Reg Biology
Name ______________________________ Period ______ Date __________
Deer: Predation or Starvation?
In 1970, the deer population of an island forest reserve about 518 square kilometers in
size was about 2,000 animals. Although the island had 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 while, at the same time,
increasing the quality of the herd. In 1971, 10 wolves were flown into the island. The results of the natural
predator program are presented in Table 1.
Table 1: Natural Predator Program Results
Year
1971
Wolf
Population
10
Deer
Population
2000
Deer
Offspring
800
Predation
400
Starvation
100
Population
Change
300
1972
12
2300
920
480
240
200
1973
16
2500
1000
640
500
-140
1974
22
2360
944
880
180
-116
1975
28
2244
996
1120
26
-150
1976
24
2094
836
960
2
-126
1977
21
1968
788
840
0
-52
1978
18
1916
766
720
0
46
1979
19
1962
780
760
0
20
1980
19
1982
790
760
0
30
Analysis:
1. Define limiting factor (I 16.2)
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2. Is wolf predation a density-independent or density-dependent factor? (circle one) Explain your
choice below. (I 16.2)
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3. List 3 factors other than predation or starvation, that limit a deer population, and identify each as
either density-dependent or density-independent. (I 16.2)
1._______________________________________________
2._______________________________________________
3._______________________________________________
4. In what year was deer starvation the greatest? _____ Why do you think that deer starvation was so
high in this particular year? (I 20.1)
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5. How many deer died due to predation in 1980?_____ (I 20.1)
How many wolves were on the island in 1980?_____ (I 20.1)
What was the average number of deer taken by each wolf in that year?_____(show work below)
6. How would the ecosystem most likely have been affected if more wolves had been introduced in
1971? (circle one) (E 20.1)
a. The number of deer offspring would decrease.
b. The number of deer lost to predation would increase.
c. The number of deer lost to starvation would decrease.
d. The total number of deer would stay the same.
Explain your reasoning:
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7. Finally, plot the fluctuation in the deer and wolf population on graph paper for the ten-year study.
This graph will need one x-axis and two y-axes. Include a title, labeled axes and proper scale. (I 20.3)