NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
CASE TEACHING NOTES
for
“The Effects of Coyote Removal in Texas:
A Case Study in Conservation Biology“
by
Margaret Carroll, Department of Biology, Framingham State College
INTRODUCTION / BACKGROUND
This case, suggested by Ommundsen (2000), presents
data from Henke and Bryant (1999) on the effect of
coyote removal in Texas. It is designed to help students
in introductory level biology courses understand trophic
level relationships and the role of keystone species.
Students are required to interpret data that are presented
graphically and to predict how changes at one trophic
level may affect populations and communities at other
trophic levels.
I use this case in the lecture portion of an introductory
biology course for non-majors. This course generally has
about 72 students, many of whom have poor math skills
and difficulty graphing and interpreting data. They are
often quite science phobic.
The use of case studies in this course reinforces basic
concepts from lecture and helps the students develop
reasoning skills. The students in Fall 2000 reported (on a
scale of 1= strongly disagree to 5 = strongly agree) that case
studies helped them to understand the scientific process
(mean = 4.1, N=39) and to see how material from the
course could be applied (mean = 4.3, N = 39). Students
feel case studies are a useful addition to the course (mean
= 4.3, N = 63 on a scale of 1–5, with 5 being very useful).
I use the coyote removal case study after introducing
basic ecological principles. Students rate this case as
very useful (mean = 4.4, N=64); it helps to solidify
their understanding of ecological principles and the
application of those principles to conservation.
I run this case as an in-class discussion that generally
takes two 50-minute class periods. The case is presented
with PowerPoint®, as described in the “Classroom
Management” section below.
Objectives
• Emphasize the importance of keystone predators. I
usually introduce the keystone species concept using
the example of the starfish Pisaster (Paine 1974). This
case helps the students to see that there are other
examples and that this concept has application in
conservation biology.
• Demonstrate the difficulty of predicting the
effects of ecological perturbations. When students
work through this case, they will be able to make
predictions about the effects of specific changes and
should be able to articulate the reasoning behind
their predictions. As the entire class discusses each
question, the students will find that they can make
equally well-reasoned arguments for dramatically
different effects.
• Challenge students to interpret data that are
presented graphically. Students in this course prefer
to wait for the meaning of a graph to be explained.
Lively discussions generally arise when they are
asked to interpret these graphs as a group.
• Emphasize the importance of appropriate
experimental controls. Students quickly realize that
the changes in the control plots are not the result of
coyote removal. It is useful to have the students make
a list of factors other than coyote population size that
could cause changes in the animal communities.
CLASSROOM MANAGEMENT
I present cases in this course with PowerPoint® using
the progressive disclosure method as described by
Colyer (2000). The slides present details of the case in
outline form. I made a simplified food web using the
organization chart feature of PowerPoint® to present the
trophic relationships in the community. It is useful to
have this chart on an overhead that can be left up for the
students to refer to throughout the exercise. In the original
paper, the authors discuss coyote control, and to avoid
confusion they use the term “comparison area.” When I
scanned the graphs I changed the terminology to coyote
Case Teaching Notes for “The Effects of Coyote Removal in Texas” by Margaret Carroll
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NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
removal and control areas. I made these changes because
I wanted to discuss the importance of experimental
controls without confusing the students. The modified
graphs are presented with relevant questions directly on
the slide.
I have prepared response forms for the students
on which I reprint the questions from the case. (An
example form is attached to the end of these notes.) The
students work in groups of four or five; each group is
required to fill out a response form. The students are
given approximately 10 to 15 minutes to answer each set
of questions; we then discuss them as a group. I make
a list on the board of all student responses; it is useful
to list responses in table form in order to link related
material, as in the first three questions.
Ensuring that all students participate is difficult in a
class this size. It is essential that the students realize that
all groups will be called on for answers, even those that
do not volunteer. I try to start with a different group
for each set of questions, then ask others to add new
information. I require that the students hand in the
response form with all of the team members listed at the
end of the case. Students who miss one day of a two-day
case, or who arrive substantially late, can earn no more
than half credit for the case.
username and password. If you have not yet registered
with us, you can see whether you are eligible for an
account by reviewing our password policy and then
apply online or write to answerkey@sciencecases.org.
REFERENCES
Colyer, C. 2000. Death in a Viennese Maternity Ward:
Childbed Fever—A Nineteenth Century Mystery.
Journal of College Science Teaching 29:297–300.
Also available at http://sciencecases.lib.buffalo.edu/
center/.
Fortier, G.M. 2000. The Wolf, the Moose, and the Fir
Tree: A Case Study of Trophic Interactions. Journal
of College Science Teaching 30:92–95. Also available
at http://sciencecases.lib.buffalo.edu/center/.
Henke, S.E., and F.C. Bryant. 1999. Effects of coyote
removal on the faunal community in Western Texas.
Journal of Wildlife Management 63:1066–1081.
Ommundsen, P. 2000. Problem-based learning in biology
with 20 case examples. http://www.saltspring.com/
capewest/pbl.htm.
Paine, R.T. 1974. Intertidal community structure:
Experimental studies on the relationship between
a dominant competitor and its principal predator.
Oecologia 15:93–120.
Follow-up Exercises
Some instructors may want to include follow-up exercises
on predator populations in their local areas. Predator
populations in many suburban areas are increasing as is
the frequency of human encounters with these animals.
Students could investigate local problem predators and
their preferred prey species. They could be required to
write an essay (or a letter to a legislator) concerning the
possible impacts of the increasing predator population
and its proposed removal.
The case study of Isle Royale trophic interactions
(Fortier 2000) would be a good partner for this case. This
pairing would allow students to see that communities are
unique in their response to environmental manipulation.
These two cases are written at different levels; therefore,
one would have to be adjusted depending on the
intended audience.
ANSWER KEY
Answers to the questions posed in the case study are
provided in a separate answer key to the case. Those
answers are password-protected. To access the answers
for this case, go to the key. You will be prompted for a
•
Acknowledgements: Publication of this case study on the
National Center for Case Study Teaching in Science
website was made possible with support from The Pew
Charitable Trusts.
Copyright held by the National Center for Case
Study Teaching in Science, University at Buffalo, State
University of New York. Originally published February 25,
2002. Please see our usage guidelines, which outline our
policy concerning permissible reproduction of this work.
Case Teaching Notes for “The Effects of Coyote Removal in Texas” by Margaret Carroll
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NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
RESPONSE FORM FOR COYOTE REMOVAL CASE STUDY
Team Members
1. ________________________________
4. ________________________________
2. ________________________________
5. ________________________________
3. ________________________________
6. ________________________________
Part I – Introduction
1. What specific question do you need to answer?
2. What variables will you monitor?
3. What type of controls will you use?
Part II – Experimental Design
4. Make two predictions concerning the effects of coyote removal.
i.
ii.
Part III – Mesopredators
5. What effect does coyote removal have on the mesopredator populations?
6. What do think might have happened to the rodent populations?
NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
Part IV – Rodent Population Size
7. What is the primary factor controlling rodent population growth?
8. What other changes might you expect in the rodent community?
Part V – Rodent Diversity
9. In one sentence summarize the meaning of the graph shown in Figure 4.
10. How does the competitive success of Ord’s kangaroo rat change in the absence of coyotes?
11. What term could be used to describe the role of the coyote in this community?
12. Propose one possible cause for the decline in rodent diversity in the control areas after treatment begins.
13. What would be the significant impact of coyote removal in this community?