Wolves Make Mark on Yellowstone

  • The wolves in Kinna Ohman's report as seen through a spotting scope. Wolves have helped strengthen several species of plants and animals in Yellowstone National Park. (Photo by Marlene Foard)

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:

Transcript

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…”


(Sound of wolves howling)


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.


(Sound of creek)


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:


(Sound of footsteps)


“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.


For the Environment Report, I’m Kinna Ohman.

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