The reintroduction of wolves into Yellowstone National Park
The Grey Wolf (Canis lupus)
Hundreds of years ago, the Grey Wolf (Canis lupus) used to inhabit most parts of the
world, making it one of the most widely distributed mammals in the world. Today, the
species has sadly become extinct in most of Western Europe and the United States,
mostly because of the destruction of its habitat and a widespread view that the wolf is
a threat to people and livestock. In Europe, the wolf was hunted from the Middle
Ages on. In the United States, its population was reduced to only 20% of its original
size in less than 50 years. Human attacks by wolves are extremely rare, but humans
have always feared the wolf, which shows in many myths and folklore stories.
The eradication of wolves in Yellowstone Park
Yellowstone, the United States’ first National Park, was established in 1872 and
measures ca. 9000 km², making it the largest remaining continuous area of
undeveloped land in the United States. In order to make it a more safe and enjoyable
place for visitors, predator control was introduced. This means that from the early
1900s on, predators such as wolves, bears, coyotes and mountain lions were
systematically hunted and trapped. In 1926, the last Grey Wolf was killed in
Yellowstone.
The effects on Yellowstone through the loss of the wolves
The eradication of the Grey Wolves from Yellowstone had a huge
ecological impact on the park’s environment, especially on its food
web. Since the wolf was the main predator of the elk herds living in
Yellowstone, the elk population greatly increased. Since elks love to
eat willow saplings, there was a reduction in the amount of willow
trees, which was a problem for several reasons. On the one hand, the
reduction of willows led to an increase in the stem diameter of the
willows, many of which where then too thick for the beavers to use for
their dams. Because the willows help stabilize the riverbanks, less
willows led to the widening of many rivers. Both the river widening
and the missing beaver dams led to a change in the river flow, which
had a negative impact on fish populations. Fewer willow trees also
impacted bird populations, since these not only feed on willow seeds
but also use them as habitats.
wolf eradication
increase in elk
herds
reduction of
willows
Words you might not know:
distributed:
continuous:
predator control:
spread
unbroken, uninterrupted
Bekämpfung von Raubtieren
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change in river
flow
Because of the wolves’ huge impact on many other species of the Yellowstone
ecosystem, ecologists consider them a keystone species. Even though keystone
species don’t appear in huge numbers, they have a large effect on their surrounding
environment. Therefore, its removal can cause a dramatic shift for an ecosystem and
its other species. In the case of the Yellowstone Wolves, people realized the wolves’
importance for the park’s ecosystem and decided to take measures.
The reintroduction of wolves into Yellowstone
Because of the devastating effects
the removal of the wolf had on the
park’s
ecosystem,
ecologists
suggested its reintroduction. In
1995, 14 Canadian wolves were
brought to Yellowstone, and a
year later, another 17 were
reintroduced. Before the wolves
were let free, they were held in
large enclosed pens, which is
called soft release technique,
because the animals had time to
Fig. 1: Grey Wolf in Yellowstone (www. Riccardoschweizer.ch)
acclimatize
to
their
new
environment. Human contact was kept as little as possible, and the wolves were fed
bison, moose, elk or deer that had died in the park. In order to keep track of their
movements, the wolves were fitted with radio collars. The individuals that were
released into the park produced offspring, and in 2004, the wolf population inside the
park consisted of 171 individuals, the population outside of the park 324.
Impacts of the reintroduction
It will take many years for ecologists and biologists to collect enough data in order to
make specific statements on the success of the reintroduction of the wolves. As of
today, it seems that the Yellowstone ecosystem is recovering. Visitors of the park
now have the opportunity to find every species of large carnivores that inhabited the
park when it was established in 1872. That includes Grey Wolf, Coyote, Grizzly Bear,
Black Bear, and Cougar. As of October 2004, more than 130,000 visitors reported
having seen a wolf in its natural habitat. According to the Yellowstone National Park
Website, the wolves help “regulate prey populations, control disease, and provide
food to a wide variety of other animals such as ravens, magpies, and grizzly bears ...
The wolf’s presence appears to be leading to greater biodiversity and stability”.
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Conflicts
When the wolves were reintroduced, there was a lot of critic from concerned people.
Many ranchers were afraid that the they would prey on cattle and domestic animals.
Indeed, the wolves also roam outside the boundaries of the park, and between 1995
and 2004, 219 cattle and 516 sheep in the greater Yellowstone area were killed. Due
to this, many ranchers are fighting for the right to hunt and kill wolves that attack
livestock on their property. In order to prevent this, a nonprofit organization,
Defenders of Wildlife, reimburse ranchers who can prove that a wolf has preyed on
their livestock. Ranchers also state that there has been a reduction in their cattle
weight, because the cattle can only graze in less areas. Others fear the migration of
the wolves into human habitat, which they think could cause a threat to pets and
humans, and the elk hunting business in Gardinger in Wyoming, has declined
significantly due to the smaller elk herds.
Significance
“The reintroduction of the gray wolves ranks symbolically among the most important
acts of wildlife conservation in the 20th century.”
The conservation efforts that have been made to preserve the Grey Wolf not only in
Yellowstone, but in many other parts of the world, has shown that there is indeed a
change of thinking occurring today. More people are realizing that it is not our right to
control and tame wilderness, but that it is our duty to preserve it. Hopefully we will
continue to learn from our past mistakes and try to give future generations the
opportunity to enjoy the earth’s biodiversity as we do today.
Tasks:
1. Mark all of the vocabulary that you don’t know. If you don’t understand their
meaning in context, look them up.
2. The eradication of wolves from Yellowstone had a huge impact on its
ecosystem. Create a diagram that shows all impacts of the missing wolves.
3. Considering the conflicts that have come up, do you think the reintroduction of
the wolves was a good or bad idea? Write a short text (5-8 sentences) by
using arguments mentioned in the text. You may of course add your own
arguments.
4. In the last few years, some wolves have migrated back to Germany from
Poland and the Czech Republic. Try to find out how many there are and where
they live now. Hint: you might find useful material on
http://www.naturdetektive.de.
http://biologiebilingual.jimdo.com/teaching-material/conservation-biology/case-studies/