Predators, Prey, Limiting Factors, and Carrying Capacity
In 1970 the deer population of an island forest reserve about 518 square kilometers in size was about 2000 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 natural predation would keep the deer population from becoming too large and also increase the deer quality (or health), as predators often eliminate the weaker members of the herd. In 1971, ten wolves were flown into the island.
- Make a Hypothesis
Predict how the deer population will change over the years.
Results:
Data TableTrials (years) / 1971 / 1972 / 1973 / 1974 / 1975 / 1976 / 1977 / 1978 / 1979 / 1980
Number of Deer / 2,000 / 2,300 / 2,500 / 2,360 / 2,224 / 2,094 / 1,968 / 1,916 / 1,952 / 1,972
Number of Wolves / 10 / 12 / 16 / 22 / 28 / 24 / 21 / 18 / 19 / 19
- Graph the deer and wolf populations on the graph below in a graph line. Use one color to show deer populations and another color to show wolf populations.
C. Conclusion
Compare your hypothesis to your graph. How did the deer and wolf populations change over time?
D. Discussion
1. Once the wolves were introduced, what is the carrying capacity for deer and wolves in the ecosystem?
2. What do you think would have happened to the deer on the island had wolves NOT been introduced?
3. What limiting factors affect deer population?
4. What limiting factors affect wolf population?
5. How would you describe the relationship between a deer and wolf population sharing an ecosystem? What patterns do you see in both populations?
- Would you agree or disagree with the following statement. “Predators and prey populations exist in a balance” Explain.
- In summary, what are the advantages of having a population of predators and preys in an ecosystem?