Grade Level/Subject
9-Biology
Unit
Ecology
Enduring Understanding

As any population of organisms grows, it is held in
check by interactions among a variety of biotic and
abiotic factors.
SOL Objectives
Bio 8a
Title
Exploring Ecology through Predator Prey Modeling
Lesson Objective
Student will study the relationship between the sizes of
the predator and prey populations and the effects of
various factors on the dynamics of an owl/mousepredator/prey model.
Inquiry Level
3
Materials Required
Pencil, paper, scissors, tape, graph paper, other materials
as needed for part two to be determined by student design
Inquiry Lab
Exploring Ecology through Predator Prey Modeling
Purpose:
Student will study the relationship between the sizes of the predator and prey populations
and the effects of various factors on the dynamics of an owl/mouse-predator/prey model.
This lab will be run in two parts. The first establishes a baseline relationship between an
owl predator population and its mouse prey population.
In the second parts of this lab, students will brainstorm what factors can be altered in the
model, hypothesize what effects these alterations may have on the two populations, then
test those hypotheses.
Part I
Baseline lab:
MATERIALS
Per team of 2: Tape, Meter Stick, and Scissors
INTRODUCTION
Animals spend much of their time looking for and consuming food. Some eat plants,
some eat meat and some eat both. Many meat-eating animals obtain their meat by hunting
other animals. The hunters are known as predators and the hunted animals are known as
prey.
In this lab you will do a simulation of a predator/prey relationship, with owls as predators
and mice as prey. In nature, owls and mice are often found living in forests. The forest in
your simulation will be Hoot Woods.
Owls are excellent hunters. The various kinds of owls eat many different kinds of
animals, including rabbits, squirrels, rats, mice, shrews, birds, fish, and insects. To
simplify the simulation, you will limit the owl’s food supply to mice.
PROCEDURE
Each team should cut out the 300 mice squares and 1 owl rectangle. Fold the rectangle in
thirds to make an owl square about 6 cm on a side. Tape the triangle to hold the shape.
Each team should mark off a square approximately 50 cm on a side on their table. This
square represents Hoot Woods, where the mice and owls live.
You will simulate 25 generations of owls and mice. The mice can be eaten and the owls
can starve. Surviving mice and owls can reproduce. To make calculations easier, each
surviving mouse and owl will be considered capable of producing one offspring.
In each generation, the surviving mouse population will double to form the next
generation. For example, if six mice are living in the woods and two are caught by an
owl, then four mice will survive. These four mice will each produce one offspring, and
the next generation will begin with eight mice. Remember, the number of offspring is
always the same number as the number of surviving mice. At any one time, the maximum
mouse capacity of Hoot Woods is 300 mice.
In order to survive, each owl must catch at least three mice in every generation. If an owl
does not catch three mice, it will starve. For each three mice that an owl catches, it
produces one offspring. For example, if an owl catches eight mice it will reproduce two
new owls, making a total of three owls to begin the next generation.
At the beginning of each generation, there must be at least three mice and one owl in the
woods. If the populations drop below these numbers (by being eaten or starving), new
mice and owls will migrate in. For example, if just one mouse survives the first
generation, just one offspring will be produced, for a total of two mice. One mouse must
migrate in to bring the mouse total to three. If all owls die, one owl must migrate in.
A. HOOT WOODS SIMULATION
The simulation is played as follows. Place the mouse squares at random in Hoot Woods.
Then from a height of about 30 cm, drop the owl square into the woods. Try to hit as
many mice as you can in one drop. When an owl square fully or partly covers a mouse
square(s), that is a “catch”. If there is more than one owl in a generation, drop the owl
square once for each owl.
Remove and count the number of mice caught by each owl (at each drop). Keep all the
mice from each owl in separate stacks. Record the data on the chart. You might want to
have one team member make the catches while the other records the data.
For example, suppose generation 3 begins with 20 mice and 2 owls. You make a drop for
the first owl and catch 7 mice. On the second drop, the second owl catches only 2 mice.
The owls have caught a total of 9 mice. There are 11 mice left in Hoot Woods, and they
reproduce 11 mice. The next generation will start with 22 mice. Because the first owl
caught 7 mice, it reproduces 2 offspring for the next generation. The second owl only
caught 2 mice; it starves and does not survive.
The data chart for this example would look like this:
NumberNumberNumberNumberNumber
Generation of
of
of
of
of
Number of
Mice at Owls at Mice
Start Start Caught Owls Surviving Surviving
*
**
Starved Mice + Owls +
Offspring Offspring
3
20
2
9
1 11+11=22 1+2=3
4
22
3
Number Number Number Number Number Number
of
of
of
of
of
of
Mice at Owls at Mice
Start
Start Caught Owls Surviving Surviving
* **
Starved Mice + Owls +
Generation
Offspring Offspring
1
3 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
*There always must be at least three mice at the start; if necessary, have mice migrate in.
**There always must be at least one owl at the start; if necessary have one owl migrate
in.
Now, gather the data for 25 generations. Remember to remove the caught mice and
starved owls, and to add the offspring mice and owls. Always place randomly in the
woods.
B. GRAPHING DATA
When you have finished gathering data, plot your data on population size on the graph
provided. Use Xs for the owl data and dots for the mouse data. Design the Y-axis so that
most of the graph is used.
Connect the data points of each population using different lines. Your graph should have
two distinct lines: one for the owl population and one for the mouse population.
Owl and Mouse Populations in Hoot Woods
I
I
n italIuoI Namsma ervImNI uo rebmuN
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Generation Number
On this page are 100 mice and the owl. On the next page are the remaining 200 mice.
ANALYSIS
Complete these questions after the baseline lab.
1. Which population first increases in size?
2. Describe the pattern of the fluctuations in the sizes of the two populations.
3. By looking only at the graph, can you tell which species is the prey and which is the
predator?
How can you tell?
4. Which species attains the greater number of individuals? Why?
5. What do you think would happen to the mouse population in Hoot Woods if the owls
were all hunted to extinction? Why?
Part II
In your lab groups come up with a factor you wish to change about the simulation to
make it either more realistic, more interesting, or cycle differently than it did in the first
simulation. Take a few minutes as a group to come up with as many ideas as you can.
Think about how you could change the model to show the change in the factor.
Teacher tip:
It’s best if the students work in small groups on ideas first and come up with as many as
possible then share out as a class and put all ideas on the board for discussion. From
those the best ones can be selected for experimentation.
Some possible ideas may be….
Various range sizes
Altering mouse regeneration rate
Altering owl regeneration rate
Prey value (size)
Predation rate (predator size)
Multiple predators governed by different rules.
A predator that preys on the owls
A disease
Safe cover zones (Camouflage)
Weather (turn a fan on)
Student will then design a way to alter that factor in the model and rerun the simulation
with the new rule (alteration to the model) and find what effect it has in the two
populations.
Before the second simulation answer these questions
1. What factor in the simulation is your group going to alter?
2. How will you model that alteration in the simulation?
3. What is your hypothesized effect of this alteration on the baseline data?
Data table and Graph for part II
NumberNumberNumberNumberNumber Number
of
of
of
of
of
of
Mice at Owls at Mice
Start Start Caught Owls SurvivingSurviving
* **
Starved Mice + Owls +
Generation
Offspring Offspring
1
3 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
After the second simulation
1. What was the effect of your alteration?
2. Did this effect match your hypothesis? EXPLAIN
3. How could you improve your procedures to better simulate the factor you were
exploring?
4. Share your findings with the class and get feed back on your procedures. Take notes on
their finding in the space below and help them critique their procedures. Be clear and
concise.