Each round of this game has three steps:
Step 1: Predators hunt their prey, and data from the hunt is collected
Step 2: Predator groups are adjusted for size, representing the relative success of each predator type
Step 3: Prey groups are adjusted for size, representing the relative survival rate of each prey type
Each one-minute round of play represents one reproductive generation for both predators and prey. After the first round, calculations are done, adjustments made, and subsequent rounds are played. Ideally, participants should play at least three rounds before examining the final results.
Let the Hunt Begin!
Begin with predators gathered, standing with their backs to the habitat. The designated Timer then spreads the initial 400 prey beans randomly around the habitat, and then calls "GO!"
Predators turn around, enter the territory, and collect as many prey as possible—while following the rules. After one minute, the Timer calls "STOP!" All predators stop hunting and participants gather with their group outside the habitat. If any predator is caught violating the rules, they and the beans they have captured are eliminated from the group.
Collect Data and Adjust Group Sizes for Each Additional Generation
Step 1: Gather data for each group: Have members tally the number of captures for each type of bean, and add them together. For example, if the five members of the Hand Group captured 10, 8, 4, 7, and 3 red prey, respectively, their group captured 32 red prey in total.
Record data for each group in the Generation 1 table, filling in the rest of the chart as indicated. When all data are recorded, add together the total number of prey captured by all groups and divide by the number of groups to calculate the average number of prey captured.
Step 2: Adjust for the number of predators surviving: Before playing the next round (Generation 2), use the average number of prey captured to adjust group sizes—a change that represents the relative success of each kind of predator.
Groups that captured more than the average number of prey gain a member; those that captured fewer than the average number of prey lose a member. For example, if the Chopsticks Group captures fewer than the average number of prey, and the Hand Group captures more than the average number of prey, one member of the Chopsticks Group is transformed into a member of the Hand Group for the next round.
Step 3: Adjust for the number of prey surviving: Likewise, use the data generated to adjust the size of the prey groups to represent the survival rate of each type.
Find the number of each prey type remaining in the habitat at the end of the round. Since each type of prey (color of bean) started with 100 individuals, the number remaining for the first round will be the original 100, minus the total number of prey type captured. For example, if all predators together captured a total of 11 black-bean prey, there would be 89 remaining.
Assume that each remaining prey member will reproduce one individual. So—for this example—we would count out an additional 89 black beans and put them in the bowl. Repeat this process for each of the remaining prey types.
Click here to download an example data set and calculations.
Play Subsequent Generation Rounds and Evaluate Results
Complete as many rounds as time allows—ideally, three generations or more. Be sure to adjust the predator and prey numbers after each generation, and spread the additional prey beans randomly around the habitat before the start of each new round of “hunting.”
When you’re done, examine the results. Do you see any trends in population numbers? What explanation(s) might account for these trends? Did any of the types of predator or prey go “extinct”? Why?