TEACHING ALL VOLUMES SUBMIT WORK SEARCH TIEE
VOLUME 6: Table of Contents TEACHING ISSUES AND EXPERIMENTS IN ECOLOGY
ISSUES: FIGURE SETS

Figure Set 4: How do wolves impact elk and elk browsing, if not by direct population control?

Purpose: To introduce the idea of indirect effects of predator on prey by changing prey behavior, and of trophic cascades - effects of predators on primary producers; to construct a flow diagram of effect of prey behavioral response to predation on vegetation; to use concept mapping to construct a complex food web for the Greater Yellowstone Ecosystem.
Teaching Approach: informal group work
Cognitive Skills: (see Bloom's Taxonomy) — knowledge, comprehension, interpretation, application, synthesis
Student Assessment:flow diagram and (optional) concept map

BACKGROUND

How do wolves impact elk and elk browsing, if not by direct population control?

This final segment of the issue introduces the notion of indirect effects of predators on prey, and of predators on other components of the food web and ecosystem via trophic cascades. Ripple and Beschta (2004a,b) proposed that wolf restoration may not have a very strong effect on elk population sizes, but it does have a very strong effect on elk behavior, in that it is no longer safe for the elk to hang out and browse in the riparian areas where food is abundant, because cover for their predators is also abundant. Enclosed areas, stream banks, and short sight-distance make the riparian areas more risky than open upland sites. Increased vigilance on the part of the elk, and the "ecology of fear" (Ripple and Beschta 2004b) turn out to be the "saving grace" for woody riparian vegetation, and for a suite of other organisms that rely on the health of that vegetation.

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