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Yellowstone Food Web

Grade Level: 4-6



Yellowstone National Park is a region with abundant and diverse wildlife. Students will learn from the video, The Living Edens: Yellowstone (PBS), that each animal has a niche in this ecosystem as a predator, prey, and/or scavenger. Each animal is dependent on others for its own survival, and the predator/prey/scavenger relationship balances the ecosystem so that no one animal overpopulates the whole park. Wolves and bears are at the top of the Yellowstone food chain, and prey on other animals such as elk and bison. Other predator/prey relationships include the fox/mouse and otter/fish. Coyotes and ravens are common scavengers in Yellowstone.


Students will:
  • investigate the interdependence of wildlife in the Yellowstone ecosystem.
  • define the following terms: predator, prey, scavenger, herbivore, carnivore, omnivore, ecosystem, and interdependence.
  • draw an ecosystem showing the interdependence of life forms.

National Standards:

National Science Education Standards
Life Sciences: Populations and Ecosystems
  • The number of organisms an ecosystem can support depends on the resources available and abiotic factors, such as quantity of light and water, range of temperatures, and soil composition. Given adequate biotic and abiotic resources and no disease or predators, populations (including humans) increase at rapid rates. Lack of resources and other factors, such as predation and climate, limit the growth of populations in specific niches in the ecosystem.
  • For ecosystems, the major source of energy is sunlight. Energy entering ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis. That energy then passes from organism to organism in food webs.
  • Populations of organisms can be categorized by the function they serve in an ecosystem. Plants and some micro-organisms are producers--they make their own food. All animals, including humans, are consumers, which obtain food by eating other organisms. Decomposers, primarily bacteria and fungi, are consumers that use waste materials and dead organisms for food. Food webs identify the relationships among producers, consumers, and decomposers in an ecosystem.

  • The Living Edens: Yellowstone (PBS video)
  • large white construction paper or poster board
  • lined paper and pencil for each student
  • ball of string
  • tape


Make placards with the name of each animal mentioned in the video on a piece of construction paper (see list of animals below). Make two other placards for water and grass.

  1. Begin lesson by eliciting from the class the definitions of predator, prey, scavenger, herbivore, carnivore, omnivore, ecosystem, interdependence. Write the words and their definitions on the board.
  2. Have each student divide a piece of lined paper into seven columns and write headings for the columns in this order from right to left: Animal, Predator, Prey, Both, Scavenger, Herbivore, Carnivore, Omnivore. Instruct the students to make a list of the animals that they see in the video in the Animal column. As they write each animal they are to make a checkmark in the other appropriate columns to show if the animal is a predator, prey, or both. They will then make a checkmark in the appropriate column indicating whether it is an herbivore, carnivore, or omnivore. When the video is done, review the answers and add any that were not mentioned.
The video highlights:
  • elk (05:11-07:46; 30:52-37:28; 45:37-46:59)
  • wolves (05:11-07:46; 25:00-26:40)
  • coyotes (07:46-10:21; 25:00-26:40)
  • bison (12:56-14:30; 23:00-25:00; 42:46-45:37)
  • grizzly bear (18:29-19:53; 27:00-37:28)
Other animals that are shown with less emphasis:
  • mice and fox (10:21-11:50)
  • ravens (07:46-10:21)
  • bald eagles (07:46-10:21)
  • mountain lion (21:00-23:00)
  • osprey (38:27-39:55; 42:26-44:36)
  • cutthroat trout (39:55-42:26)
  • otters (41:04-42:26)
  • bees, butterflies and flies (37:28-38-27)
More information on these animals can be found on the Featured Creatures page of this Website.
  1. Divide the class into groups of four. Each group will use construction paper to draw a panoramic view of Yellowstone that includes each of the habitats: mountain, meadow, and stream. They will then draw the animals that were in the video in their respective habitats. Students draw lines connecting animals that have a dependence on another animal. For example, a line should be drawn from the bear to the fish and a line from the fish to an insect, etc.
  2. Have the class form a circle around the room. Each student will pick a placard labeled water, grass, or one of the animals from the set of placards prepared ahead of time. They attach the placard to their shirts using tape. Give the student who is the wolf the ball of string and have him/her hold the end while unwinding the ball and passing the rest of the string to another animal that he needs, or who needs him, in order to survive (as viewed in the video). That person in turn holds onto the string while unwinding the ball and passing the ball on to the animal that his animal needs, or needs him, to survive. For example, the student who is the fish could either pass the ball of string to the insect (who he needs to survive) or to the bear (who needs the fish in order to survive). As each person holds the string, unwinds the ball, and passes the ball on, the string begins to make an overlapping web connecting each life form until all animals and plants have been connected. Some animals may be used more than once since they eat, or are eaten by, more than one animal, resulting in a very complex web that is typical of nature.
  3. Ask the class which animal they think is least important in the web. Whoever has that placard has to drop his string and is now considered to be extinct. Any animal that was connected to that animal by string must also let go of his string because the animal that he is connected to is no longer part of the ecosystem and cannot help these animals survive. The next group of animals has to drop out also for the same reason until each animal has successively dropped out of the web. Students realize that no animal can survive on its own; if one drops out of the food web, they all eventually drop out, showing the delicate balance of an ecosystem.

Assessment Suggestions:
  • Ability to work cooperatively in a group
  • Participation in class discussions
  • Completion and accuracy of ecosystem drawing
  • Ability to define predator, prey, scavenger, herbivore, carnivore, omnivore, ecosystem, and interdependence

  • Research the similarities and difference between wolves and coyotes. In pairs, students will make a Venn diagram showing to compare and contrast these animals.
  • Research efforts to control coyote populations and hold a class debate on the pros and cons of the government trying manage coyote populations.
  • Compare the Yellowstone ecosystem to other national park ecosystems (i.e., Biscayne National Park, Death Valley National Park, Grand Canyon National Park)
  • Further explore predator/prey relationships through The Wolf and the Moose (change it to wolf and elk) activity from
  • What Denali Animal Am I?(change to What Yellowstone Animal Am I from


Web Resources: NOVA: Wild Wolves

NOVA: American Buffalo

Nature: Yellowstone Otters

Printed Material:

Wexco, J.B., 1988, Zoobooks: Little Cats, Wildlife Education, Ltd.
Wexco, J.B., 1991, Zoobooks: Little Birds of Prey, Wildlife Education, Ltd.
Biel, T.L., 1988, Zoobooks: Wild Dogs, Wildlife Education, Ltd.
Biel, T.L., 1988, Zoobooks: The Deer Family, Wildlife Education, Ltd.
Wexco, J.B., 1988, Zoobooks: Wolves, Wildlife Education, Ltd.
Wikinson, Wildlife Watcher's Guide -- Yellowstone and Grand Teton National Parks
Consolo-Murphy, S., and Murphy, K., Wildlife at Yellowstone: the Story Behind the Scenery
Craighead, Large Mammals of Yellowstone and Grand Teton National Parks
McEneaney, T., Birds of Yellowstone



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