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The Return of Canis lupus?


Parks Collins
Natural Science
Mitchell Community College


Although gray wolves once freely roamed North America, the gradual loss of their habitat from westward expansion and extermination programs led to their demise in the early 20th century. Many argue that predators such as wolves benefit a functioning ecosystem. In 1995, following years of extensive planning and controversy, wolves were brought from Canada and restored to Yellowstone National Park. This case study provides students with an opportunity to integrate various abstract ecological concepts (trophic cascades, keystone species, interspecific versus intraspecific interactions) with applied ecology as they learn about the wolf reintroduction debate and the conservation of an ecosystem. As part of their case work, students formulate and present a management plan. Originally designed for a college ecology course, this case has also been successfully used with both majors and non-majors in basic biology courses. Students will need some background knowledge of community and population structure within ecosystems.


  • Explain ecological concepts as they are set in the context of an ongoing controversy.
  • Differentiate between interspecific and intraspecific interactions.
  • Differentiate between density-dependent and density-independent factors as they relate to population size.
  • Define carrying capacity.
  • Understand how wolves are linked to a trophic cascade mechanism.
  • Understand why the wolf is considered a keystone species.
  • Analyze data sets.
  • Develop literature review skills.
  • Apply information from research and behavior to a management plan.


Wolf; wolves; Canis lupus; animal behavior; trophic cascade; carrying capacity; interspecific competition; intraspecific competition; density-independent factors; density-dependent factors; keystone species; food web; community; Yellowstone National Park

Topical Areas

Ethics, Regulatory issues

Educational Level

High school, Undergraduate lower division, Undergraduate upper division



Type / Methods

Analysis/Issues, Discussion, Interrupted, Student Presentations



Subject Headings

Ecology  |   Wildlife Management  |   Biology (General)  |  

Date Posted


Teaching Notes

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Supplemental Materials

The supplemental material below may be used in conjunction with this case.

  Click-and-Learn: Exploring Trophic Cascades hhmi/

Answer Key

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The following video(s) are recommended for use in association with this case study.

  • Some Animals are More Equal than Others hhmi/
    This short film opens with two questions: "So what determines how many species live in a given place? Or how many individuals of the species can live somewhere?" The research that provided answers to these questions was set in motion by key experiments by ecologists Robert Paine and James Estes. The film discusses Paine's starfish exclusion experiments on the coast of Washington state as well as Estes' and colleague John Palmisano's discovery that the kelp forest ecosystems of the North Pacific are regulated by the presence or absence of sea otters, which feed on sea urchins that consume kelp. These early studies were the inspiration for hundreds of investigations on other keystone species and trophic cascades, as well as ongoing studies into the regulation of population sizes and species numbers. Running time: 19:29 min. Produced by HHMI BioInteractive.
  • Film Guide for "Some Animals are More Equal than Others" hhmi/
    Film guide as well as instructor materials and a student quiz that complement the film "Some Animals Are More Equal Than Others: Trophic Cascades and Keystone Species." Produced by HHMI BioInteractive.


Jessica Labbe

Bremen High School
I was wanting to discuss with someone who had used this case study on a high school level and bounce some ideas off of you for direction with students on writing the management plan.