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Niche Partitioning Activity
Activity
Educator Materials
OVERVIEW
In this activity, students make claims about different niche partitioning mechanisms based on scientific data. The
activity begins with students interpreting a graph about dietary niche partitioning by grazers on the African
savanna. Students then watch two short videos, one on niche partitioning and the other on DNA metabarcoding,
and answer questions to apply what they have learned.
Additional information related to pedagogy and implementation can be found on this resource’s webpage
,
including suggested audience, estimated time, and curriculum connections.
KEY CONCEPTS
• Ecological communities are structured, in part, by interactions between different species.
• Niche partitioning is an example of cooperative behavior between populations that contributes to their
survival.
STUDENT LEARNING TARGETS
• Analyze graphs and explain trends in the data.
• Explain how behavior that benefits populations involves timing and coordination of activity.
• Describe different mechanisms of niche partitioning.
• Evaluate a classical understanding of niche partitioning in light of new data.
PRIOR KNOWLEDGE
It is helpful for students to have some familiarity with:
• the ecological concept of a niche
• species interactions, such as competition and facilitation
• different types of herbivores, such as grazers and browsers
• the African savanna ecosystem
• interpreting line graphs and scatterplots
MATERIALS
• copies of the “Student Handout”
• access to the “Niche Partitioning” and “Metabarcoding” video clips, which can also be downloaded from
this
activity’s webpage
TEACHING TIPS & SEQUENCE
• The “Student Handout” is designed to guide students through the activity at their own pace. However, you
might choose to begin with a discussion or to have all students work on the same section at the same time.
• In Part 1 of the activity, students interpret a line graph showing dietary niche partitioning by grazers on the
African savanna by time and grass height.
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This graph is based on Figure 2 from du Toit and Olff (2014). The same graph is also discussed at the end
of the “Niche Partitioning” video clip, which students will watch in Part 2 of this activity.
You may choose to quickly introduce the three grazers shown in Part 1: zebra, wildebeest, and
Thomson’s gazelle. For photographs of the animals, you could visit the African Wildlife Foundation’s
Wildlife Gallery, as well as WildCam Gorongosa’s Field Guide (on the Classify page) and Collections
.
You might choose to discuss the concept of a fundamental versus a realized niche, especially for zebra,
with the class. Ask students to brainstorm ways to test their ideas about zebras’ fundamental versus
realized niches. What other data would they need, and how could they collect it?
• In Parts 2 and 3 of the activity, students watch two video clips from the 2015 Holiday Lecture
“How Species
Coexist” to learn more about niche partitioning and how it is studied.
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Both video clips can be accessed via the links below or downloaded from this activity’s webpage. The
“Student Handout” also contains the links provided below.
The first video clip, “Niche Partitioning,” describes several classical niche partitioning mechanisms. It
provides examples of herbivores in the African savanna partitioning their habitat by space (spatial niche
partitioning) and diet (dietary niche partitioning), the latter of which may involve dividing food resources
based on time or height (as shown in Part 1 of this activity).
The second video clip, “Metabarcoding,” describes a technology that allows scientists to determine
herbivore diets based on the sequences of plant DNA extracted from animal dung.
After watching the second clip, students are asked to interpret a graph of herbivore dietary differences.
This graph is based on Figure 4a from Kartzinel et al. (2015)
and uses data from DNA metabarcoding.
It also appears in the “How Species Coexist” Holiday Lecture starting around 16:33.
This graph was generated using nonmetric multidimensional scaling. NMDS is briefly described in
the “Student Handout” but may be unfamiliar to students. If students are struggling with this graph,
consider discussing it as a class and/or providing additional support.
• Part 4, the last part of the activity, has students apply niche partitioning concepts. You can have students do
the Part 4 questions individually, or you can pose them as small-group or large-group discussion questions.
• This activity can be supplemented with related resources, such as the following:
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Mu
ltiple BioInteractive resources allow students to apply concepts from this activity to other examples.
For instance, the short film The Origin of Species: Lizards in an Evolutionary Tree and the
Lizard Evolution
Virtual Lab explore niche partitioning in anole lizards.
Other resources, such as the article “Humanity’s Grassroots: How Grazing Animals Shaped Evolution”
and the corresponding PNAS paper (Uno et al. 2011), could be used to explore the history and
importance of grazers in the African savanna.
ANSWER KEY
PART 1: Niche Partitioning by Time and Grass Height
1. Describe how the relative zebra density changes over time. What characteristics of zebras could explain why
zebra densities are greatest when the P. maximum grass is tallest and most abundant?
Right after the peak rain, zebras have the highest relative density of all three grazers. The zebra relative
density reaches its maximum one month after the rain, decreases to nearly zero three months after the
rain (when the wildebeest density is highest), and then increases to about 0.3 six months after the rain.
The reason that zebra densities are greatest when the grass is tallest and most abundant is because, out
of these three grazers, zebras get the most out of eating tall grass. Zebras’ teeth allow them to eat taller
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grasses with many stems. Zebras can also digest grass faster. Although their digestion is less efficient than
that of the ruminant grazers, and the tall grass is less nutritious because it has many stems, zebras can
just eat a lot of the grass and digest it quickly to get the nutrition they need.
2. D
escribe how the relative wildebeest density changes over time.
The relative density of the wildebeest population is nearly zero for two months after the peak rain,
increases to its maximum three months after the rain, then declines to nearly zero again by five months
after the rain.
3. P
ropose a reason or reasons why the relative wildebeest density spikes when it does. Support your idea with
evidence from what you know about wildebeests and P. maximum grass. (Hint: Remember that the more
nutritious parts of the grass are closer to the ground. The grasses continue to grow after being grazed, and
the parts that grow back are also more nutritious.)
The wildebeest density spikes about three months after the peak rain. By this point, the P. maximum grass
has already been grazed by zebras, which were most common in the months prior. The zebras eat the tops
of the grass, making it easier for wildebeests to access the more nutritious parts of the grass near the
ground. The parts of the grass that grow back after the zebras graze are also more nutritious.
Since wildebeests are ruminants, they cannot digest food as quickly as zebras do, but they can get more
energy and nutrients from a smaller amount of food. So, it is probably advantageous for them to eat the
grass that the zebras have grazed even if it is not as tall, since it is more nutritious.
4. Describe how the relative Thomson’s gazelle density changes over time, in relation to the changes in the
wildebeest population density and in the grass height. Why do you think this is so?
The relative density of the gazelle population is low (around 20%–30%) until 2 months after the peak rain,
at which time it begins steadily increasing to its maximum, at about 5 months after the rain. By this point,
the wildebeest relative density has returned to nearly zero, and the grass height is very short.
In
general, it appears that the gazelle density increases as the grasses get shorter due to grazing by the
zebras and wildebeests. This could be because, like wildebeests, gazelles are ruminants that benefit from
more nutritious food even if it is less abundant. When the grasses are grazed by other animals first, the
gazelles have greater access to the more nutritious parts. Because gazelles are smaller than wildebeests,
they need less energy overall. So they can thrive on the shortest grass even if the other animals cannot get
enough energy from it.
5. W
ould you describe the interactions between zebras, wildebeests, and Thomson’s gazelles as competition
or facilitation among species? Support your answer with data from Figure 1.
Student answers may vary but should be supported with logic and evidence from the graph above. Note
that ecologists tend to view this as a positive interaction, such as facilitation, rather than a competitive
one.
PA
RT 2: Types of Niche Partitioning
6. Co
mplete the following table based on what you learned. Include both a general description and a specific
example for each row.
Student examples may vary. Sample answers are provided on the next page.
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Type
Example
Spatial niche
partitioning
different spaces in a
habitat.
Different antelope species live in different places in the
same habitat (reedbuck in the reeds, nyala in the woods,
etc.).
Dietary niche
partitioning
different things.
Some herbivores, such as zebras, eat mostly grass. Others,
such as dik-diks, eat mostly other plants like shrubs and
trees.
Niche partitioning
by resource height
resources at different
heights.
Tall herbivores, such as giraffes, usually eat from the higher
parts of a tree. Shorter herbivores, such as kudu or
steenbok, eat from the lower parts of a tree.
Niche partitioning
by time (temporal
niche partitioning)
resources at different
times.
As shown in Part 1, zebras, wildebeests, and Thomson’s
gazelles eat P. maximum grass at different times after the
peak rain. Zebras eat the grass right after the rain, when it
is tallest, and gazelles eat the grass several months after,
when it is shortest. Wildebeests eat the grass in between
these two periods, when it is of intermediate height.
PART 3: Investigating Dietary Niche Partitioning with Metabarcoding
7. In general, how does the diet of the plains zebra compare to that of the Grevy’s zebra? Are they eating the
same species of plants?
Figure 2 shows that the data points for these species are in distinct clusters with some overlap. This
suggests that the two species have distinct diets and do not eat all of the same plants. However, there are
probably some types of plants they both eat because there is some overlap in their diets.
8. I
n general, how does the diet of the plains zebra compare to that of the impala?
Figure 2 shows that the data points for these species are in distinct clusters without any overlap. This
suggests that they have very different diets.
9. H
ow might the data in Figure 2 provide a greater understanding of the grazer-browser spectrum?
Figure 2 supports the grazer-browser spectrum by showing separation among the diets of grazers and
browsers along the x-axis. However, the figure adds to our understanding of the spectrum by showing
additional variation within grazers or browsers along the y-axis. For example, although zebras are all
grazers, different species of zebras (plains and Grevy’s) do not have the exact same diets and are probably
eating some different species of plants.
10. F
igure 2 includes six wild species and one domesticated species: cattle. How might these data inform wildlife
management near areas with farming and/or ranching of domesticated animals?
These data could help determine whether the wild and domesticated species eat the same types of plants
and would thus compete for food. This information could help farmers and ranchers decide when it would
be useful, or not useful, to remove or restrict wildlife from their lands.
11. Th
e data in Figure 2 are from a single wet (rainy) season. Why would it be important to run the experiment
again during other seasons?
In other seasons, there may be less rain and thus fewer plants, so animals may have to shift their diets. If
so, the patterns shown in Figure 2 could change. The species’ diets might begin to overlap more, especially
if there are fewer plants to choose from, or they might shift to other distinct diets.
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PART 4: Applications of Niche Partitioning
12. For each of the examples in the following table, identify the mechanism by which the resources, and thus
the niches, are divided. Use the niche partitioning mechanisms you described in Question 6.
Mechanism
Description and example
Niche partitioning by time
During the warm daylight hours, bees collect nectar from the
flowers on a linden tree. In the evening, different types of moths
are on the flowers.
Dietary niche partitioning
Two types of birds, pileated woodpeckers and yellow-bellied
sapsuckers, get food from the same tree. Sapsuckers drill rows of
little holes to eat the tree’s sap and insects in the sap. Pileated
woodpeckers dig deep holes to find insects in the tree trunk.
Spatial partitioning
or
Niche partitioning by resource
height
Prairie grasses use their roots to get water and nutrients from the
soil. Smartweed roots reach nearly 100 cm underground, Indian
mallow roots reach 70 cm, and bristly foxtail roots reach only
about 20 cm.
13. Which of the following statements best describes niche partitioning?
a. Varying prey species maintains biodiversity.
b. Superior species enjoy success because of competitive exclusion.
c. Coevolution between two species means they can always share the same niche.
d. Similar species can coexist because of slight differences in each one’s niche.
14. How can niche partitioning increase biodiversity?
Niche partitioning can increase biodiversity by giving multiple species access to a limited resource. By
dividing up the resource in such a way that the species don't have to compete with one another, a greater
number of species are able to survive.
REFERENCES
Du Toit, Johan T., and Han Olff. “Generalities in grazing and browsing ecology: using across-guild comparisons to
control contingencies.” Oecologia 174, 4 (2014): 1075–1083. https://doi.org/10.1007/s00442-013-2864-8
.
Griffin, John N., and Brian R. Silliman. “Resource Partitioning and Why It Matters.” Nature Education Knowledge
3, 10 (2011): 49. https://www.nature.com/scitable/knowledge/library/resource-partitioning-and-why-it-
matters-17362658/.
Kartzinel, Tyler R., Patricia A. Chen, Tyler C. Coverdale, David L. Erickson, W. John Kress, Maria L. Kuzmina, Daniel
I. Rubenstein, et al. “DNA metabarcoding illuminates dietary niche partitioning by African large herbivores.”
Proceedings of the National Academy of Sciences 112, 26 (2015): 8019–8024.
https://doi.org/10.1073/pnas.1503283112
.
CREDITS
Written by Susan Dodge, consultant
Edited by Esther Shyu, Mark Nielsen, Aleeza Oshry, HHMI