Isle Royale Population Activity
As you have read, Isle Royale has a unique community of wolves and moose. Since the island is
fairly distant from the mainland, the communities on the island are not affected by migration
(although the animals had to have gotten there somehow…probably by waking across ice).
Population dynamics within an ecosystem can vary, especially as regards predator-prey
relationships. Because of this, graphs showing the population sizes of two interacting groups are
frequently shown on the same figure in order to illustrate the cyclical nature of their relationship.
As you can see from your textbook (see Infographics 21.5, 21.6), a population spike in the prey
animal will often be followed by a population spike in the predator. This happens because when
the prey population is high, the predator population has more food. Food provides the energy
necessary to survive and reproduce. When there is not enough food available, an animal will not
be able to spare the energy to reproduce - and the population will either stay the same or decline.
Isle Royale Population Simulation
Materials:
1. A pair of dice. If you do not have an actual die or dice, you can go to http://www.rolldice-online.com/ for simulated dice.
2. You can keep track of your population numbers using the spreadsheet that goes along
with this activity, but you might find it useful to have physical objects (forks and spoons?
Paperclips and thumbtacks?) to represent your populations of wolves and moose.
Directions:
1. Open the Excel file “Isle Royale Population Simulation Worksheet.xls”
2. Start with 6 “moose” and 2 “wolves” on the island.
3. For each round, figure out your wolf hunting success: for each wolf you have, roll both
dice (so to start, you will roll both dice once for the 1st wolf and then both dice again for
the 2nd wolf). For each die, if it lands on a 4, 5 or 6, the wolf has caught a moose. If the
wolf caught 0 moose (both dice unsuccessful), then the wolf dies. If the wolf caught 1
moose (one die has 4,5 or 6, the other die unsuccessful), then the wolf lives. If the wolf
caught 2 moose (both dice show 4, 5, or 6), then the wolf reproduces and 1 additional
wolf is added to the board.
a. If the first wolves to hunt successfully catch all of the moose out of your
population, then any additional wolves will not be able to catch any moose, so
they will die. Similarly, if you’re down to one moose in your population, even if
a wolf rolls two successful dice, they can only catch that one moose. This is
where it helps to have some kind of markers to keep track of your populations!
4. For each round, figure out your moose population: Each round, subtract the number of
moose killed by the wolves in that round, then add 3 moose to the moose population to
simulate moose reproduction.
5. After each round, record the total number of moose and wolves on the Excel spreadsheet.
6. Play the game for 20 rounds. If your wolves decline to 0, start the next round with 1 wolf.
If your moose decline to 0, start the next round with 3 moose.
When all 20 rounds are complete and your data has been entered in the excel file, take a look at
the chart that was generated as you added your data, and answer the questions in the assignment.
Post the excel file with your graphed data as part of your submission for this assignment.
Note: This activity does not actually depict the population of the moose or wolves living on Isle
Royale in the past, present or future. Results will vary!
Example:
Starting with 2 wolves and 6 moose.
Round 1:
Wolf 1 – Catches two moose, survives and reproduces.
Wolf 2 – Catches one moose, survives but does not reproduce.
Total Wolf Population at the end of Round 1 = 2 wolves at start of round + 1 reproduced
wolves – 0 dead wolves = 3 wolves
Total Moose Population at the end of Round 1 = 6 moose at start of round – 3 moose
caught by wolves + 3 reproduced moose = 6 moose
Round 2:
Wolf 1 – Catches no moose, dies.
Wolf 2 – Catches one moose, survives but does not reproduce.
Wolf 3 – Catches one moose, survives but does not reproduce.
Total Wolf Population at the end of Round 2 = 3 wolves at start of round + 0 reproduced
wolves – 1 dead wolves = 2 wolves
Total Moose Population at the end of Round 2 = 6 moose at start of round – 2 moose
caught by wolves + 3 reproduced moose = 7 moose