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SimBio Virtual Labs®: EcoBeaker®
© 2011, SimBiotic Software for Teaching and Research, Inc. All Rights Reserved.
Isle Royale – the Moose
BE SURE TO PAUSE THE VIDEO AS YOU ANSWER EACH QUESTION,
ESPECIALLY WHEN ASKED TO MAKE PREDICTIONS.
If you were to travel on Route 61 to the farthest reaches of Minnesota and stand on the
shore of Lake Superior looking east, on a clear day you would see Isle Royale. This remote,
forested island sits isolated and uninhabited 15 miles off of the northern shore of Lake Superior,
just south of the border between Canada and the USA. If you had been standing in a similar spot
by the lake in the early 1900s, you may have witnessed a small group of hardy, pioneering
moose swimming from the mainland across open water, eventually landing on the island. These
fortunate moose arrived to find a veritable paradise, devoid of predators and full of grass, shrubs,
and trees to eat. Over the next 30 years, the moose population exploded, reaching several
thousand individuals at its peak.
 Start SimBio Virtual Labs® by double-clicking the program icon on your computer or by
selecting it from the Start Menu.
 When the program opens, select the Isle Royale lab from the EcoBeaker® suite.
Exercise 1: The Moose Arrive
In this first exercise, you will study the moose on Isle Royale. The lab simulates the arrival of the
moose that swam to the island and rapidly reproduced to form a large population.
 Click the GO button in the CONTROL PANEL at the bottom of the screen to begin the
simulation. You will see the plants on Isle Royale starting to spread, slowly filling up most of
this area of the island. Grass starts out as the most abundant plant species, but is soon replaced
with maple and balsam fir trees. The Isle Royale simulation incorporates simplified vegetation
succession to mimic the more complex succession of plant species that occurs in the real world.
After about 5 simulated years, the first moose swim over to the island from the mainland and
start munching voraciously on the plants.
 Reset the simulation by clicking the RESET button in the CONTROL PANEL. Confirm
that the simulation has been reset by checking that the TIME ELAPSED box to the right of the
CONTROL PANEL reads “0 Years”.
 Click the STEP 50 button on the CONTROL PANEL, and the simulation will run for 50
years and automatically stop. Watch the graph to confirm that the size of the moose population
changes dramatically when the moose first arrive, and then eventually stabilizes (levels out). You
can adjust how fast the simulation runs with the SPEED slider to the right of the CONTROL
 Once 50 years have passed, examine the moose population graph and answer the questions
below. (NOTE: if you can’t see the whole graph, use the scroll bar at the bottom of the graph
panel to change the field of view.)
[4.1] What is the approximate size of the stable moose population? ________ (1 pt)
[4.2] Using the horizontal and vertical axes below, roughly sketch the population size graph
showing the simulated moose population changing over time. Label one axis “POPULATION
SIZE (N)” and the other one “TIME (years)”. You do not need to worry about exact numerical
values; just try to capture the shape of the line. (2 pts)
[4.3] What is the approximate carrying capacity of moose? Draw an arrow on your graph that
indicates where the carrying capacity is (label it “K”) and then write your answer in the space
below (1 pt):
 The following logistic growth equation should look familiar (if not, revisit your notes):
[5.1] What does “dN/dt” mean, in words? (2 pts)
[5.2] Think about what happens to dN/dt in the equation above when the population size (N)
approaches the carrying capacity (K)? Think about the case when the two numbers are the same
(N = K). Rewrite the right-hand side of the equation above, substituting K for N (i.e., change the
Ns in the equation to Ks). Write this new version of the equation below (1 pt):
dN/dt = _________________ when N=K
[5.3] Look at the equation you just wrote and figure out what happens to the right-hand side of
the equation. Then complete the following sentence by circling the correct choices.
According to the logistic growth equation, when a growing population reaches its carrying
capacity (N = K),
dN/dt = 0 / 1 / K / N / r (Circle one) (1 pt),
and the population will
grow more rapidly / stop growing / shrink (Circle one) (1 pt)
 Compare your moose population growth graph to a logistic growth curve. Does the moose
population show logistic growth? Why do you say yes or no? (3 pts)
[6.1] At year 50 or later, with the moose population at its carrying capacity, what would happen
if an extra 200 moose suddenly arrived on Isle Royale? How would this change the population
graph over the next 20 to 30 years? In the space provided, draw a rough sketch of what you think
the graph would look like under these conditions. Be sure to label the axes. (3 pts)
 Now test your prediction by increasing the number of moose on the island. Click the ADD
MOOSE button in the TOOLS panel. With the ADD MOOSE button selected, move your
mouse to the ISLAND VIEW, click and hold down the mouse to draw a small rectangle. As you
draw, a number at the top of the rectangle tells you how many moose will be added. When you
release the mouse, the new moose appear inside your rectangle. Add approximately 200-300
moose. [To obtain the exact moose population size from the graph, click the graph to see the x
and y data values at any point (population size is the y value).]
 Click GO to continue running the simulation for 20 to 30 more years and watch what
happens to the moose population. Click STOP to pause the simulation. Then answer the
[8.1] Did you predict correctly in question 6.4? ________ (1 pt)
[8.2] What is the carrying capacity of moose on Isle Royale after adding 200-300 new moose?
________ (1 pt)
[8.3] Has the addition of new moose affected carrying capacity? Why or why not? (2 pt)
Exercise 2: Changes in the Weather
Recent evidence suggests that temperatures around the world are rising. In particular, the
average yearly temperature in northern temperate regions is expected to increase significantly.
This change will lead to longer, warmer spring and summer seasons in places like Isle Royale.
The duration of the growing season for plants will therefore be extended, resulting in more plant
food for moose living on the island. How would a longer growing season affect the moose
population on Isle Royale? Would it be relatively unaffected? Would the number of moose
increase indefinitely with higher and higher temperatures, and longer and longer growing
seasons? One way ecologists make predictions about the impacts of global warming is by testing
different scenarios using computer models similar to the one you’ve been using in this lab. Even
though simulation models are simplifications of the real world, they can be very useful for
investigating how things might change in the future. In this exercise, you will use the Isle Royale
simulation to investigate how changes in average yearly temperature due to global warming may
affect the moose population on the island.
 Use the SELECT AN EXERCISE menu to launch “Changes in the Weather”.
 Click STEP 50 to advance the simulation 50 years. You can zoom in to view the action up
close. The moose population should level out before the simulation stops.
 Advance the simulation 150 more years by clicking STEP 50 three times. Watch the action.
The simulation should stop at Year 200.
 Estimate the carrying capacity of the moose population. ______________ (1 pt)
 In the PARAMETERS panel below the ISLAND VIEW you will see “Duration of Growing
Season” options where you can select different scenarios. The default is Normal, which serves
as your baseline – this is the option you have been using thus far.
- The Short option simulates a decrease in the average annual temperature on Isle Royale. The
growing season is shorter than the baseline scenario, which results in annual plant productivity
that is about half that of Normal.
- The Long option simulates a warming scenario in which the growing season begins earlier in
the spring and extends later in the autumn. Plant productivity is almost double that of Normal.
[5.1] Predict how the moose population will differ with the Short growing season compared to
the Normal scenario. Will the population size be smaller or larger? Why? (2 pts)
 Without resetting the model, select the ‘Short’ growing season option. In the Short growing
season, the plant growth is half of what it was before.
 Advance the simulation another 100 years by clicking STEP 50 twice (total time elapsed
should be ~300 years).
[7.1] Estimate the new carrying capacity of the moose population. ______________ (1 pt)
 Now it’s time to consider the warming scenario.
[8.1] How do you predict the moose population will differ with a Long growing season, and
why? (2 pts)
 Without resetting the model, select the ‘Long’ growing season option from the
[9.1] Click GO and monitor the graph as the population changes.
[9.2] Click STOP and estimate the carrying capacity of the moose population under the Long
growing season scenario. ______________ (1 pt)
 Looking at your results from running the simulation under the normal climate conditions
and the two alternative scenarios, were your predictions correct? Provide biological explanations
for the trends and differences that you observed. (4 pts)