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Soldiers displaying wolf pelt at Soda Butte Creek patrol
station, Yellowstone National Park, 1905. Credit: NPS
WOLVES OF YELLOWSTONE
Subject Area: Science
Grade Levels: 7-12
Purpose and Overview: This set of activities was
inspired by the Wolves of Yellowstone | EARTH A New
Wild video from PBS LearningMedia. The purpose of
these activities is to introduce students to the ecological
impact of wolf reintroduction, the controversy
surrounding the wolves, and finally to have students
extend their understanding and apply it to another wolf
reintroduction debate that rages on today regarding
Isle Royale National Park in Michigan.
The lesson plan is divided into four parts. In Part 1,
students will discover how the absence of wolves
impacted the Yellowstone National Park ecosystem.
They will explore the concept of a trophic cascade
through a short video clip and through an in-depth
analysis of data from scientific study conducted in the
park after wolf reintroduction in 1995.
In Part 2, students will examine the pros and cons of various scenarios that were presented by the U.S. Fish
and Wildlife Service during the 1994 decision-making process on whether or not to reintroduce wolves to
Yellowstone National Park. Through the use of role-playing, students will learn about the varied opinions
regarding wolf reintroduction and will ultimately be forced to compromise and arrive at a final proposal
based on the park needs and the public commentary.
In Part 3, students will examine research that describes how wolf reintroduction has impacted the park and
compare what we know now to the original public concern. The purpose of this activity is to allow students
to examine research to determine the actual impact of the wolves on the park twenty years later and
relate it to the initial public concerns that were expressed in the role-play activity in Part 2.
In Part 4, students will extend upon the knowledge they have gained in learning about the trophic cascade
that occurred in Yellowstone National Park (YNP) and apply it to a modern problem in Isle Royale
National Park.
Time:
Part 1: One to two 45-minute class periods
Part 2: Two to three 45-minute class periods
Part 3: Two 45-minute class periods, with homework
Part 4: One 45-minute class period plus homework
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© Janet Haas for The Nature Conservancy
Introduction
In 1872, the world’s first national park, Yellowstone, was born. However, while it protected approximately
3,472 square miles of land (2,221,766 acres), it did not protect the gray wolves that lived inside its
boundaries. In fact, in the early years of the park any visitor could hunt and kill any wild game or
predator they encountered. Wolves were especially vulnerable because they were seen as an undesirable
predatory species.
At least 136 wolves were killed in the park between 1914 and 1926. By the 1940’s wolf packs were
seldom reported in the park. In fact, by the mid-1900’s wolves had been nearly eliminated not just from
Yellowstone but from the lower 48 states entirely.
In the 1940’s a growing movement of conservationists, environmentalists, biologists, and park officials
supported reintroduction of the wolves to Yellowstone. However, it wasn’t until 1991 that Congress
directed the U.S. Fish and Wildlife Service to develop an environmental impact statement regarding wolf
reintroduction and in 1995, the park moved forward with a plan to reintroduce wolves to the area.
Reintroduction was not without controversy as there were, and still are, many stakeholders involved in the
Yellowstone area, each with unique concerns. However, in the twenty years since the reintroduction of the
wolves, scientists have noticed many positive changes to the park ecosystem. This set of activities seeks to
introduce students to the trophic cascade that has occurred in the park and the positive changes in the
ecosystem since the reintroduction of a top predator the wolf.
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Part 1: Defining Trophic Cascade
Purpose: The purpose of this activity is for students to discover how the absence of wolves impacted the
Yellowstone National Park ecosystem. Students will explore the concepts of a trophic cascade through a
short video clip and through an in-depth analysis of data from scientific study conducted in the park after
wolf reintroduction in 1995.
Time: One to two 45-minute class periods
Materials:
Internet, computer, LCD projector
Copies of student worksheet for Part 1
URL: http://www.pbslearningmedia.org/resource/8c4af2f8-f017-41ed-b2ca-
ec7f94729d93/wolves-of-yellowstone-part-1-student-worksheet/
Wolves of Yellowstone | EARTH A New Wild Video
URL: http://www.pbslearningmedia.org/resource/a58e3ca2-52ab-45f5-87ac-
26ee0d681146/wolves-of-yellowstone-earth-a-new-wild/ (can be downloaded)
Objectives:
The student will
Describe the conditions of the Yellowstone National Park (YNP) ecosystem in the absence of
wolves.
Explain the trophic cascade that occurred in YNP.
Predict what would happen to YNP if environmental conditions changed.
Examine and analyze data on the wolf, elk, and plant populations in YNP and describe how the
populations are interdependent.
Analyze the change in resource availability in YNP and construct an explanation of the subsequent
changes in animal populations.
Next Generation Science Standards:
Disciplinary Core Ideas:
LS2.A: Interdependent Relationships in Ecosystems
LS2.C: Ecosystem Dynamics, Functioning, and Resilience
Crosscutting Concepts:
Patterns
Cause and Effect
Stability and Change
Science and Engineering Practices:
Analyzing and interpreting data
Constructing explanations
Engaging in argument from evidence
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Performance Expectations:
Middle School
MS-LS2-1. Analyze and interpret data to provide evidence for the effects of resource availability on
organisms and populations of organisms in an ecosystem.
MS-LS2-2. Construct an explanation that predicts patterns of interactions among organisms across multiple
ecosystems.
MS-LS2-4. Construct an argument supported by empirical evidence that changes to physical or biological
components of an ecosystem affect populations.
High School
HS-LS2-6. Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain
relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result
in a new ecosystem.
HS-LS4-5. Evaluate the evidence supporting claims that changes in environmental conditions may result in: (1)
increases in the number of individuals of some species, (2) the emergence of new species over time, and (3)
the extinction of other species.
Vocabulary:
Apex predator: a top-level predator with no natural predator of their own; resides at the top of a food
chain.
Browser: an organism that eats the shoots, leaves, and twigs of trees or shrubs; elk are browsers (and
grazers).
Browsing: the act of eating shoots, leaves, and twigs of trees or shrub.
Cottonwood recruitment: the growth of seedlings or sprouts above the level of browsers. In other words,
the trees are able to grow taller than the level at which elk and other browsers can eat them.
Grazer: an organism that feeds on grass; elk are grazers (and browsers).
Habitat: the home or environment of a plant, animal, or other organism.
Keystone species: a species that has a disproportionately large effect on its environment compared to its
relative abundance. When a keystone species is removed from a system, the ecosystem may change
drastically, even if the species removed was a small part of the entire ecosystem.
Trophic cascade: a trophic cascade occurs when the impact of a predator on its prey affects one or more
feeding or trophic level. Predators control the populations of their prey and thus indirectly benefit and
increase the abundance of their prey’s prey. When the apex predator is removed, the lack of
population control at the next trophic level down can affect the populations at the trophic level below.
Trophic cascades must occur across a minimum of three trophic levels (e.g. secondary consumer,
primary consumer, and producer). Trophic cascades can also happen from the bottom up; for example,
the removal of a producer may affect population sizes in the trophic levels above it.
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Suggested Lesson Flow Part 1:
1. Discuss the words habitat, apex predator, keystone species, and trophic cascade with students
and have them define these words in their notebooks. This may require a review of the structure of
food chains (producer, primary consumer/herbivore, secondary consumer/carnivore, etc.) so that
the concept of a trophic cascade can be explained.
2. Distribute the student worksheet for Part 1. Show students the Wolves of Yellowstone | EARTH A
New Wild video clip from the beginning and stop at 2:36 minutes.
3. While students are watching the video have them start to draw the bubble map on the student
worksheet for Part 1. This map charts the changes in the ecosystem of YNP in the absence of
wolves. Students should also answer questions 2-4 during or after the video.
4. Go over the bubble maps with the students. The teacher answer key on pages 6-10 of this guide
provides one possible bubble map and answers for the other viewing questions and activities.
5. The graphs in the student worksheet for Part 1 were taken from a 2012 scientific journal article by
Ripple and Beschta. You may wish to go over some of the labeling on the graphs and the related
vocabulary. Students should be able to work through the data analysis on their own or in a small
group. The graphs will lead the students to an understanding of the actual trophic cascade that
occurred in the ecosystem when wolves were reintroduced.
6. Spend the next class period going over the student worksheet for Part 1 and checking for
understanding.
7. At this point you may wish to show the rest of the video and have students draw a bubble map
that indicates the changes to the ecosystem when the wolves were reintroduced. This will help to
wrap up the activity and illustrate the ecosystem changes that were observed in the study by
Ripple and Beschta. A bubble map template and video viewing questions for the remainder of the
video can be found on the student worksheet for Part 2. However, if you plan on doing the role-
playing activity in Part 2 of this lesson, you may wish to wait to show the conclusion of the video so
as not to influence student opinion prior to the role-playing activity.
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WOLVES IN YELLOWSTONE
Student Worksheet TEACHER ANSWER KEY
Part 1: Defining Trophic Cascade
1. Watch the Wolves of Yellowstone | EARTH A New Wild
(http://www.pbslearningmedia.org/resource/a58e3ca2-52ab-45f5-87ac-
26ee0d681146/wolves-of-yellowstone-earth-a-new-wild/) video clip from the beginning and
stop at 2:36 minutes. As you are watching, create a bubble map below that includes all of the
things that happened in the Yellowstone ecosystem in the absence of wolves. Add as many lines
and bubbles from the center bubble as needed.
Wolves
ABSENT
Elk gathered on
river banks and
ate shrubs/trees
Less shrubs/trees
on banks and elk
hooves causes
stream banks to
erode
Erosion caused
water to get
muddy and fish
suffered
Less shrubs/trees
= beavers can’t
build dams
Without beaver
dams fish,
amphibians had
no protection
Pollinators had
fewer flowers
Elk population
doubled
Elk overgrazed
entire park, lots
of vegetation
gone
Mammals like mice
& rabbits had
nowhere to hide,
population
declined
Grizzly bears
suffered without
berries as food
source
Elk ate berries
Songbirds had
fewer trees for
nesting
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© Janet Haas for The Nature Conservancy
2. Using your bubble maps as a guide, create a food chain of the three organisms that are involved
in a trophic cascade in Yellowstone National Park.
3. With the elimination of wolves from the ecosystem, how was the population of plants (producers)
indirectly affected?
Answer: The population of plants was reduced because of the overgrazing of plants by elk.
Overgrazing occurred because the elk population was no longer controlled or checked by the
wolves (their predator).
4. Predict what would happen to the wolf and elk populations if there was a drought that caused
many of the plant species to dry up and/or die.
Answer: The elk population would decrease because its food source is decreased. This would also
cause the wolf population to decrease because they would have less food (elk).
Background:
The graphs in the next section were taken from the
2012 study by William Ripple and Robert Beschta on
trophic cascades in Yellowstone National Park. Aspen,
willow, and cottonwoods are common foods for
browsers like elk. Willows are also commonly eaten by
beavers. If scientists want to measure trees and shrubs
to look for the impact that browsers are having on their
growth, they might measure the following things:
Height
Recruitment
# of Rings
A measure of height can tell scientists how tall the trees are allowed to grow. If the mean tree height in
one area is low compared to another area that could be an indication of heavy browsing by elk.
Recruitment is the growth of seedlings or sprouts above the level of browsers. In other words, the trees are
able to grow taller than the level at which elk and other browsers can eat them. Tree rings indicated the
age of a tree the more rings a tree has, the older it is. Increases in these three measurements can
indicate an increase in the level of health of the woody plants. Decreases in these measurements could
indicate a higher level of browsing pressure on the plants.
Wolves
(secondary consumer or
carnivore)
Elk
(primary consumer or
herbivore)
Plants
(producers)
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Wolf Population
Elk Population
Use the graphs below to answer questions 5-8.
5. You have already identified that wolves are a predator of elk. Describe the general trend of the
elk and wolf populations between 1993 and 2003.
Answer: In 1994 the population of elk increased slightly and was just under 20,000 individuals.
However, from that point on the general trend was population decrease. By 2003 the number of
elk was just below 10,000 individuals. During the same period, the wolf population trend was to
increase. The wolf population rose from 0 to 100 during that period.
6. Based on the graphs, what year do you think wolves were introduced to Yellowstone? Explain why
you think this.
Answer: The wolves were introduced in 1995. The wolf population in 1994 was zero and in 1995
the count was around 20 individuals.
7. Using information from the graphs, describe what happens to the wolf and elk populations in
2005. Indicate what you think might have happened during this year to cause this change.
Answer: In 2005 there was a slight uptick in the elk population and a decrease in wolves. Wolves
could have died or left the park and the decrease in wolf population allowed for an increase in
elk population since there was less predation.
8. In 2010, the wolf population was lower than in previous years. Make a prediction about the elk
population in the years beyond 2010 if the wolf population continues to stay at the 2010 level.
Answer: Based on what happened to the elk population when the wolf population decreased in
2005, it is possible that the elk population will increase and continue to increase unless wolf
numbers increase. Just like when there were no wolves in the park, the elk population grew
unchecked.
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Examine the graphs below and use them to answer questions 9 and 10.
Note that the willow tree rings were measured in two different species of willow (Geyer and Booth). The
aspen heights were measured in two different habitats the uplands and riparian (stream side). During the
aspen measurements, it was also noted if there were logs in the area since logs could impede browsers
from getting to the trees, which would possibly decrease herbivory on those trees. In the cottonwood
recruitment graph, the measurement “>5cm DBH” means that the scientists measured the number of trees
that had reached a “diameter at breast height” greater than 5 cm.
9. Use information from the graphs to describe the change in the size and growth of the trees and
the population of elk during the data collection periods depicted in the graphs.
Answer: As the elk population began a general decline (after 1995), there was an increase in
willow tree ring area until around 1999. Between 2003 and 2004 the number of cottonwood that
were able to grow to a diameter greater than 5 cm also increased and kept increasing through
the end of the data collection period. Additionally, the mean aspen heights of all trees (with and
without logs, riparian and uplands) increased from the beginning of the data collection period in
1998 through the end of the data collection period in 2010.
10. What can you infer about the relationship between elk population and tree growth?
The decrease in elk allowed for the increase in growth of their preferred browsing plants
cottonwood, aspen, and willow.
Mean Aspen Heights
(early spring after winter browsing but
before summer growth)
Willow Tree Ring Area
(in Geyer and Booth species)
Cottonwood Recruitment
Elk Population
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Use the graphs below to answer questions 11-13.
11. Describe what happened to beaver colonies after 1995 (when wolves were reintroduced). Then
describe the relationship between the number of beaver colonies and the willow tree ring area.
Answer: Between 1995 and 1999, there was only one beaver colony counted. Beginning in 2000,
the colony count increased and by 2010, the count reached 12 colonies. The data on willow tree
ring area doesn’t include the entire time period that beaver data was collected. However, you can
see that between 1995 and 2000, the general trend was for an increase in tree ring area. This
indicates that there must have been less browsing pressure, which may have allowed willows to
grow more. At the time willow tree ring area reached its peak measurement in 2000
12. After about 1999, the willow tree ring area started to decrease again. What might account for
this decrease?
Answer: That decrease started about the same time the beaver population started to increase. It’s
possible the willow population rebounded after the decrease in elk population because of
decreased browsing pressures, but the small decrease reflects the increase in beaver herbivory of
the willow.
13. Based on what you know about tree growth and elk population, use data from the graphs to make
a statement about how the elk population impacts the beaver population. In your answer, address
why there was a lag between the change in elk population and the change in beaver population.
Answer: The elk population impacted the beaver population because when the elk population
decreased, the willow population was able to rebound and there was less competition with the elk
for woody plants. Even though the elk population dropped soon after the wolves were
reintroduced in 1995, the beaver population didn’t increase until the vegetation growth was well
underway. It took time for the plant communities to get established once there was less browsing
by elk.
# of Beaver Colonies
Willow Tree Ring Area
(in Geyer and Booth species)
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Other Resources for Part 1:
For more information and examples of keystone species:
http://www.nature.com/scitable/knowledge/library/keystone-species-15786127
For more information on trophic cascades:
http://www.nature.com/scitable/knowledge/library/trophic-cascades-across-diverse-plant-
ecosystems-80060347
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Part 2: Evaluate Solutions for Maintaining Ecosystem Services and Biodiversity
Purpose: In this activity, students will examine the pros and cons of various scenarios that were presented
by the U.S. Fish and Wildlife Service during the 1994 decision-making process on whether or not to
reintroduce wolves to Yellowstone National Park. During a role-playing activity, students will represent
various stakeholder opinions on reintroduction and will choose a scenario to support that best fits their
characters’ needs. They will share their characters’ opinions during a mock public forum and then students
playing the role of U.S. Fish and Wildlife Service Employees with select the best scenario for the park
after a thorough review of the benefits and constraints of each proposal. Students will learn that
ecological issues are complex and that there are no perfect solutions. This activity forces students to
evaluate the alternatives, find the best solution, and learn how to compromise for the best outcome.
Time: Two to three 45-minute class periods
Materials:
2 different colors of paper (green and yellow or your choice) for making role-playing cards
Copies of the role-playing materials described below:
URL for all role-playing materials: www.pbslearningmedia.org/resource/d4d90967-8a6a-4dcf-
8b65-3805d4781f24/wolves-of-yellowstone-part-2-student-role-play-materials
o Copies of Role-playing cards (one card per student, see instructions)
o Copies of Wolf Reintroduction Scenarios Pro and Con Chart (one per student)
o Copies of Wolf Reintroduction Scenarios Matrix (one per student)
o 1 copy of the USFWS Employee Prompt Card for Public Meeting
Copies of student Worksheet for Part 2 (one per student)
URL: www.pbslearningmedia.org/resource/fbf68a2a-27cc-4a88-a1e0-9898fe5a88be/wolves-
of-yellowstone-part-2-student-worksheet
Objectives:
The student will…
Interpret the scenarios proposed by the U.S. Fish and Wildlife Service (USFWS) regarding wolf
reintroduction to Yellowstone National Park (YNP).
Evaluate scenarios based on their ability to maintain or increase ecosystem services for humans
and support biodiversity in the park.
Evaluate the constraints of proposed scenarios.
Describe the differing viewpoints that existed during the decision-making process to reintroduce
wolves to YNP.
Utilize public feedback when choosing the best solution for wolf reintroduction to YNP.
Understand the complexity of environmental issues.
Collaborate with stakeholders to make a decision and propose the decision in a “public forum”.
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Next Generation Science Standards:
Disciplinary Core Ideas:
LS2.A: Interdependent Relationships in Ecosystems
LS2.C: Ecosystem Dynamics, Functioning, and Resilience
LS4.D: Biodiversity and Humans
ETS1.B: Developing Possible Solutions
Crosscutting Concepts:
Cause and Effect
Stability and Change
Science and Engineering Practices:
Engaging in an argument from evidence
Obtaining, evaluating, and communicating information
Performance Expectations:
Middle School
MS-LS2-5. Evaluate competing design solutions for maintaining biodiversity and ecosystem services.
High School
HS-LS2-6. Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain
relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result
in a new ecosystem
HS-LS2-7. Design, evaluate, and refine a solution for reducing the impacts of human activities on the
environment and biodiversity.
Vocabulary:
Biodiversity: the existence of a wide range of different types of organisms in a given place.
Ecosystem services: the benefits for humans that arise from heathy ecosystems; these benefits include but
are not limited to water purification, crop pollination, and a variety of recreational and cultural
benefits.
Suggested Flow for Part 2:
Pre-lesson preparation:
1. Photocopy one copy of each of the Wolf Reintroduction Scenarios Pro and Con Chart and Wolf
Reintroduction Scenario Matrix for each student (found on pages 1, 2, and 4 of the role-playing
materials sheets for Part 2).
2. Photocopy one set of the 12 role-playing cards found on pages 5-7 of the role-playing materials
for Part 2. It might be helpful to photocopy these on colored paper. The 12 cards represent voices
from the public. Their attitudes and opinions reflect some of the actual public commentary that
occurred during the decision-making process in 1994 (see Environmental Impact Statement). On
page 8 of the role-playing materials for Part 2 you will find a set of four U.S. Fish and Wildlife
Service cards. Photocopy enough of these cards for the remaining students in your class and use a
DIFFERENT color of paper than what you used for the first 12 cards. The different color cards will
make it easy for you to separate the two groups during the role play.
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3. Cut out the role-playing cards.
4. You can assign students to the different roles or hand out the role cards randomly during class.
During class:
5. If your students don’t already know what an ecosystem service is, use the beginning of class to
address this concept. Ecosystem services are the benefits for humans that arise from heathy
ecosystems; these benefits include but are not limited to water purification, soil erosion protection,
crop pollination, and a variety of recreational and cultural benefits. Recreational benefits can
include hunting and fishing as well as hiking and camping. It may be helpful to make a list of
ecosystem services on the board that students can reference during the role play. It will be useful
when students complete the Wolf Reintroduction Scenarios Matrix.
6. Distribute the Wolf Reintroduction Scenarios Pro and Con Chart and provide the following
background to students:
Prior to the reintroduction of wolves in Yellowstone National Park, the U.S. Fish and Wildlife Service
had to examine the feasibility of five different scenarios concerning wolves and Yellowstone National
Park. The pros and cons of the scenarios are described on your handout. The classifications
“experimental” and “non-experimental” are used in the Endangered Species Act of 1973, which helps
to define how endangered or threatened species are managed in the United States.
As of the time of this decision in 1994 there were no known wolf populations in Yellowstone National
Park.
Your job is to read over the pros and cons for each scenario and decide which scenario your character
would most likely choose and defend during a public hearing. If you are a U.S. Fish and Wildlife
Service (USFWS) employee, you goal is to evaluate the scenarios and listen to the public arguments
for and against each scenario. Ultimately, the USFWS will choose one scenario regarding wolf
reintroduction. It is possible to modify the scenarios, so keep this in mind as you listen to the public
commentary.
7. Let students look over the pros and cons and then ask if there are any questions. Make sure they
understand what is being proposed in each scenario before moving on.
8. Once students have looked over the pros and cons have them write a short paragraph in which
they state the scenario that their character will support and explain the reasons why they support
it. This will be used during the role-play. Both the public and the USFWS employees should
complete this task.
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9. In this role play there will be an inner circle and an outer circle. The inner circle will represent 12
voices from the public with regard to the reintroduction of the wolves to Yellowstone National
Park. The outer circle will represent U.S. Fish and Wildlife Employees who must ultimately make the
decision about wolf reintroduction.
10. Elect a student representative from the USFWS group to begin the discussion and serve as
moderator. There is a USFWS Employee Prompt Card on page 3 of the role-playing materials for
Part 2 they can use to start the public meeting. This prompt card instructs the “public” students
what to do during the forum. Students can use their own names for the purpose of introduction
during the role play, but otherwise, all students are assuming a completely different role and their
attitudes reflect the opinions of their character. This portion should last about 20-25 minutes.
11. Make sure to remind students in the role as USFWS employees that they should be taking notes
during the public comment period. USFWS employees may not talk until the question and answer
period at the end.
12. When the public forum is over, the inner and the outer circles should switch places, this time the
USFWS employees will enter the center circle and the public will move to the outer circle. You can
elect another moderator for this round or you can use the same moderator throughout the two
rounds. This moderator should make sure that everyone gets a chance to speak.
13. For this round, the USFWS employees will discuss which option seems best considering the views of
the public and the desire to maintain ecosystem services for humans (e.g. clean air and water,
nutrient cycling, prevention of soil erosion, recreational opportunities, ecotourism, etc.) while at the
same time maintaining biodiversity in the park.
USFWS Employees
Public
USFWS Employees
Public
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14. The moderator will guide the discussion and project the Wolf Reintroduction Scenarios Matrix.
USFWS employees will volunteer information to help complete the matrix. They will need to
decide which ecosystem services are promoted by the scenario and also include design
constraints for each scenario; these could include social, scientific, and economic limitations. It is
possible for the USFWS to make modifications to the scenarios to deal with the possible constraints
and to support ecosystem services. They should use their notes from the public hearing and the
pro/con sheet to guide their discussion.
15. While the USFWS are discussing the best scenario to choose and if there should be any
modifications, the students representing the public should be taking notes on the course of the
discussion and making note of how their concerns were addressed. They should also complete the
Wolf Reintroduction Scenarios Matrix along with the USFWS. The public may not comment during
this time. This round should last about 20-25 minutes. The answer key for the Wolf Reintroduction
Scenarios Matrix is on page 17 of this guide.
16. If your class periods are only 45 minutes long, you may wish to start the next round during the
next class period. After the USFWS employees have discussed which scenario they feel would best
fit, if it seems unanimous, they can propose that scenario to the public. If there are still
disagreements, they could do a majority rules vote or however you would like them to come to a
decision. This should take about 10-15 minutes.
17. The USFWS employees will then announce their decision and supporting reasons to the public. If
they have decided to make any modifications to the alternatives, they should explain how they
have modified the initial proposal and give reasons why. This should take about 5 minutes.
18. After the announcement, they can ask the public if they have any remaining concerns and if they
have ideas about how to address these concerns.
19. At the conclusion of the role play, have students write a short reflection about the process. If they
were on the USFWS side of the role play, they should write about the challenges in coming up with
an acceptable proposal that balances the needs of the park and YNP ecosystem with the
demands of the public. If the students were members of the public, they should write a reflection
on how they felt about the final decision given the needs of their particular character. Students
should also include in the reflection if their final decision differs or is similar to the scenario chosen
by the USFWS.
20. Collect the reflections and debrief with the class during the next class period.
21. At this point, you may want to share with students that the USFWS service ultimately chose scenario
#1 with a few modifications based on public comment.
22. To illustrate to the students the impact that the wolves had on Yellowstone, show the remainder of
the Wolves of Yellowstone | EARTH A New Wild video (2 min, 40 sec) and have students do a
second bubble map on the conditions in YNP when the wolves are PRESENT. There is a bubble map
and two viewing questions on the student worksheet for Part 2 that you can print and distribute to
students. Answers can be found on the teacher answer key for Part 2 on page 18 of this guide.
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Part 2: Wolf Reintroduction Scenarios Matrix TEACHER ANSWER KEY
Scenario #1:
Reintroduction of
experimental wolves
Scenario #2: Natural
recovery
Scenario #3:
No wolves wolf
prevention
Scenario #4:
Local wolf
management
committee
Scenario #5:
Reintroduction of non-
experimental wolves
Ecosystem
Services
Ecotourism, hunting,
soil erosion, water
filtration. However,
because wolves can
be shot if they impact
livestock, it may make
it harder to establish
a population.
None likely.
None, ecosystem will
continue to be
degraded.
Ecotourism, hunting (if
some states allow that
to control wolves),
possible soil erosion
protection and water
filtration.
Wolves will keep the
elk population in
check and trees and
other plants will
rebound. Ecotourism,
water filtration,
prevention of soil
erosion.
Constraints
How will the wolves
that impact livestock
be managed? The
wolves aren’t as
protected, so it might
be harder for a
population to get
establish.
If there are no wolves
in Yellowstone now
(1994), then the only
way they would
naturally get there is
to migrate into the
park. However,
wolves have not
migrated into the park
and been successful
since they were
eliminated in the
1920’s.
Elk population will
continue to grow,
which will inevitably
impact YNP and could
extend beyond the
park’s boundaries to
impact other areas
This might make
ranchers and other
locals happy. But
because wolves will
be managed
differently in every
state, what happens if
wolf populations
migrate from state to
state?
This scenario would be
the least likely to
make ranchers happy.
If their livestock are
killed, they may want
to kill the wolves and
there will be conflict
with local communities.
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WOLVES IN YELLOWSTONE
Student Worksheet TEACHER ANSWER KEY
Part 2: Evaluate Solutions for Maintaining Ecosystem Services and Biodiversity
Watch the Wolves of Yellowstone | EARTH A New Wild
(http://www.pbslearningmedia.org/resource/a58e3ca2-52ab-45f5-87ac-26ee0d681146/wolves-of-
yellowstone-earth-a-new-wild/) video clip in its entirety and answer the questions below:
1. How have wolves helped the economy in the Yellowstone National Park area?
Answer: In 2005, there were over 100,000 visitors to YNP who came to see wolves. This brought
about 30 million dollars into the local economy.
2. What are other consequences of wolf introduction that have been good for the humans in the
area?
Answer: For the 106,000 residents of Billings, Montana, the Yellowstone River is cleaner and
provides better drinking water for the community.
3. Complete the bubble map below and include all of the changes to the ecosystem AFTER wolves
were reintroduced. Add as many lines and bubbles from the center as needed.
Wolves
PRESENT
Elk are chased
from river bank
by wolves
Stream banks
stabilizing, less
erosion
Water quality
improving
More trees for
beavers to build
dams
Fish and
amphibians have
protection from
dams
More plants means
more flowers for
pollinators
Elk population
reduced from
17,000 in 1995 to
4,000 in present
day
https:/
/www.
nature
Fewer elk
means less
overgrazing
Mammals like
mice & rabbits
have more
hiding plants
and population
increases
Grizzly bears
have more food
available
More berries
available to
bears
Songbirds had
more trees for
nesting
Trees
(aspen/willow)
growing again
https:/
/www.
nature
Only healthy elk
survive wolves
kill weak and
old
https:/
/www.
nature
Elk population
stronger,
healthier
https:/
/www.
nature
Elk carcasses
benefit
scavengers and
bears
19 | Tea c h e r G u i d e - W o l v e s o f Y e l l o w s t o n e
Part 3: Twenty Years After Wolf Reintroduction to Yellowstone
Purpose: Nearly twenty years has passed since the reintroduction of the wolves, and there has been a
variety of research on the actual impact of the wolves to YNP. The purpose of this activity is to allow
students to examine the research and to determine the actual impact of the wolves on the park and relate
it to the initial public concerns that were expressed in the role-play activity in Part 2.
Time: Two 45-minute class periods, with homework
Materials:
Computers and internet access for all students
Objectives:
The student will…
Identify and explore research that documents the changes in YNP since wolf reintroduction.
Determine if the concerns of the public during the public comment period have been manifested
over the last twenty years since the return of the wolves.
Evaluate if the decision that was made (choosing scenario #1) actually yielded the desired results.
Next Generation Science Standards:
Disciplinary Core Ideas:
LS2.A: Interdependent Relationships in Ecosystems
LS2.C: Ecosystem Dynamics, Functioning, and Resilience
LS4.D: Biodiversity and Humans
ETS1.B: Developing Possible Solutions
Crosscutting Concepts:
Cause and Effect
Stability and Change
Science and Engineering Practices:
Engaging in an argument from evidence
Obtaining, evaluating, and communicating information
Performance Expectations:
Middle School
MS-LS2-5. Evaluate competing design solutions for maintaining biodiversity and ecosystem services.
High School
HS-LS2-6. Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain
relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result
in a new ecosystem
HS-LS2-7. Design, evaluate, and refine a solution for reducing the impacts of human activities on the
environment and biodiversity.
20 | Tea c h e r G u i d e - W o l v e s o f Y e l l o w s t o n e
Suggested Flow for Part 3:
1. Assign students to one of the teams below. Have them conduct research to see if the concerns of
each role from Part 2 have been manifested in the last 20 years. Place two to three students on
each team. Place students on teams as it best suits your class size and access to computers for
research.
2. Students can use the hyperlinks provided as a starting point. You can share this page digitally in a
Google document or whatever works best for you and your students. They should find at least two
additional sources of reliable information (trusted resource) on the internet to support their
findings. The groups should prepare their research to share with the class and elect a speaker who
will summarize their findings.
Team #1: Describe how the wolves have impacted livestock in the area since 1994.
Start here: http://fwp.mt.gov/fishAndWildlife/management/wolf/history.html
http://www.fws.gov/mountain-
prairie/species/mammals/wolf/wyomingstatus2010/10012010.html
Team #2: Describe what has happened with Grey Wolf hunting restrictions since 1994.
Start here: http://www.nps.gov/yell/naturescience/wolfmgnt.htm
http://wgfd.wyo.gov/web2011/news-1002256.aspx
http://wgfd.wyo.gov/web2011/wildlife-1000380.aspx
Team #3: Describe how the wolves’ status as an endangered species has changed since 1994.
Start here: http://www.nps.gov/yell/naturescience/wolfrest.htm
Team #4: Describe how the Grey Wolves population has changed in the park area (MT, WY,
ID) since reintroduction.
Start here: http://www.fws.gov/mountain-prairie/species/mammals/wolf/
Team #5: Describe how many attacks by wolves on people and pets there have been in the
Yellowstone National Park area (Wyoming, Idaho, Montana) since 1994.
Start here: http://en.wikipedia.org/wiki/List_of_wolf_attacks_in_North_America
Team # 6: Describe how the reintroduction of wolves has impacted the local economy.
Start here:
http://www.cnn.com/2010/WORLD/americas/02/02/wolves.ecosystem.control.climate/
https://www.wildlifemanagementinstitute.org/PDF/11Social%20and%20Ecological....pdf
3. After completing their research and summarizing their findings, students can share their information
with the class through short presentations. Have a class discussion on how the wolf introduction has
impacted YNP over the last twenty years and how it has impacted the people that live in the area.
4. To conclude this activity, have students write a statement in which they analyze the cost and
benefits to the park and the community. They should include evidence from their research, the
research of the other groups, and any other relevant parts of this lesson.
21 | Tea c h e r G u i d e - W o l v e s o f Y e l l o w s t o n e
Part 4: Extend Knowledge Isle Royale National Park
Purpose: The purpose of this activity is to extend upon the knowledge students have gained in learning
about the trophic cascade that occurred in Yellowstone National Park (YNP). Because the reintroduction of
wolves in YNP occurred 20 years ago, there is already data that illustrates the effects of the
reintroduction. By investigating the situation on Isle Royale, students can use prior knowledge to evaluate a
modern situation in a different ecosystem with different constraints in order to propose a unique
management decision.
Time: One 45-minute class period plus homework
Materials:
Student access to computers and internet for research (can be done as homework)
Student copies of http://news.nationalgeographic.com/news/2014/04/140427-wolves-isle-
royale-animals-science-nation/ (or can be read online)
Student copies of http://blog.nature.org/science/2013/10/10/should-we-let-the-wolves-of-isle-
royale-disappear/ (or can be read online)
50 Years of Wolf and Moose Dynamics on Isle Royale graph on page 24 of this guide (can be
projected or provide students with copies)
Objectives:
The student will…
Examine and analyze data on wolf and moose dynamics on Isle Royale.
Describe the relationship between wolves and moose based on data.
Predict how future populations of wolves and moose will change based on evidence.
Propose management solutions for Isle Royale National Park that will ensure biodiversity, maintain
a healthy ecosystem, and maintain genetic diversity in the park.
Next Generation Science Standards:
Disciplinary Core Ideas:
LS2.A: Interdependent Relationships in Ecosystems
LS2.C: Ecosystem Dynamics, Functioning, and Resilience
LS4.D: Biodiversity and Humans
ETS1.B: Developing Possible Solutions
Crosscutting Concepts:
Cause and Effect
Stability and Change
Science and Engineering Practices:
Engaging in an argument from evidence
Obtaining, evaluating, and communicating information
22 | Tea c h e r G u i d e - W o l v e s o f Y e l l o w s t o n e
Performance Expectations:
Middle School
MS-LS2-2. Construct an explanation that predicts patterns of interactions among organisms across multiple
ecosystems.
MS-LS2-5. Evaluate competing design solutions for maintaining biodiversity and ecosystem services.
MS-LS4-4. Construct an explanation based on evidence that describes how genetic variations of traits in a
population increase some individuals’ probability of surviving and reproducing in a specific environment.
High School
HS-LS2-6. Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain
relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result
in a new ecosystem
HS-LS2-7. Design, evaluate, and refine a solution for reducing the impacts of human activities on the
environment and biodiversity.
HS-LS4-5. Evaluate the evidence supporting claims that changes in environmental conditions may result in: (1)
increases in the number of individuals of some species, (2) the emergence of new species over time, and (3)
the extinction of other species.
Suggested Flow for Part 4:
1. Before beginning this activity, it may be useful to share with students some information regarding
Isle Royale National Park.
A detailed map of the park can be found here:
http://en.wikipedia.org/wiki/Isle_Royale_National_Park#mediaviewer/File:IsleRoyaleM
ap.jpg
Information about the park can be found here: http://www.nps.gov/isro/index.htm
2. After introducing students to the park, have them compare and contrast the park with Yellowstone.
You could have students make a T-chart and compare the two. Because Isle Royale is on an island
and the park takes up the entire island, the situation is drastically different from Yellowstone.
Animal movement to and from the island can only happen via ice bridge in the winter and ice
bridges don’t form every year. Because the park is on an island, there aren’t the same issues with
ranching and hunting. The two articles will give more information on the park and they can add to
their T-charts as needed.
3. The graph on the page 24 of this guide represents 50 years of wolf and moose dynamics on Isle
Royale National Park in Michigan State. Share this with the class and have them describe the wolf
and moose population dynamics over time. For example, what happens to the moose population
when the wolf population increases? What happens to the wolf population when the moose
population increases? If you would like students to create their own graphs, the data can be
downloaded as an Excel spreadsheet at: http://www.isleroyalewolf.org/data/data/home.html
4. Ask students to speculate what might happen to the moose population after 2011 based on the
data in the graph and based on what they have learned about Yellowstone National Park.
5. Given their knowledge of what happened to Yellowstone National Park, have them describe what
might be the consequences to the ecosystem if wolves disappeared from the island permanently.
23 | Tea c h e r G u i d e - W o l v e s o f Y e l l o w s t o n e
6. Have students read this article from National Geographic, which gives details about the plight of
the wolves on Isle Royale: http://news.nationalgeographic.com/news/2014/04/140427-wolves-
isle-royale-animals-science-nation/
7. Also have students read this opinion on the Cool Green Science Blog about wolves on Isle Royale:
http://blog.nature.org/science/2013/10/10/should-we-let-the-wolves-of-isle-royale-disappear/
8. After reading both sources, have students develop their own opinions and write a position paper
about what should happen with the wolves on Isle Royale. They should cite evidence from the
National Geographic article and any other sources to support their management decision. They
should specifically address the following points:
Ensuring the biodiversity of the park
Maintaining a healthy ecosystem
Maintaining genetic diversity in the park
24 | Tea c h e r G u i d e - W o l v e s o f Y e l l o w s t o n e
0
10
20
30
40
50
60
0
500
1000
1500
2000
2500
3000
Number of Moose
50 Years of Wolf and Moose Dynamics on Isle Royale
moose
abundance
wolf
abundance
Number of Wolves
Wolf and moose data obtained from: http://www.isleroyalewolf.org/data/data/home.html
25 | Tea c h e r G u i d e - W o l v e s o f Y e l l o w s t o n e
Additional Resources:
Graph of wolf population trends from 1979-200 in NW Montana, Yellowstone, and Central
Idaho: http://www.fws.gov/mountain-prairie/species/mammals/wolf/annualrpt00/html/fig5.GIF
For more information on the wolves in Yellowstone story, check out this video by KQED:
http://www.pbslearningmedia.org/resource/20c3b7fd-080b-4c70-a9fa-
72c35899d815/wolves-the-ecology-of-fear/
For more information on trophic cascades in salmon ecosystems, check out this video by WNET:
http://www.pbslearningmedia.org/resource/nat11.sci.living.eco.salmeco/salmon-in-the-
ecosystem/
For another example of species reintroduction, check out this video by WNET on beaver
reintroduction in Alberta:
http://www.pbslearningmedia.org/resource/nat14.sci.lifsci.results/unexpected-results/
Bibliography:
Ripple, William J., and Robert L. Beschta. "Trophic Cascades in Yellowstone: The First 15 Years after Wolf
Reintroduction."Biological Conservation 145 (2012): 205-13. Web. 14 Jan. 2015.
<http://www.greateryellowstone.org/uploads/RippleBeschtaYellowstone_BioConserv.pdf>.
United States. National Park Service. "Wolf Restoration." National Parks Service. U.S. Department of the
Interior, 05 Jan. 2015. Web. 14 Jan. 2015. <http://www.nps.gov/yell/naturescience/wolfrest.htm>.
U.S. Department of the Interior, and Fish and Wildlife Service. The Reintroduction of Gray Wolves to
Yellowstone National Park and Central Idaho: Summary of Final Environmental Impact Statement.
Helena, MT: Fish and Wildlife Service, U.S. Dept. of the Interior, 1994. Web. 14 Jan. 2015.
<http://www.fws.gov/mountain-prairie/species/mammals/wolf/eis_1994.pdf>.
Vucetich, John A., and Rolf O. Peterson. "The Population Biology of Isle Royale Wolves and Moose: An
Overview." Wolves & Moose of Isle Royale. N.p., 2012. Web. 15 Jan. 2015.
<http://www.isleroyalewolf.org/data/data/home.html>.
Standards:
National Governors Association Center for Best Practices & Council of Chief State School Officers. Common
Core State Standards. Washington, DC: Authors, 2010.
NGSS Lead States. Next Generation Science Standards: For States, By States. Washington, DC: The
National Academies Press, 2013.