Lecture 2 Methods of Behavioral Ecology.pptx

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Writing Assignment 1
Writing Assignment 1
Writing Assignment #1
Due Wednesday October 15th at the beginning of lecture
Writing Assignment #1
Due Wednesday, October 15th at beginning of lecture
To read:
A Tephritid Fly Mimics the Territorial Displays of its Jumping Spider Predators
Erick Greene; Larry J. Orsak; Douglas W. Whitman
To write:
Discuss how behaviors can evolve via natural selection. Use the two papers
as a focus for your discussion, but you can also draw upon examples from
class. Be sure to answer all of the following questions in your paper.
What three things are needed for a behavior to evolve via natural
selection? How can researchers test for each of these three
requirements? What were the predictions/hypotheses about the expected
outcome of natural selection that were made in each of the two papers?
What were the selective forces in nature or the lab? What kinds of
controls did the researchers use in their experiments to determine if a
behavior has evolved according to a particular hypothesis?
Alternative Male Strategies: Genetic Differences in Crickets
Author(s): William H. Cade
Assignment can be found on the class website. Please note the clarifications about
the graphs for the second paper.
Course Website:
http://bio.research.ucsc.edu/~barrylab/Ammon/behavioral_ecology/
Please write an essay about the topic. Do not simply answer the questions
above, because the questions are meant to give you ideas about how to
phrase your answer. Instead, imagine that you are a reporter, and you
have to write a story about how natural selection can affect behavior. As
part of your report, you have read the two assigned papers and are using
them to describe the latest evidence.
Niko Tinbergen s Four Questions
(Mnemonic for Tinbergen s Questions)
A – Animal
B – Behavior
C – Causation (Proximate)
D – Development (Proximate)
E – Evolution (Ultimate)
F – Function (Ultimate)
How to test hypotheses in behavioral ecology
1. Scientific method
2. Examples of how the founders of behavioral ecology tested
hypotheses.
3. Other examples of tests in behavioral ecology
Proximate Factors: What are the mechanisms involved?
Genetics, Developmental biology, Neuroscience, Endocrinology,
etc.
Ultimate Questions: Why did the behavior evolve?
Evolution and ecology
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The Nature of Science
The real scientific method
•  The purpose of science is to learn about our universe.
2. Science relies on evidence from the natural world and the
evidence is interpreted through logic.
3. Scientific claims are based on testing explanations against
observations of the natural world and rejecting the ones that fail
the test.
•  Scientific claims are subject to peer review and replication.
(Want theories that are useful and predictive.)
5. Theories are not absolutely proven. However, science corrects
itself and theories become more reliable.
http://undsci.berkeley.edu/article/0_0_0/howscienceworks_01
The real scientific method
Carl Sagan s tools for skeptical thinking
•  Independent confirmation (replication) of the facts.
2. Test more than one hypothesis.
3. Try not to get attached to a hypothesis because it is yours.
•  Quantify: Makes it is easier to discriminate among hypothesis.
•  In a chain of argument, all links (including the premise) must
work.
•  Occam s Razor: When two hypotheses fit the data equally well,
choose the simpler.
•  Always ask if the hypothesis can be falsified.
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4.  Arguments from authority carry little weight.
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The Nobel Prize in Physiology or Medicine 1973
Tinbergen and the Beewolf
Nikolaas Tinbergen (1907-1988)
• Formally developed Ethology
• Studied the survival value of behavior in black-headed
gulls.
Konrad Lorenz (1903-1989)
•Studied imprinting (Geese)
•Studied social behaviors
•Wrote King Solomon s Ring
Karl Von Frisch (1886-1982)
•Decoded bee language
Tinbergen and the Beewolf
How do beewolves find their homes among so many nest in the
dunes?
Proximate question
Hypothesis 1: The wasps actually took in the features of the
burrow s surroundings while circling above.
Tinbergen and the Beewolf
Hypothesis 2: If a wasp used landmarks it should be possible to do
more than merely disturb her by throwing her beacons all over
the place; I ought to be able to mislead her, to make her go to the
wrong place, by moving the whole constellation of her landmarks
over a certain distance.
Test 2a: Moved all landmarks one foot to the southeast.
Test 1: Swept areas around the burrows clean of landmarks.
Result 2a: The wasp female landed 1 ft to the southeast of her nest.
Result 1: Wasps stopped 4 feet in air from nests as if confused.
Repeated the approach again and again.
Dropped prey and searched randomly on the ground.
Test 2b: Moved landmarks back.
Result 2b: Wasp came directly back to her nest.
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Tinbergen and the Beewolf
Tinbergen and the Black-Headed Gulls
Hypothesis 3: Wasps could be trained to new landmarks.
Test 3: Put rings of pinecones around nests. Two days later, moved
the circle of pinecones.
Result 3. Wasps landed within the circle of pinecones, rather than
at their nests.
Tinbergen and the Black-Headed Gulls
Why do black-headed gulls remove broken eggshells from the nest
after the chick hatch?
Ultimate question
Hypothesis: It evolved because gulls with the behavior gained
reproductive success. Removing eggshells eliminates visual
cues that could give the nest away to predators.
Tinbergen and the Black-Headed Gulls
Eggs
taken by
Distance from
eggshell to egg (cm) crows
Eggs not
taken by
crows
Percentage
Eaten
15
63
87
42
100
48
102
32
200
31
118
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Prediction: The presence of broken eggshells should help predators
locate food.
Test: Took intact gull eggs and placed them around the sand dunes.
Placed broken egg shells at different distances away from the
eggs.
Result: Eggs closest to white eggshell bits were more likely to be
eaten by crows.
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Karl Von Frisch and the Bees
Karl Von Frisch and the Bees
Hypothesis: Bees can communicate information about distance.
Distance to feeding place (m)
Result: Longer distances correspond to longer waggle dances.
Bee video
Karl Von Frisch and the Bees
Karl Von Frisch and the Bees
Hypothesis: Bees can take in information about the direction of a
food source.
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Konrad Lorenz and Social Bonds in Birds
Overview on how to test hypotheses
•  Observations: observe behavioral interactions, observe genetic
relatedness, observe the context of the behavior, etc.
2. Experiments: allow controlled manipulation of the factors
involved in a behavior.
•  Comparative Method: Observe the results of natural experiments
conducted over evolutionary time
Konrad Lorenz
Hypothesis 1: Imprinting is the result of an instinct. That is, a
genetically predetermined response that is "released" by a
limited set of stimuli from the environment.
•  Modeling: Clarify thought about how the world works, can allow
testable predictions.
Hypothesis 2: Imprinting occurs during a "critical period" = a
limited time in an animal s early life.
Overview on how to test hypotheses
•  Comparative Method: Observe the results of natural experiments
conducted over evolutionary time
a. Example: Differences in social organization of weaver birds.
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Comparisons among species of weaver birds
•  Comparative Method: Observe the results of natural experiments
conducted over evolutionary time
a. Example: Differences in social organization of weaver birds.
Comparisons among species of weaver birds
John Crook s Hypotheses
1. Insect food in the forest is dispersed so birds feed solitarily and
defend territories to monopolize scattered resources. Both
parents need to provide parental care.
2. Seeds in the savannah are patchily distributed but locally very
abundant. Groups can cover a wider area to search for food and
food many not be limiting when a supply is found. Nests cannot
be hidden in open areas so are put in protected areas like acacia
trees, which may be limited in number. Large nests may also
provide thermal insulation. Food is abundant so females can
raise offspring alone. Males may therefore be able to spend time
attracting other mates.
From Krebs, Davies and West, 2012
3. Seeds in grasslands are patchy, so groups are favored. Nests
are vulnerable in open areas, which favors spacing them out.
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Overview on how to test hypotheses
•  Observations: observe behavioral interactions, observe genetic
relatedness, observe the context of the behavior, etc.
2. Experiments: allow controlled manipulation of the factors
involved in a behavior.
•  Comparative Method: Observe the results of natural experiments
conducted over evolutionary time
•  Modeling: Clarify thought about how the world works, can allow
testable predictions.
Goals for the class
1. Gain an understanding of the theories that have been used to
understand behavior.
2. Learn examples of how those theories have been tested. It is
important to know the evidence that shows that the theories are
useful and predictive.
3. Understand ways in which hypotheses about behavior can be
rigorously tested.
4. Learn that many alternative hypotheses may need to be tested
because different mechanisms can lead to similar outcomes.
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