Investigative Case - "Rio Grande Wildlife Refuge"

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.