Isle Royale Predator-Prey Cycle
Jenn Carlson, Lake Orion High School
Standards:
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B3.5A Graph changes in population growth,
given a data table.
B3.5B Explain the influences that affect
population growth.
B1.1D Identify patterns in data and relate
them to theoretical models.
L3.p3D Predict how changes in one population might affect other populations based
upon their relationships in a food web.
(prerequisite)
Grade/Class:
9th Biology
Objective:
Students will be able to construct and interpret a
predator prey graph.
Assessment:
Labeled graph (7 points) and critical thinking
questions (8 points)
Materials:
Class set of worksheets, slide show of Isle Royale
research photos
Procedure:
In this application, students will apply their
knowledge of predator prey cycles to the Isle
Royale wolf and moose populations.
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Engage:
Brief slide show of my own photos showing Isle
Royale and Rolf Peterson’s research to introduce
them to the island and the study (pages 150-151 in
A Superior Wilderness discusses this research).
Explore:
Students will complete the attached worksheet
where they will construct a predator prey graph
and then interpret it. Enclosed are both the original data from (www.isleroaylewolf.org) and a
simplified data table. I will have my students use
the simplified data so they can draw the graph by
hand. It shows the same trends as the original
data, but does not need to be graphed in Excel.
They will need to use dual y-axes to show the
trend, since moose numbers are so much greater
than wolf numbers. The left y axis should be in
increments of 10, from zero to 50 for the wolves.
The right x axis should be in increments of 500,
from zero to 2500. Each y axis will have 5 increments – see answer key for correct set-up. Explain to students that they are able to have different increments because they are comparing a
trend, not exact quantities. Encourage students to
use their notes from Gray Wolves/Gray Matter and
the brochure they received yesterday to answer the
critical thinking questions.
Explain:
Discuss the students’ answers the worksheet. Fill
in any holes to the story of the wolves and moose
of Isle Royale they may have missed.
MSTA Journal
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Fall 2007
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http://www.msta-mich.org
Extend:
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Ask students to think about other factors that may
affect the population cycles of wolves not on Isle
Royale. Researchers believe that vegetation may
affect moose numbers significantly (seen in the
1990s), and also disease, such as the canine parvo
virus, has affected the wolf population (seen in the
1980s).
Bibliography:
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Peterson, Rolf and John Vucetich. The
Wolves and Moose of Isle Royale. 2006.
Michigan Technological University. 21 Aug.
2006. <http://www.isleroyalewolf.org/>
This website provided the data. It also has a
number of other resources about the wolves
and moose of Isle Royale. The authors of
this website are the scientists conducting the
research.
MSTA Journal
•
Fall 2007 •
http://www.msta-mich.org
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Peterson, Rolf and John Vucetich. The
Wolves and Moose of Isle Royale Brochure.
Michigan Technological University. This is a
brochure that I received while on Isle Royale,
discussing the wolf and moose populations in
a concise way.
Shelton, Napier. Superior Wilderness: Isle
Royale National Park. Houghton, MI: Isle
Royale Natural History Association, 1997.
I used this book for the chapter “Wolves,
Moose, and the Balance of Nature;” however,
it also covers many other Isle Royale topics.
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Wolf and Moose Populations on Isle Royale
Graph the following data of the wolf and moose population on Isle Royale. Use dual y-axes to show the
trend, since moose numbers are so much greater than wolf numbers. The left y axis should be in increments of 10, from zero to 50 for the wolves. The right x axis should be in increments of 500, from zero to
2500. Each y axis will have 5 increments. Be sure to label and title your graph.
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Year
Wolves
Moose
1959
20
563
1966
26
765
1969
17
1268
1970
18
1295
1973
24
1435
1977
34
1143
1978
40
1001
1981
30
863
1982
14
872
1983
23
932
1985
22
1115
1990
15
1216
1995
16
2422
1996
22
1163
1998
14
699
2001
19
900
2002
17
1100
2003
19
900
2006
30
450
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Fall 2007
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Critical Thinking Questions
1. Can an ecosystem support an infinite number of moose? Why or why not? __________________
______________________________________________________________________________
2. If wolves did not live on Isle Royale, what main factor would determine the amount of moose the
island could support? ____________________________________________________________
3. What other factors may influence population numbers? _________________________________
______________________________________________________________________________
4. Is predation a density-dependent or density-independent factor? __________________________
______________________________________________________________________________
On Isle Royale, the moose have a predator – the wolf. Use your graph to answer
the following questions.
5. When the moose (prey) population increases, what happens to the wolf (predator) population?
Why? ________________________________________________________________________
______________________________________________________________________________
6. What causes the moose population to decrease? When this happens, what happens to the wolf
population? ___________________________________________________________________
______________________________________________________________________________
7. Why is this interaction between predator and prey called a cycle? _________________________
______________________________________________________________________________
8. Why is this cycle so easily studied on Isle Royale? ______________________________________
MSTA Journal
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Fall 2007 •
http://www.msta-mich.org
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Answer Key
Wolf and Moose Populations on Isle Royale
1.
2.
3.
4.
5.
No – limiting factors/carrying capacity
Food supply
Predation, Competition, Natural Disasters, Disease, etc
Density-dependent
Wolf population increase because it has more food (Bonus—disease may cause the wolf population to decrease even if the moose population is increasing, as canine parvo virus did with the Isle
Royale wolves in the 1980s)
6. The moose population will decrease as there are more predators hunting it. Eventually the wolf
population will decrease because it will run out of moose to eat (Bonus—the moose population
may also decrease if the population becomes too high for the amount of food available, as happened at Isle Royale in the 1990s)
7. Because this pattern will continue to repeat itself – it maintains a balance
8. Because the number of variables is decreased and the populations are more easily monitored because of the small, contained space
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MSTA Journal
•
Fall 2007
•
http://www.msta-mich.org