Rabbits and Wolves

What is Rabbits and Wolves?

This applet allows the user to simulate how nature keeps its balance. This applet shows how wolves and rabbits would behave in their natural setting. The general rules of this applet are:

• 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).
• A rabbit cannot reproduce if there is a wolf around her.
• Rabbits and wolves can only move up, down, left, or right 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
• A rabbit gives a food value of 10 to the wolf that eats it.

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.

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How Do I Use This Activity?

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.

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 applet 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 numbers 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 percentage of the area filled by rabbits, wolves, and grass 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, such as reproduction rates and maximum lifespans.
• The View Simulation Key button opens a window that displays a legend for the grid.
• The Seed Random Number Generator button opens a window that allows you to set a two-character random seed, which will determine the initial placement of the rabbits and wolves. This will allow you to conduct a series of experiments where the initial parameters are controlled. Since rabbits and wolves move, reproduce, and die based on set probability, each simulation will have different results, even if none of the parameters are changed. Note that once the seed has been set, the only way to go back to random placement is to reload the page using your browser's refresh button.