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The Effects of Coyote Removal in Texas

A Case Study in Conservation Biology


Margaret A. Carroll
Department of Biology
Framingham State College


This interrupted case study presents published data on the effect of coyote removal in Texas. It was designed to help students in introductory level biology courses understand trophic level relationships and the role of keystone species. Students interpret data presented graphically and predict how changes at one trophic level may affect populations and communities at other trophic levels.


  • Understand the importance of keystone predators. 
  • Demonstrate the difficulty of predicting the effects of ecological perturbations.
  • Interpret data that are presented graphically.
  • Learn about the importance of appropriate experimental controls.


Coyote; predator control; top predator; mesopredator; trophic cascade; keystone species; conservation biology; experimental design; West Texas

Topical Areas


Educational Level

High school, Undergraduate lower division



Type / Methods

Interrupted, Journal Article



Subject Headings

Ecology  |   Wildlife Management  |   Environmental Science  |  

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.