Wolves in Yellowstone Park A Story about Ecosystem Balance
Yellowstone: A National Park In 1872, Yellowstone (in the state of Wyoming) was declared the first national park in the United States.
Geologic Wonders Yellowstone is famous for its beautiful geologic features: hot springs, mountains, lakes, and forests.
The Beauty of Nature But people also came to Yellowstone park to enjoy the beautiful plants and peaceful animals, like elk.
Predators and Prey Wolves eat elk. Some people were upset that the beautiful elk were being eaten by the wolves.
Get Rid of the Wolves The U.S. government gave permission to hunters to kill the wolves. By 1926, all the wolves were gone.
Do We Need Wolves? The park officials thought they were helping. They didn t understand that wolves are important to the ecosystem.
What do you think happened? What do YOU think happened when the wolves were gone? Write one prediction on your answer sheet.
Cause / Effect Flow Chart Now, as you read the next section, fill in the cause & effect chart to show what happened to the Yellowstone ecosystem after the wolves were gone.
When the Wolves Were Gone
Effects on Elk With the wolves gone, the elk population grew too quickly. Thousands of elk starved because there was not enough food to feed them all.
Too Many Elk! There were too many elk. Park rangers finally had to shoot and kill the elk, to keep their population down.
Too Many Coyotes! Wolves are natural predators of coyotes. When the wolves left, the coyote population also grew.
Effect on Smaller Predators The coyotes ate too many small animals, which other predators in Yellowstone (like foxes and badgers) eat.
Effects on Foxes and Badgers The foxes and badgers populations decreased, because the coyotes were taking all of their food.
Effeccts on Pronghorn Deer Coyotes also eat baby Pronghorn deer. The Pronghorn population declined and almost disappeared.
Effects on Trees Plants were also affected. Elk love to eat saplings (young trees) like aspen, cottonwood, and willow trees.
Effects on Birds Too many elk ate the saplings, so there were fewer trees. This means that were fewer homes for the birds that lived in the trees.
No Homes for Birds! The bird population of Yellowstone decreased, because there was no place for them to live.
Effects on Beavers Beavers eat trees. As the trees disappeared (eaten by the elk), so did the beavers.
The Ponds Disappear Beavers build dams that form ponds. Fewer beavers meant no ponds, and this meant no homes for the dragonflies and ducks that lived in the ponds.
Can the Problem Be Solved? The park rangers finally realized they had a big problem. They decided that maybe wolves needed to come back.
The Wolves Come Back In 1995, seven wolf packs were captured in Canada and brought to Yellowstone.
Cause / Effect Flow Chart Now, as you read the next sections, fill in the cause & effect chart to show what happened to the Yellowstone ecosystem after the wolves came back.
When the Wolves Returned
Wolf Prey The wolf packs quickly spread out and began hunting for their favorite foods elk and coyote.
Wolf Population Grows With lots of elk and coyote to eat, the wolf population grew quickly. There are now about 150 wolves in the park.
Effect on Coyotes Wolves hunted and killed about half of the coyotes. Now, the coyotes stay away from the wolves.
Effect on Pronghorn Deer With fewer coyotes, more Pronghorn fawns are able to survive. The Pronghorn population is growing!
Effect on Smaller Predators With fewer coyotes, smaller predators such as foxes, owls, and badgers, now have food to eat.
Effect on Elk The wolves are also helping to control the elk population. Now, there are not as many starving elk.
Effect on Trees Because there are less elk eating the trees, the trees are starting to grow big and tall again.
Effect on Birds With more trees, there are more homes for birds. The birds are coming back to Yellowstone.
Effect on Beavers Because there are more trees, the beaver population has grown larger.
Effect on Ponds The beavers are building dams again, creating ponds that dragonflies and ducks can live in.
So, are wolves bad? People thought wolves were mean creatures that ate peaceful animals.
Why are wolves important? But now we know that wolves NEED to hunt their prey, or there will be too many prey animals.
Wolves are part of the ecosystem. Wolves are an important part of the Yellowstone ecosystem.
Wolves affect the ecosystem. When the wolves were gone, it affected many, many other organisms animals and plants both.
A Healthy Ecosystem Again! Now that the wolves are back, the Yellowstone ecosystem is getting back into balance. It is becoming healthy again!
ALL organisms are important. EVERY organism in an ecosystem is important. EVERY organism affects the ecosystem community.
Why are YOUR ecosystem s predators important? You are studying an ecosystem. Choose a predator in your ecosystem. How might YOUR ecosystem be affected if that predator were gone? Write at least 2 possible cause/effect ideas on your answer sheet.