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Investigative Case - "Rio Grande Wildlife Refuge"

Developed for Lifelines Online by Wayne McMillan of Garden City Community College and Mark A. Storey of Texarkana College. (www.bioquest.org/lifelines ( This site may be offline. ) )
This material is replicated on a number of sites as part of the SERC Pedagogic Service Project


Picture of an ocelot
As professional ecologists working for the fish and wildlife service, students must develop a plan to manage a new wildlife refuge along the Rio Grande River. The fish and wildlife service plans to connect forest islands along the river, which will become not only a new refuge but also a "wildlife corridor."

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Learning Goals

  • Introduce the discipline of Ecology in a practical manner.
  • To look at wildlife management as it relates to ecological principles and whole systems.
  • To introduce students to the global concern of 'patchy' environments.
  • To familiarize students to survey techniques.

Context for Use

This case is appropriate for an advanced High School or entry level majors Ecology course. The course involves individual and group work ans has a field work component if suitable sites are available.

Considering Class Size - Different types of objectives can be accomplished by implementing case-based learning in different sized classes.

How Do Investigative Cases Fit into Courses?- What issues need to be taken into account before introducing cases to your class?

Teaching Materials

You are a professional ecologist working for the fish and wildlife service, and have been given an assignment to manage a new wildlife refuge along the lower Rio Grande River. It is an unusual refuge since a portion of it must be "constructed". The fish and wildlife service plans to connect forest islands along the river, which will become not only a new refuge but also a "wildlife corridor."

This will be an enormous project, since the refuge will encompass 250 river miles from Falcon Dam to Laguna Atascosa National Wildlife Refuge at the Gulf Of Mexico. The "corridors" main purpose is to preserve species diversity. Ten distinctly different wildlife communities exist along the river, and are critical for the survival of 115 species of birds and mammals.

Several endangered species are found within these communities including the ocelot, and jaquarundi. These communities are the northern most range of many central and South American species. Other species include the green jay, the hooked bill kite, ferruginous pygmy owl and fulvous whistling duck.

By connecting islands of forests, animals will be able to move and have access to a larger forested area. One of your objectives will be to acquire 135,000 acres of privately owned forested and deforested land along the river. Building a "wildlife corridor" is a concept that relates to an ecological principal called "Island Biogeography theory.

An initial study is needed to obtain estimates of species richness and relative abundance of birds, mammals, reptiles and amphibians in experimental and control plots. Experimental plots should be narrow one hundred meter wide "corridor-like" forest patches. Control plots of similar habitat should be large (approximately 500 acres).

You will also have to do a base line study of animal numbers and species in all existing forest islands. Breeding birds should be sampled by point count technique. Small mammals, reptiles, amphibians and some invertebrates should be sampled by pitfall array and Sherman live trap grids.

Questions for Discussion
  1. Why is it necessary to preserve communities for key species?
  2. Why should we use ecological theory in wildlife management?
  3. If no protection plan is implemented how will species diversity be affected in these communities?

Investigative Activities
  • Web site search of key words found in the case scenario and background
  • Bio-Quest Eco-Beaker Introductory sampling modeling activity
  • Field Study on bird diversity in Shelter Belts - Shelter belts provide a unique opportunity to evaluate Island Biogeography theory for two reasons:
    1. Man made habitats with similar structural configurations.
    2. Represent small (0.1- 2.9 ha) forest islands. Small islands provide a unique situation because some bird species can be precluded from colonization due to territorial size requirements.

Teaching Notes and Tips

How To Use Investigative Cases with Examples - This area of the site lays out the phases Investigative Case Based Learning and key strategies for using it in your class.

Preparing Students for Cases and Collaborative Learning - Hints and advice on how to introduce cases into your class.


  • Each student will submit a report which should include the following:
    1. What is Island Biogeography Theory (IBT)?
    2. How does IBT relate to the size of forest islands and the maintenance of species diversity?
    3. How might the data from your initial study of species numbers and richness (scenario) be used?
    4. Why is it important to facilitate movement between patches and what effect can isolation have on species?
    5. What is an egg parasite and how would it effect birds in forest islands?
  • Submit group reports based on the Bio-Quest Eco-Beaker introductory sampling simulation program.
  • Develop and present a group poster pertaining to the "Wildlife Corridor Concept"

References and Resources