Predator Management Activity
Purpose: To determine the effect of predation and how it can change the amount of energy in an
ecosystem.
Background:
In 1970, the deer population of an island forest reserve about 518 square kilometers in size was
about 2,000 animals. Although the island has excellent vegetation for feeding, the food supply
obviously had limits. Thus, the forest management personnel feared that overgrazing might lead to
mass starvation. Since the area was too remote for hunters, the wildlife service decided to bring in
natural predators to control the deer population. It was hoped that, eventually, natural predation
would eliminate the weakest deer, thereby preventing the herd from becoming too large and, at the
same time, increasing the quality of the herd. In 1971, 10 wolves were flown into the island. The
results of this natural predator program are presented in Table 1.
Choose one
Hypothesis: If predators are introduced into an ecosystem then they will have (no, a large, little) effect
on an ecosystem because . . . . . (explain why).
Background Questions: Answer the following questions in complete sentences, making sure to restate
the question within your answer.
1.
2.
3.
4.
How are the following words related: predation, predator and prey?
What was the wildlife service afraid of from the deer population?
What did the wildlife service try to do in order to control the deer population?
Should humans be allowed to control the population of a species like they tried to in this situation?
Why or why not?
Materials:
population table
graph paper
ruler
color pencils
Procedures:
1. Plot the fluctuations (changes) in the deer and wolf population. Create a line graph of the data and
use a different color for the wolf and deer populations. The first three columns (years, wolf
population, & deer population) of Table 1 will be graphed.
Data Table 1: Population table
Year
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
Wolf
Population
10
12
16
22
28
24
21
18
19
19
Deer
Population
2000
2300
2500
2360
2244
2094
1968
1916
1952
1972
Deer
Offspring
800
920
1000
944
996
836
788
766
780
790
Predation
Starvation
400
480
640
880
1120
960
840
720
760
760
100
240
500
180
26
2
0
0
0
0
Population
Change
+300
+200
-140
-116
-150
-126
-52
+46
+20
+30
1800 1900 2000 2100 2200 2300 2400 2500 2600
30
Key:
Wolf Population
Deer Population
25
Wolf Population
20
15
Deer population
Graphing Set-up: The graph that you set-up should be similar to the one below. Remember to stay on
“TASK” when creating your graph.
10
5
1971
72
73
74
75
76
77
78
79
1980
Year
Analysis Questions: Answer the following questions in complete sentences, restating the question
within your answer.
1. Would it have been better for the ecosystem if more wolves had been introduced in 1971? Why?
2. Explain why the wolf population declined after 1975.
3. In which year was deer starvation greatest? Using the data presented and knowledge of ecology,
explain why so many deer died.
4. No deer’s died of starvation from 1977 to 1980. Why?
5. How does the size of the deer population influence the number of wolves on the island if no
hunting is allowed, what natural mechanisms will control the wolf population?
6. About how many wolves are needed to keep the deer population around 2000? Explain your
answer with information from Table 1.