Predator-Prey Simulation (paper/card model)
Idea adapted from http://www.biologycorner .com/worksheets/predatotsim.html
This practical enables students to model predator prey interactions by recording the numbers of predators and prey in a model
ecosystem consisting of paper or card squares or beans or many other readily available materials. Students should be able to see
the dramatic build up of the prey numbers with the predator numbers lagging behind them, taking both populations above their
carrying capacity. Then the populations can be seen to decline again, as density dependent factors produce negative feedback
mechanisms which take both populations back below the equilibrium point again.
Method:
Use scrap paper and get students to cut up paper to make their own predators and prey – they can use large squares for predators
and small for prey, with their own adaptations if you want to make it more open ended, so that it can pick up more assessment
criteria.
Or if you prefer:
Prepare in advance (per group) :
1. Approximately 200 beans to represent the prey population
2. 50 large squares cut from card - the large squares represent the predator population
You may choose to give each student a preprinted data table (last page) or ask them to construct their own. Graph paper is needed
to process results, unless a spreadsheet is to be used.
Model Ecosystem: Predator-Prey Relationships
Instructions:
The table represents the ecosystem
1. Place 3 beans (to represent “prey” colonizing an ecosystem), on the table.
2. Toss 1 predator “note card” onto the table and attempt to make the card touch as many “prey” as possible. In
order to survive, the predator must capture at least 3 prey. It will be impossible for your predator to survive at
this point.
3. Remove any “prey” captured and record your data for the 1st generation.
4. One rule to use is that the “prey” population always doubles each generation. Count how many prey you
have left on your table, double that number and add prey beans to the table. Record the number in the data
table under the 2nd generation “number of prey”. (It should be 2x the number you have under the “prey
remaining” for generation 1)
5. The predator inevitably died during the first round, but a new predator moves in for the second round, so
record 1 in the “number of predators” for generation 2 to represent the new arrival. Repeat the tossing
procedure and record data for the second generation.
6. Again, number of prey doubles, but if your predator didn’t “capture” 3 prey, it died. A new predator always
moves in for the next round. Keep going, adding to the number of prey each round according to the rules of
the system.
7. Eventually your predator will be able to capture enough prey to survive. At this point it survives and
reproduces. Add to your predator population by adding an extra predator for each predator survivor. Now when
you toss your predators, you will be tossing more than one. Don’t forget to remove any “captured” prey.
8. Continue to record the data through about 20 generations.
Conclusion Questions:
1. Construct a graph with generations 1 through 20, on the x-axis. On the Y-axis, you will plot the population
numbers for each generation (number of predators, number of prey). Plot both populations on the same axes,
using different lines.
2. Describe and analyze your results, comparing them with the population theory you have learned.
3. Evaluate your model, suggesting improvements to the model so that it would better simulate how predator
and prey interact.
4. What type of feedback is shown from the results on your graph (negative or positive)? How do you know?
5. Based on your results, is predation density dependent or density independent? Why did you come to this
conclusion?
6. What type of reproductive strategy do you think the prey “beans” have? Why?
7. What type of reproductive strategy do you think the predator “note cards” have? Why?
8. When the natural disaster came and killed off half of your prey population, was this density dependent or
density independent? Why did it kill only the prey population?
Name_______________________________Date________________________Block_____
Generations
1st
Number of
Predators at
beginning of
generation
Number of
Prey at
beginning of
generation
Number of
Predators
remaining at
end of
generation
Number of
Prey
remaining at
end of
generation
2nd
3rd
4th
5th
6th
7th
8th
9th
10th
11th
12th
13th
14th
15th
16th
17th
18th
19th
20th