Teacher Copy, Level 2
Name_________________
Which guy should she choose?
Featured scientist: Alycia R. Lackey from Michigan State University
Research Background:
In many animals, males use complex
behaviors to attract females. They
use displays to show off colorful
parts of their bodies, like feathers or
scales. For example, male peacocks
fan out and shake their colorful tails
to attract female attention. These
displays take up a lot of energy, and
yet some males are unable to attract
any females while other males attract
many females.
In stickleback fish, males are very
colorful to attract females. Their
Figure 1: A male stickleback tending his nest. Notice the
male’s bright red throat, blue eye, and blue-green body.
throats turn bright red during the
spring when they mate. Stickleback
males also court females with zig-zag swimming! The males swim in a z-shaped
pattern in front of the female, probably to show off their mating colors. Before male fish
can get the attention of female fish, they must gain a territory and build a nest. In
sticklebacks, females inspect nests that the males build and then decide if they want to
deposit their eggs. Males care for the offspring before and after the eggs hatch. A
female fish would benefit from identifying “high quality” males and choosing those
males for mates. High quality males would have more energy to protect their offspring
and would make better fathers. They could also pass on genes that make offspring
more attractive to females in the next generation.
Alycia is a scientist who is interested in the stickleback’s mating behaviors. She
wanted to figure out why there are differences between males and why certain males
can attract a mate while others cannot. What is it about the way a male looks, moves,
or smells that attracts females? What male traits are females looking at when deciding
on a mate? Alycia thought female sticklebacks may choose males with redder throats
and/or more complex behaviors because those traits show the female that those males
are high quality. Previous work with these fish showed that male behavior, color, or
territory size, or the presence of a nest could all be important. But it was still not clear
which characteristic might be most important.
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Teacher Copy, Level 2
Alycia set up an experiment
to figure out if male throat
color or zig-zag swimming
behaviors were attractive to
females. She used a total of
24 male fish and six 75gallon tanks. She divided the
males up evenly between the
large tanks, placing four
males in each one. For 10
days she observed the male
fish and recorded
competition behaviors,
territory defense, and nest
building. On the tenth day,
she introduced one female to
each tank of four males. She
recorded how the males
behaved in courtship and
which males the females
chose. She also recorded
the redness of each male.
Name_________________
Figure 2: Scientist Alycia collecting fish from a freshwater lake in
British Columbia, Canada.
For each of the 24 male fish studied, Alycia collected the following data:
1. Female preference score: The higher the number, the more the female was
attracted to that male. The scores were given as follows: (0) the female did not
respond to the male, (1) the female approached the male, (2) the female followed
the male to his territory, and (3) female examined the male’s territory, poking her
head into the sand to look for a nest.
2. Male courtship behaviors: number of display zig-zag dances the male did per
minute.
3. Redness of male throat: The higher the number, the more red the male’s throat
was. This score includes both the area covered by and the intensity of red
coloration on each male fish’s throat.
4. Territory size: Each male’s territory size was categorized as small if it was
smaller than half the tank and large if it was larger than half the tank.
5. Presence of nest: whether or not the male fish made a nest.
Check for Understanding: After reading the Research Background, students should be
able to:
• give an example of a trait and of a display behavior in male stickleback fish.
• describe why it is important that female sticklebacks choose high quality mates. Who
cares for the eggs once they are laid in the nest?
• describe, in their own words, the experimental design. How many male and female fish
were in each tank? What data did Alycia collect?
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Teacher Copy, Level 2
Name_________________
Scientific Questions: Does male throat redness and courtship behavior influence which
males females choose, and if so, how?
What is the hypothesis? Find the hypotheses in the Research Background and
underline them. A hypothesis is a proposed explanation for an observation, which can
then be tested with experimentation or other types of studies. Having two alternative
hypotheses means that more than one mechanism may explain a given observation.
Experimentation can determine if one, both, or neither hypotheses are supported.
Scientific Data:
Use the data below to answer the scientific questions:
Female
Preference Male Courtship Redness of
Presence of
Score
Behavior
Male Throat Territory Size
Nest
(none, small,
(0-3)
(# per minute)
(0-10)
(yes or no)
large)
0
1.75
5.0
Large
No
0
0.28
5.0
None
No
0
0.00
7.0
None
No
0
0.74
5.0
None
No
0
0.11
3.0
None
No
0
1.20
4.0
Small
No
0
0.28
6.5
Small
No
0
0.49
5.5
Large
Yes
0
1.55
6.5
Small
Yes
1
2.57
7.5
Large
No
1
6.48
7.0
Large
No
1
1.89
7.5
Large
No
1
0.48
5.0
None
No
1
0.14
8.0
Small
No
1
8.04
7.5
Large
Yes
1
0.38
7.5
Small
Yes
1
3.81
8.0
Small
Yes
2
8.23
8.0
Large
No
2
10.00
6.5
Small
No
2
11.07
6.0
Small
No
2
1.87
6.5
Small
Yes
3
3.30
6.0
Large
Yes
3
12.93
7.0
Large
Yes
3
12.72
7.5
Large
Yes
Data Nuggets developed by Michigan State University fellows in the NSF BEACON and GK-12 programs
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Teacher Copy, Level 2
Name_________________
What data will you graph to answer the questions?
Independent variables: Male courtship behaviors (#/min) &
Redness of male throat
Dependent variable: Female preference score
Meta Moment: Have students reflect on how they were able to use what they learned about
sticklebacks in the Research Background to select the data they would use to answer the
scientific questions.
Teacher Note: The students will not need to graph all the data in the table in order to
address the research questions. You may want to ask them to think about which of the
variables are relevant to address the hypotheses most effectively and why.
• Ask the students to review the hypotheses. When they do this, they should be reminded
that Alycia thought that female sticklebacks would be more attracted to males with redder
throats and more complex courtship behavior.
• Therefore, students should choose
o the Female preference score as a means of determining how attracted the
female sticklebacks are to the different males.
o the Redness of male throat.
o the Male courtship behavior.
• Some students may argue that the territory size and the presence of a nest could be
included as part of the complexity of male behavior. If you have time for an extension to
this activity, you could ask the students to create graphs to demonstrate the results of
these variables as well.
In this experiment there are multiple independent variables, meaning that more than one
variable may be influencing female mate choice. It is possible to test multiple variables at
once in a single experiment. Having multiple independent variables can mean you are testing
more than one hypothesis, called alternative hypotheses. Discuss with students what it
means to have alternative hypotheses—more than one mechanism may be operating in this
system at a time, influencing our observations. In sticklebacks, females may prefer males
with redder throats, or not. They may also prefer males that do more zig-zag dances, or not.
Neither mechanism is mutually exclusive; one, both, or neither may be operating.
Check for Understanding: After taking some time to look at the data table, have students
discuss the question, “What type of graph should you make?” There are many different
kinds of graphs, and each is appropriate for different types of data. What type of graph
would be most appropriate to make with these data? A line graph is very useful for
examining the relationship between two continuous variables.
•
Bar graphs - suitable for when you have a categorical independent and continuous dependent
variable. Used to make comparisons among groups.
•
Histograms - suitable for showing the distribution of continuous data. Breaks data into equal
intervals.
•
Line graphs - suitable for when you have continuous independent and dependent variables, like
changes over time. Used to look at trends.
•
Pie graphs - suitable for showing data that are parts of a whole.
Data Nuggets developed by Michigan State University fellows in the NSF BEACON and GK-12 programs
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Name_________________
Teacher Copy, Level 2
Draw your graphs below: Identify any changes, trends, or differences you see in your
graphs. Draw arrows pointing out what you see, and write one sentence describing what
you see next to each arrow.
•
•
Female Preference Score
•
There is a positive slope on both graphs.
In the first graph, no males had a red throat that received a score
lower than 3 or higher than 8.
In the second graph, most males performed 0-2 behaviors per minute,
and only a few performed more.
The most behaviors per minute were by males #23 and #24 who
performed almost 13 zig-zag dances per minute! These two males were
highly preferred by females.
Many males had a female preference score of 0 and were unable to
attract a mate.
3
2
1
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13
Male Courtship Behavior (#/minute)
Female Preference Score
•
•
3
2
1
0
0
2
4
6
8
10
Data Nuggets developed by Michigan State University fellows in the NSF BEACON and GK-12 programs
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Redness of Male Throat
Teacher Copy, Level 2
Name_________________
Teacher Note: To answer the scientific questions in this Data Nugget, students should
graph the relationship between (a) male throat redness and female preference and (b) male
courtship behaviors and female preference. They will have to select the appropriate data
from a table with extra variables that are not needed to answer the questions.
The line of best fit is included in the teacher guide but not on the student copies. You can
have students add a line of best fit to their graphs to assist in the visualization of the trend.
This can be done simply by eye using a ruler to draw a line through the center of the cloud of
points. If your students are more familiar with regression lines and associated statistics, they
could use Microsoft Excel on a computer to calculate the slope of this line for them or
perform a regression and calculate r2 and a p-value. However, because the trend in these
data is very clear, hand drawing the line should be sufficient.
Interpret the data:
Make a claim that answers each of the scientific questions.
Throat redness and courtship behaviors positively influence
female choice. Females preferred males with redder throats and
who performed more courtship behaviors (zig-zag dances) per
minute.
What evidence was used to write your claim? Reference specific parts of the table or
graphs.
There was a positive relationship between male throat color and
female preference, meaning that females chose males with redder
throats. Females did not prefer males with throats that were not
very red (i.e., redness of male throat score less than 5-6).
However, females did not prefer ALL males with a high redness of
throat score. There are many males with the high redness of
throat scores (6-8) that had zero or low female preference of
(i.e., scores of 2 or lower).
There was also a positive relationship between male courtship
behavior and female preference score. This means that females
preferred males that did more zig-zag dances. All males that had
a preference score of 0 performed fewer than 2 dances per
minute, on average.
Explain your reasoning and why the evidence supports your claim. Connect the data
back to what you learned about how female stickleback fish choose their mates.
Females prefer males who perform more display zig-zag dances per
minute. There is a positive relationship between male courtship
behavior and female preference in mating. Females also prefer
males with redder throats. There is a positive relationship
between male throat color and female preference in mating.
Data Nuggets developed by Michigan State University fellows in the NSF BEACON and GK-12 programs
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Teacher Copy, Level 2
Name_________________
Did the data support one, both, or neither of Alycia’s two alternative hypotheses? Use
evidence to explain why or why not. If you feel the data were inconclusive, explain why.
The data supports both hypotheses – in this system, females use
both male courtship behavior and throat color to determine their
mating preferences. Females preferred males with redder throats
and males who performed more zig-zag dances per minute.
Your next steps as a scientist: Science is an ongoing process. What new question do
you think should be investigated? What future data should be collected to answer your
question?
This was only the first step in determining the male traits that
females use to determine their mate choice. Here we looked at
whether female preference has a relationship with male courtship
behavior and throat redness. In later analyses, we also found
that competition between males and limited numbers of
territories means that not all males will have access to mate
with females.
Teacher Note: Student responses may vary, and they will probably generate a wide
diversity of questions for this system. You can have a class discussion where you jot down
all the questions on the board. Be prepared to ask your students to clarify or justify another
student's response in a class discussion. Do students see any ways to improve each
other's questions? Are some questions untestable? Remember, if your class wants to send
their questions about the study system to Alycia, the scientist studying sticklebacks, they
can email them to [email protected].
Data Nuggets developed by Michigan State University fellows in the NSF BEACON and GK-12 programs
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Teacher Copy, Level 2
Name_________________
Teacher Note: This activity can be used to stimulate a classroom discussion on the issue of
correlation versus causation. With her experimental design, Alycia found that male
sticklebacks with redder throats and who performed more zig-zag courtship dances per
minute were preferred by females. This is supported by the positive correlation between the
independent variables (redness of male throat and male courtship behavior) and the
dependent variable (female preference). However, correlations do not imply causation. Just
because Alycia found a correlation between female preference and the two male traits does
not mean that these male traits directly caused the differences in female preference.
Perhaps there is some other unmeasured male trait that is correlated with one of the
measured traits and is actually responsible for the trend in the data. Perhaps males with
redder throats also perform more zig-zag dances per minute, and females actually only
prefer one of these traits. The design of this study was a great first step but does not allow
Alycia to test for causation.
To determine if male courtship behavior and throat redness are correlated, students can
graph these data and draw a line of best fit. We have provided you with the r2, which is close
to 0, meaning that there is a very weak correlation between these two variables.
For more information, refer to regression teaching materials posted on our Resources page.
These materials guide students through calculating the slope and a correlation coefficient (r)
and performing statistics to see if the slope is significantly greater than zero.
• http://datanuggets.org/wp-content/uploads/2014/03/Student-Guide-for-RegressionAnalysis.pdf
• http://www.hhmi.org/biointeractive/teacher-guide-math-and-statistics
Data Nuggets developed by Michigan State University fellows in the NSF BEACON and GK-12 programs
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Teacher Copy, Level 2
Name_________________
Teacher Note: After students have completed this activity, you may want to finish with a
classroom discussion where students apply this research to a new biological context. Ask
students why they think there was such a range in the colorfulness of male throats (from 3 to
8 on the male throat redness scale) and in the amount of zig-zag dances they performed (0
to 12.93 dances per minute). What are possible advantages and disadvantages for having
colorful (high numbers) or non-colorful (low numbers) throats in this system? What are the
advantages or disadvantages of performing many or few dances in a minute? Hint:
Tradeoffs may maintain variation in these traits in the population. Prompt students to
consider the tradeoff between attracting mates while also making yourself more conspicuous
to predators. You may also prompt students to think about the investment that an individual
male fish has to make in these traits. Performing many dances may tire the male out, or take
away time he needs to perform other actions, like finding food. Making the red throat color
may be physiologically costly and require resources.
Have students consider two different hypothetical stickleback populations. One population
lives in a lake with no predators, while the other population lives in a lake with a species of
large fish that prey on sticklebacks. Would you expect there to be differences in throat
redness and courtship behaviors in these two environments? Might there be more or less
variation in these traits in one of the environments? Why or why not?
Additional teacher resources related to this Data Nugget:
Alycia’s blog post for BEACON on her stickleback work, “Making and Breaking a Species”
http://beacon-center.org/blog/2013/02/04/beacon-researchers-atwork-making-and-breaking-species/
Alycia’s blog post for the MSU museum:
http://museum.msu.edu/exhibitions/virtual/ssgallerysheets/2I2.html
Data Nuggets developed by Michigan State University fellows in the NSF BEACON and GK-12 programs
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