerance needs to be high enough to allow top predators like the wolf to return to ecosystems, otherwise, full recovery might never happen.–Environment Report