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Case Study on Wolves in Yellowstone

Page history last edited by barbara gibson 6 years, 1 month ago


You and your group will study the literature and the data provided below to craft a Management Plan for wolves in Yellowstone Park.  In your plan you must satisfy the National Park Service/Yellowstone Wolf Project as well as the local ranchers and the Wyoming Fish, Wildlife and Parks Commissions.  Please to be creative and thorough.  Use the data and resources provided as well as any other outside scientific resources you come across that are relevant. In your final presentation you must include the correct use of the terms trophic cascade, carrying capacity, interspecific/intraspecific competition, density dependent factors, density independent factors, keystone species and food web.


Resources and Activities

Phase 1- Background

Packs of wolves once roamed throughout North America. Gradual loss of habitat from westward expansion as well as extermination programs by local and national governments led to their demise and eventual extinction in the United States (Smith et al. 1999). These programs were implemented because wolves were viewed as dangerous predators. However, it is argued that predators provide benefits to a naturally functioning ecosystem. One of the natural ecosystems that seemed to be missing the impact of wolves as major predators was the Greater Yellowstone Area, specifically Yellowstone National Park (YNP). By 1926, there were no gray wolf packs in YNP. In 1995, following years of extensive planning, wolf restoration to YNP began when wolves were brought from Canada to YNP to be released. This decision was not without major controversy, which continues today. 





Your job as a research team is to investigate the background of this wolf restoration by reading the articles below. After every group member has been briefed on the background, you should start analyzing the arguments from both sides of the issue. Based on the information from the articles, you should fill in the chart below with the pros and cons of having wolves in an ecosystem.



      print out and complete: pros and cons for wolf reintroduction.pdf




Phase 2 - Data  
Using the data provided, answer the following questions.  

1. Is there a correlation between the number of wolves and the number of wolf packs?

2. Define the term carrying capacity.  From the data, what would you assume is the approximate carrying capacity of wolves in the Yellowstone?

3. Do livestock losses correlate with wolf population changes?

4.  Do changes in the the elk population track changes in the wolf population?

5. What might be the limiting factors for wolf? for elk?

Table 1. Numbers of wolves and numbers of packs at the end of each year Yellowstone Wolf Project Annual Reports 1995-2011


Table 2. Livestock Predation

Graph 1. Wolf and Elk Count  



Phase 3 - Your Management Plan Presented    

You should now have a basic knowledge of the wolf reintroduction debate. There are good arguments on both sides of the issue. The previous information has addressed some of the things biologists have learned about wolves since their reintroduction. But questions remain concerning whether wolves have helped stabilize the Greater Yellowstone Ecosystem or whether they have caused more harm than good. Was there really a need for the reintroduction? These are some of the questions that are central to a debate about how to manage this population of wolves.


Your job is to create a management plan that not only stresses the importance of wolves as a keystone species to this ecosystem, but also satisfies both sides of the controversy: the National Park Service/Yellowstone Wolf Project and the local ranchers/specific state departments (i.e., Fish, Wildlife, and Parks Commissions). Your plan will be in the form of a presentation. Please try to be creative and thorough. You should use the information and sources from this case and any other scientific articles you can find. Please cite your sources.


In your plan, you should also incorporate and explain the following terms that were introduced in Parts I–III:

  • Trophic cascade 
  • Carrying capacity
  • Density dependent/independent factors (related to population growth)
  • Keystone species
  • Exponential Growth
  • Predator-prey relationship
  • growth rate - r 


As a part of your presentation, prepare a graph that you believe accurately shows the current and future growth of the wolf population in Yellowstone, assuming they reach carrying capacity. Include a best fit exponential growth equation as part of the graph. Based on the theoretical carrying capacity, how many cows and sheep would be expected to be killed if the wolf population reached carrying capacity?


                                                                                                                                                                    (back to Population Ecology)

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