Survival is a Roll of the Dice:
A simulation to model the how a wolf pack will survive with
and without human interference
Name: ______________________________
Per ______ Date ________
The History
Although wolf packs once roamed from the Arctic tundra to Mexico, loss of habitat and extermination programs
led to their demise throughout most of the United States by early in the 1900s. In 1973, the US Fish and Wildlife
Service listed the northern Rocky Mountain wolf (Canis lupus) as an endangered species and designated Greater
Yellowstone as one of three recovery areas. From 1995 to 1997, 41 wild wolves from Canada and northwest
Montana were released in Yellowstone National Park. As expected, wolves from the growing population
dispersed to establish territories outside the park where they are less protected from human-caused mortalities.
The park helps ensure the species’ long-term viability in Greater Yellowstone and has provided a place for
research on how wolves may affect many aspects of the ecosystem.
The Results
Preliminary data from studies indicate that
wolf recovery will likely lead to greater
biodiversity throughout the Greater
Yellowstone ecosystem. Wolves prey
primarily on elk and these carcasses have
provided food to a wide variety of other
animals, especially scavenging species.
Wolves are increasingly preying on bison,
especially in late winter. Grizzly bears have
usurped wolf kills almost at will, contrary to
predictions and observations from other
areas where the two species occur. Wolf kills,
then, provide an important resource for
bears in low food years. Aggression toward
coyotes initially decreased the number of
coyotes inside wolf territories, which may
have benefited other smaller predators,
rodents, and birds of prey.
So far, data suggests wolves are contributing
to decreased numbers of elk calves surviving
to adulthood and decreased survival of adult
elk. Wolves may also be affecting where and
how elk use the habitat. Some of these
effects were predictable, but were based on
research in relatively simple systems of one to two predator and prey species. Such is not the case in
Yellowstone, where four other large predators (black and grizzly bears, coyotes, cougars) prey on elk—and
people hunt the elk outside the park. Thus, interactions of wolves with elk and other ungulates have created a
new degree of complexity that makes it difficult to project long-term population trends.
The Outlook
The future of wolves in Greater Yellowstone will depend on how livestock depredation and hunting of wolves
outside the park are handled. Wolf populations will also continue to be affected by the availability of elk, deer,
and bison populations, which fluctuate in response to hunting quotas, winter severity, and disease. To what
extent wolves may have contributed to the decline in the northern Yellowstone elk population since the mid1990s or the possibly related resurgence of willow in some areas is an ongoing topic of debate.
Source: NPS- http://www.nps.gov/yell/learn/nature/wolfrestorationinfo.htm
Your Task: After the reintroduction of the gray wolf, populations grew and they were removed from the
removed from the endangered species list. Biologists continued to monitor the populations by tracking
individual wolves with radio transmitter collars. Without the protection of the Endangered Species Act, will the
wolves be able to survive? Your team has just spotted a pack of gray wolves. Back at camp, you develop a model
of this wolf pack’s population and use it to determine what must be done to make sure this pack survives. In the
simulation, you will predict how this pack of wolves will survive under two different conditions: without human
interference and with human interference. You will use dice to determine what happens to the wolf pack over
time.
Rules of the Simulation:
1. Start with 2 adult wolves and 3 pups to equal 5 total wolves.
2. Each roll of the dice represents the passage of 1 year. Look at the dice and check the information sheet to
see what happened to your pack during the year.
3. Fill in the information on the wolf record table and adjust the number of wolves according to what
happened to your pack.
4. Repeat 15 times to model 15 years of time.
**Every year add 3 wolves to your pack (due to reproduction and mature pups leaving the pack).
5. Construct a double line graph to show how the wolf pack population is predicted to change over 15 years.
Analyze the Data:
1. Describe what happened to the pack of wolves over the years without human interference.
2. Describe what happened to the pack of wolves over the years with human interference.
3. Did your pack have better survival rates with or without human interference? Explain your data.
Evaluate the Simulation
4. What the limitations of this simulation used to model how the wolf pack changed over time?
5. How could the simulation be improved? (be specific)
Further Analysis:
Watch the National Geographic Video Wolves of Yellowstone and answer the following:
6. What is a trophic cascade? (Describe the one depicted in the video.)
7. How did the reintroduction of wolves help humans?
Not everyone agrees on the roles wolves have played in restoring the ecosystem in Yellowstone National Park.
Read the following: http://ournationalparks.us/park_issues/reintroduction_of_wolves_brings_controversy/
8. Why were ranchers opposed to the reintroduction of the gray wolf population?
9. How has the federal government tried to appease the ranchers for reintroducing the gray wolf?
Survival is a Roll of the Dice
Information sheet
Simulation 1: Without Human Interference
What happened during
the year:
If you Roll:
You:
Double 2, 3, 4, 5
Subtract 2
Double 1
Double 6
Dice add up to 3
Divide by 2
Add 1
Subtract 1
Dice add up to 4 (not double 2)
Subtract 2
Dice add up to 5
Dice add up to 6 (not double 3)
Dice add up to 7
Make no change
Make no change
Make no change
Dice add up to 8 (not double 4)
Divide by 2
Dice adds up to 9
Dice adds up to 10
(not double 5)
Make no change
High pup mortality rate, 2 pups
die
Disease kills half the pack
Extra pup this year!
One pup dies
Two wolves die of natural
causes
Pack lives well for the year
Pack lives well for the year
Pack lives well for the year
Food shortage kills half the
pack
Pack lives well for the year
Make no change
Pack lives well for the year
Dice adds up to 11
Subtract 1
Wolf is attacked by another
wolf pack and dies
Source: WolfQuest http://www.wolfquest.org/classroom_activities.php
Dice add up to 4 (not double 2)
Survival is a Roll of the Dice
Information sheet
Simulation 2: With Human Interference
What happened during
the year:
If you Roll:
You:
Double 2, 3, 4, 5
Subtract 2
Double 1
Double 6
Dice add up to 3
Divide by 2
Add 1
Subtract 1
Dice add up to 4 (not double 2)
Subtract 2
Dice add up to 5
Dice add up to 6 (not double 3)
Dice add up to 7
Subtract 2
Make no change
Make no change
Dice add up to 8 (not double 4)
Divide by 2
Dice adds up to 9
Dice adds up to 10
(not double 5)
Subtract 2
High pup mortality rate, 2 pups
die
Disease kills half the pack
Extra pup this year!
One pup dies
Two wolves die of natural
causes
Hunter kills 2 wolves
Pack lives well for the year
Pack lives well for the year
Food shortage kills half the
pack
Human kills 2 wolves
Subtract 1
Wolf is hit by a car and dies
Dice adds up to 11
Subtract 1
Wolf is attacked by another
wolf pack and dies
Source: WolfQuest http://www.wolfquest.org/classroom_activities.php
Dice add up to 4 (not double 2)