Rabbits and Wolves Exploration
Predator – Prey Simulation Activity
http://www.shodor.org/interactivate/activities/rabbits/index.html
Questions
In this applet allows the user to simulate how nature keeps its balance. Experiment with the settings in the Rabbits
and Wolves Activity to achieve sustainable populations.
Rabbits and Wolves Help
This activity allows the user to see how wolves and rabbits would behave in their natural setting as an example of
how nature keeps its balance. This Java applet requires a Java-capable browser. If you don’t see the applet Java, it
may not be functional in your browser or on your machine.
Controls and Output
The Start Simulation button on the top-left of the applet begins animating the interactions between the different
elements (rabbits, wolves, and the grass) of the grid. It becomes the Pause Simulation button when pressed. There is
also a Step Simulation button in the top-center of the applet that allows you to see the simulation step by step.
The Pause Simulation button allows you to pause the simulation and look at the current state of the grid. It becomes
the Resume Simulation button when pressed.
The Resume Simulation button allows you to resume the simulation after it has been paused. It becomes the Pause
Simulation button when pressed.
The Reset Simulation button sets up a new simulation based on the current parameters.
The Forest Size menu allows you to select the size of the forest.
The Speed scroll bar allows you to speed up and slow down the rate at which the applets displays the simulation.
The Forest Border menu allows you to choose between toroid and island. Toroid allows the rabbits to move off the
screen on one edge and wind up on the opposite edge of the forest. Island does not allow them to move this way.
The View Population Graph button opens a window that displays a graph of the number of rabbits, wolves, and
grass per iteration.
In the Population Graph window there is the Display Tabular Data button that allows you to see the numbers for the
last 250 iterations.
The View Cumulative Stats button allows you to view the population statistics for the current stage of the simulation.
The View/Modify Parameters button opens a window that allows you to modify various settings of the simulation.
The View Simulation Key button opens a window that displays a legend for the grid.
Rules and Default Parameters
Two rabbits cannot occupy the same section of grass.
Two wolves cannot occupy the same section of grass.
Each rabbit can only eat grass when he has not reached his maximum food capacity. (The maximum food
capacity can be modified).
A wolf will not eat a rabbit if the rabbit will make him surpass his maximum food capacity. (The maximum
food capacity can be modified).
Rabbits and wolves can only reproduce when they reach a certain age and have a sufficient amount of food.
(The age of reproduction and amount of food required to reproduce can be modified).
Rabbits and wolves can move in any direction (including diagonally) one space at a time.
Rabbits and wolves die if they get too old or if there is insufficient food. (Maximum age can be modified).
The grass growth rate is 1. (This growth rate can be modified).
The rules for the births and deaths of rabbits and wolves are a bit more detailed. Let’s begin with rabbits which have
the following (adjustable) default parameters:
Maximum food capacity: 45 units
Metabolism rate: 3 units/stage
Reproduction age: 10 stages
Probability of reproduction in a suitable environment: 50%
Minimum food requirement to reproduce: 40 units
Maximum age: 25 stages
Rabbits give a food value of 10 to the wolves when eaten.
Using this information, along with the general rules, the computer will determine whether each rabbit will
live, die, or reproduce during each stage.
Wolves have the following (adjustable) default parameters:
Maximum food capacity: 200 units
Metabolism rate: 2 units/stage
Reproduction age: 10 stages
Probability of reproduction in a suitable environment: 50%
Minimum food requirement to reproduce: 120 units
Maximum age: 50 stages
Using this information, along with the general rules, the computer will determine whether each wolf will live, die, or
reproduce at each stage.
APES Investigations Procedures
A.
1.
2.
3.
4.
Default Simulation
Select “View Population Graph” and drag it to the right side to maintain access to all the buttons.
Select “Start Simulation.”
Stop the simulation after extinctions make it pointless.
Record the number of peaks for each species & the stage at which any species went extinct.
B.
1.
2.
3.
4.
5.
6.
7.
8.
Controlled Experiments - Change only 1
Select “View/Modify Parameters.”
Choose "View/Modify Rabbit Parameters" or "View/Modify Wolf Parameters."
Change & record ONE & ONLY ONE parameter of your choice.
Close the parameter window so that only the Population Graphs & Forest chart are visible.
Start Simulation.
Stop simulation after extinctions make it pointless.
Record the number of peaks for each species & the stage at which any species went extinct.
Repeat 1-7 for each trial until you achieve a sustainable system with no extinctions.
C. Analysis
For each trial describe what difference the change made to the results.
Rabbits and Wolves Exploration
Predator – Prey Simulation Data Table
Trial
Rabbits
Maximum food
capacity:
Metabolism rate:
Reproduction age:
Probability of
reproduction in a
suitable
environment:
Minimum food
requirement to
reproduce:
Maximum age:
Rabbit food value to
the wolves when
eaten.
Wolves
Maximum food
capacity:
Metabolism rate:
Default
20
45 units
3
units/stage
10 stages
50%
40 units
25 stages
10
200 units
2
units/stage
10 stages
50%
Reproduction age:
Probability of
reproduction in a
suitable
environment:
120 units
Minimum food
requirement to
reproduce:
50 stages
Maximum age:
Forest Size
Grass Peaks
Rabbit Peaks
Wolf Peaks
Grass Extinction
Stage
Rabbit Extinction
Stage
Wolf Extinction
Stage
Medium
1
2
3
4
5
6
7
8
9
C. Analysis
For each trial describe what difference the change made to the results.
1.
2.
3.
4.
5.
6.
7.
8.
9.