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Search for the Missing Sea Otters

An Ecological Detective Story


Mary Allen
Department of Biology
Hartwick College
Mark L. Kuhlmann
Department of Biology
Hartwick College


Using a progressive disclosure format, this case study teaches students how to apply ecological principles to a real-life ecological problem, namely, the decline in sea otter populations in Alaska. Students interpret data from graphs and tables and practice developing testable hypotheses as they work in groups to solve the mystery of the “missing” sea otters.  Designed to serve as a framework for teaching an ecology module to first-year biology majors, the case introduces students to basic concepts of population and community ecology.


  • Interpret data from graphs and tables.
  • Practice developing testable hypotheses.
  • Understand indirect effects in biological communities.
  • Learn about sea otter, killer whale, and kelp forest ecology.


Sea otter; killer whale; Orcinus orca; marine mammal; population ecology; community ecology; kelp bed; predator; predation; ecological energetics; Alaska

Topical Areas

Scientific method

Educational Level

High school, Undergraduate lower division



Type / Methods

Discussion, Interrupted



Subject Headings

Ecology  |   Environmental Science  |   Biology (General)  |   Zoology  |   Marine Science / Oceanography  |  

Date Posted


Teaching Notes

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Supplemental Materials

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

  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.