Throughout much of the 20th century, this is a sound you weren’t likely to hear in Yellowstone
National Park. In fact, you weren’t likely to hear it throughout much of the United States.
Wolves were almost completely eliminated from the lower 48 by the mid 1900s,
and were completely eliminated from Yellowstone in 1926.
Yellowstone was wolfless for the first time in more than 12,000 years.
But the seeds of this extermination were planted decades before.
As more and more settlers came west, they removed much of the wolves’ natural prey.
Naturally, the wolves responded by preying on the homesteaders’ livestock,
setting the scene for an ecological showdown the wolves would ultimately lose.
When wolf-human conflict began arising,
the government supported policies that included hunting, trapping, and poisoning wolves - all in
an effort to protect livestock. But it wasn’t just cows and ranchers benefitting from these policies.
The government considered both elk and deer to be “more desirable species” than wolves.
The National Park Service even used its own conservation mandate as a
justification for killing wolves. Under the Yellowstone National Park Act of 1872,
the Secretary of the Interior was tasked with protecting against “the wanton destruction of
the fish and game found within the park.” In their eyes, when wolves killed an elk or a deer,
they were “destroying” the very ecosystem the Park Service had sworn to protect.
It’s against this backdrop that the systematic removal of wolves from Yellowstone began.
Now, this may seem woefully misguided by today’s standards, but it’s important to remember that
the complexity of these ecosystems simply wasn’t understood like it is now. Park officials were
simply doing what they thought was best to protect the world’s first national park.
But, it also didn’t take long for biologists to figure out that something was wrong.
By the late 1920s, not even five years after the elimination of wolves from Yellowstone,
biologists began to notice that certain species of vegetation were going missing,
soils were eroding, and invasive grasses were taking hold.
Throughout the twentieth century, evidence would continue to present itself that Yellowstone needed
its wolves. And in 1973, an opportunity arose to bring back the park’s top predator: the Endangered
Species Act. Under the ESA, the Fish and Wildlife Service is required to recover endangered animals
where it is possible to do so. Yellowstone was a perfect candidate, and in 1975 preparations began
to bring the gray wolf back to Northwestern Wyoming. It would take 2 decades before those
preparations were complete, but in 1995 8 wolves roamed Yellowstone’s frozen tundra once again.
The reintroduction was, of course, contentious. The same fears that led
to the wolf’s extermination nearly a century ago were still present in 1995. Ranchers and
farmers worried that their very livelihoods were at stake. Despite little evidence that
wolf predation is a major source of livestock loss, these sentiments are still echoed today.
But ecologically, the wolf restoration was a resounding success.
Wolves triggered what ecologists call a trophic cascade. Now, I talked about trophic levels in
my last video about Isle Royale, so if you haven’t seen that yet, you can pause this
video and check that out. I’ll link to it down below. Basically though, a trophic cascade is
where a top level predator, in this case wolves, limits the number of its prey, in this case elk.
With elk numbers limited, organisms at the next trophic level then increase their numbers,
in this case willow, aspen, and cottonwood trees. Essentially, the wolves at the top of
the food chain were directly responsible for the return of these tree species in
Yellowstone - simply because the elk were no longer eating them. This is a trophic cascade.
And it doesn’t stop there. The return of wolves brought a whole host of ecological
benefits back to an ecosystem that so desperately needed them.
With the aspens, willows, and cottonwoods growing again,
songbirds returned to their canopies to nest and to raise their young.
The new streamside trees meant beavers could once again build dams.
Prior to wolf reintroduction, just 1 beaver colony called Yellowstone home. Now, there are 9.
Those beaver dams, in turn, provided valuable new habitat for fish,
salamanders, reptiles, muskrats, otters, and a whole host of other small animals.
With wolves back in the picture, there were now more elk carcasses for scavengers to,
well, scavenge. Prior to wolves, animals like bears, cougars, ravens, and eagles all had to
compete for the few carcasses leftover from winter if they wanted to feed. The increase in carcasses
meant plenty of food for all, and the numbers of each of those animals once again began to climb.
Wolves also meant a decline in the coyote population. When wolves were scarce,
coyotes preyed on rabbits, weasels, badgers, and even pronghorn.
The return of Yellowstone's top dog saw all of these populations increase.
Wolves, quite literally, transformed Yellowstone’s ecosystem.
An overgrazed and barren rangeland, overrun with elk, came back to life.
Yellowstone now teemed with a diversity and abundance of life not seen for nearly a century.
But, remarkably, the impact of the wolf...goes even further.
In the decades that followed the Yellowstone wolf reintroduction,
researchers began to observe something truly extraordinary: the elk were scared.
Wolves were not only killing and eating the elk, triggering an almighty trophic cascade
in the process, but their very presence was changing elk behavior. For decades,
with no real threat to their lives, elk browsed languidly in Yellowstone’s river valleys. They
were free to roam, graze, and eat their way through Yellowstone’s vital riparian vegetation.
But when the wolves returned, their very presence meant the elk had to be more vigilant,
more alert to their surroundings, always on the lookout for those pesky wolves.
And so, they browsed less, they didn’t stay in one place too long,
and crucially, they avoided the very streambanks where aspens and willows grew so well.
Simply by existing, wolves had changed the very nature of Yellowstone.
And all they did was do what came naturally to them. There was nothing special, nothing
extraordinary about these wolves. They were simply returned to an ecosystem that needed them,
that had adapted alongside them. In their absence,
that ecosystem had grown sick, but with their return had grown healthy again.
I’ve got one more predator story to share with you, so stay tuned next time as we finish out this
series. If you haven’t seen the first installment, you can find the link in the description below.
And as always, if you want to learn more about the world’s protected places,
don’t forget to like this video and subscribe to the channel.
It helps me bring more park stories to more people. Thank you so much for watching, goodbye.