Predation Simulation
AP Environmental Science
Name ___________________________Per_____
Introduction
Predator-prey interactions in a population are usually a feedback system. The prey population has a
positive effect on the predator numbers, while the predator population has a negative effect on the prey
numbers. As the prey population rises, the predator population also rises. But as the predator numbers
reach a particular value, the prey population starts to decrease, followed by a decrease in the predator
population as well. In time the predator population becomes small enough for the prey numbers to rebound
and the process continues. In nature, the fluctuations of predator and prey populations are the result of
many additional factors that affect populations in the wild. In this simulation, the factors affecting
populations are confined to the pressures of predator and prey.
Procedures
To generate data for this simulation you will consider the predator and prey to be coyotes and mice.
Remember, the numbers of predators and prey fluctuate dependent on one another. Their corresponding
numbers will rise and fall in some pattern.
1. Create a “field” on your tables that is 50 cm square.
2. Create guidelines for the simulation by determining the following:
 number of mice in the field under initial conditions (10-20): __________
 minimum number of mice a coyote needs to eat to survive and reproduce (1-5): __________
 number mice a coyote needs to eat above the minimum to produce 2 or more pups for the next
generation (>1) : __________
3. Obtain approximately 300 mice and 15 coyotes.
4. Randomly place (drop) the initial number of mice in the field.
5. Drop one preying coyote into the field. For the coyote to survive and reproduce, it must fall directly on
the number of mice determine by your guidelines (see step 2). Take the number of mice that were
“eaten” out of the field. This ends one generation.
6. Assume that the remaining mice get to reproduce by doubling their number for the next generation. If
the coyote lands on the necessary number of mice it too gets to reproduce – add one or more offspring
to begin the next generation.
7. Record the number of mice and coyotes at the beginning of each generation in Data Table 1.
Note: If all of the mice are eaten, start with the same number of mice from the first round. If none of the
coyotes survive, start again with one coyote.
8. To begin the next generation, place the new number of mice in the field. Use the new number of coyotes
to prey on the mice.
9. Repeat this for at least 7 generations to see if a pattern is developing. If your data does not seem to
reflect the predicted predator-prey pattern, then rethink and reestablish the guidelines you established
in step 2.
 number of mice in the field under initial conditions: __________
 minimum number of mice a coyote needs to eat to survive and reproduce: __________
 number mice a coyote needs to eat above the minimum to produce 2 or more pups for the next
generation: __________
10. When your data seems to be reflecting the predicted predator-prey pattern, complete 15 generations
and graph the data.
Graph
Graph the data for both mice and coyotes for 15 generations so that the interrelationship can be easily
observed. Use two y-axes, one on the left and one on the right of the x-axis. The y-axis on the left should
reflect the number of mice and the one on the right should reflect the number of coyotes. The x-axis should
reflect the generations. Use different colors to represent mice and coyotes.
Analysis and Conclusion
1. What do you predict would happen to your results if some unforeseen outside force disturbed your
system?
 What would happen if some coyotes died of disease or were driven off by larger predators or hit by
cars?
 What would happen to the prey populations in the event of a fire or if additional predators of
another species moved in?

Why would it matter at which point in the simulation such disturbances occurred?
2. Compare your graphed data to other students in class.
 Which parameters generally made the most difference in the results.

How could the initial parameters be changed to better simulate a natural system.
3. What other variables affect the number of predators and prey in a population? Describe at least four
other factors.
4. Describe at least three predator adaptations that make hunting easier. Articulate three adaptations of
prey that help them escape predation.
5. Read the handout Wolf and Moose Interactions. What type of population change did we model in this
simulation?
6. Did the simulation model top-down or bottom-up population control? Do you believe this is accurate?
Explain.
7. In your opinion, what is the best way to deal with the issue of deer overpopulation in Marin County?
Data Table 1. Predator-Prey Data
Generation Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Mice (starting number)
Coyotes (starting number)
16
17
18
19
20
21
22
23
24
25