pred_prey_lab.html
9/7/10 8:08 PM
Predator Prey Simulation
Observing the relationship between predators and prey is complex.
Previously, ecologists had thought that this relationship was both simple
and direct: the predator fed on the prey thus keeping its the prey
population in check while maintaining and increasing its own
population. We now know that this relationship is not so simple and
than many other factors affect population swings in a population. In
addition, the direction of cause and effect is more subtle than it first
appears. These are some of the things to think about while doing this lab
and analyzing the data.
Our scenario takes lace in the desert of the Southwestern United States
between two native species - the Desert Cottontail rabbit (Sylvilagus
audubonii) and the Coyote (Canis vulgaris).
Instructions for the Simulation
the round beads represent the prey. In this case the beads represent rabbits. Your small
bowl should have about 100 "rabbits" that you should transfer to the beaker before you
begin.
the plastic spoons represent the predators. Our predators today will be coyotes.
the small bowl will represent the habitat in which the rabbits and coyotes will encounter
each other.
to get the lab going; place 10 "rabbits" in the bowl. The ten rabbits will represent the
initial population for the first generation. Each new generation will always begin with at
least ten rabbits; either through reproduction or by migration. (in other words, there will
always be 10 beads in the bowl at the start of each generation)
now take the plastic spoon and without looking directly into the bowl, sweep it through
the bottom of the bowl in an attempt to catch rabbits. You have to catch five or more
rabbits to survive. If that predator does not catch at least five rabbits then it is dead. If
there is only one predator and it dies; then we will assume that a new predator will
wander into the habitat for the next generation.
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if the predator captures five rabbits then it will survive and produce one offspring. (one
offspring is produced for each five rabbits captured) For example, if one coyote captures
13 rabbits, she will survive plus she will produce two offspring. If another coyote captures
15 prey, she will survive plus produce three offspring. All of the surviving coyotes plus
their offspring will be hunters in the next generation.
if a rabbit survives; it reproduces and we will assume will produce one offspring.
remove the prey from the habitat as the predators capture and eat them. Once the coyotes
are finished hunting; subtract the dead prey from the amount that you started the
generation with to figure out how many prey survived. For the next generation, double the
amount of prey and put that number at the top of the next column.
the number of rabbits in the habitat can never exceed 100. In other words, 100 is the
carrying capacity of this habitat for rabbits.
complete 20 generations of hunting; making sure to carefully record your data. Once you
are finished hunting; it is time to plot your data and complete your predator prey graph.
When graphing, use once color for the prey and a different color for the predators. You
will have two different scales for the predators and the prey.
When you graph; make sure to use graph paper.
you will have two different scales for your vertical axis. The scale for the predators will be
from 0-15; and the scale for the prey will be 0-100.
GRAPH THE ENDING NUMBER FOR BOTH PREDATORS AND PREY
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20
# of predators at
beginning
# of predators at
end
# of prey at
beginning
# of prey at end
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