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Chapter 51
Behavioral Ecology
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Behavioral Ecology
The scientific observation of animal
behavior, what controls it, how it
develops, evolves, and contributes to
the reproductive success of an
organism.
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Behavioral Ecology
Understanding animal behavior is
important to conserving endangered
species and controlling the spread of
infectious diseases.
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Animal Behavior
There are two main classes of
questions that can be asked about
animal behavior:
1. Those that focus on immediate stimulus
and mechanism of behavior.
2. Those that explore how the behavior
contributes to the survival and reproductive
success.
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What Is Behavior?
It is a phenotype--a product of our
genes.
Behavior is everything an animal does,
and how it does it.
Behavior can also be learned.
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Proximate and Ultimate
Questions
The observation of behavior involves
proximate and ultimate questions.
Proximate questions focus on the stimulus
and what triggers the behavior.
Ultimate questions address the
evolutionary significance of a behavior.
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Proximate Questions
Again, these focus on the stimulus and
what triggers it.
Additionally, it seeks the genetic,
physiological, and anatomical
mechanisms underlying the behavior.
Most importantly: these are mechanism
and development questions.
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Ultimate Questions
Address evolutionary significance of
behavior.
They are often questions that propose a
hypothesis about an observed behavior.
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4 Questions For
Understanding Behavior
Proximate Questions (mechanism and
development):
1. What is the mechanistic basis for
behavior?
2. How does the development of the
animal from the zygote to the mature
individual influence behavior?
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4 Questions For
Understanding Behavior
Ultimate Questions (evolutionary):
3. What is the evolutionary history of the
behavior?
4. How does the behavior contribute to the
survival and reproductive fitness?
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Fixed Patterns and Imprinting
These are two behaviors frequently
studied by ethologists.
Fixed Action Pattern (FAP) is a
sequence of unlearned behaviors that
are essentially unchangable.
Once initiated, they are carried to
completion.
An FAP is triggered by an external
sensory stimulus called a sign stimulus.
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Niko Tinbergen
A classic example
of sign stimuli and
FAP’s:
3-spined male
stickleback fish.
QuickTime™ and a
TIFF (U ncompressed) decompressor
are needed to see this picture.
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Niko Tinbergen
These fish attack other males invading
their nesting area.
The stimulus comes from the red
underside of the intruder.
The stickleback won’t attack any fish
lacking a red-belly. Females don’t have
red bellies.
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Niko Tinbergen
The male sticklebacks will attack fake
models, unrealistic models, anything as
long as some red is present.
QuickTi me™ and a
TIFF (U ncompressed) decompressor
are needed to see this picture.
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Imprinting
Imprinting is a type of behavior that
involves both learning and innate
components which are generally
irreversible.
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Imprinting
The sensitive period of imprinting only
lasts a limited time, and is the only time
where certain behaviors can be learned.
During periods of bonding, young
imprint on their parents and learn the
basic behaviors of their species.
This is also the period of time where the
parents learn the appearance of their
offspring.
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Imprinting
If bonding doesn’t occur, death of the
offspring usually results.
How and on whom do the young know
to imprint?
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Imprinting
The tendency to respond is innate in the
birds.
The outside world provides an
imprinting stimulus, something to which
the response will be directed.
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Konrad Lorenz
Lorenz experimented with geese.
Extensive research shows that
behavioral traits are influenced by both
genetic and environmental components.
Just as much as are the anatomical and
physiological traits.
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Konrad Lorenz
In fact, Lorenz
showed that geese
(and other
nidifugous birds)
imprint on the first
moving stimulus
they see shortly
after their birth.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
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http://www.awakeningpotentials.com/images/imprinting2.jpg
Nature Vs. Nurture
This is not a debate in biology. The
question becomes: How do both the
genes and the environment influence
the development of phenotypes?
Behavior that is developmentally fixed is
called innate behavior (nature).
Behavior that is a result of the environment
is called learned behavior (nurture).
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Studying Nature Vs. Nurture-Movements
Many movements are under genetic
influence and are called “directed
movements.”
Kinesis is a simple change in activity or
turning rate in response to a stimulus.
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Kinesis Example:
Sow (pill) bugs survive best in moist environments.
They exhibit kinesis in response to variations in
humidity.
They become more active only in dry areas.
They are less active in moist areas.
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Kinesis
The sow bugs don’t move toward or away
from specific conditions.
Their increased movement in response to a
dry condition increases the likelihood they will
end up under a moist area.
When they reach a moist area, they slow
down, and this increases the likelihood they
will stay there.
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Taxis
Taxis is the movement toward or away
from a stimulus.
Positive-toward.
Negative-away.
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Studying Nature Vs. Nurture-Communication
Behavior can be controlled by signals
and responses.
The transmission of, reception of, and
response to signals constitute
communication.
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The Types of Animal Signals
There are two main types:
1. Chemical signals
2. Auditory signals
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Chemical Signals
Chemical signals and pheromones are
genetically controlled and elicit a
behavior in other animals.
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Auditory Signals
Some animals such as birds and
insects sing songs.
Others make noises with their body
parts. These songs are related to
courtship rituals and are under genetic
control (nature), learned control
(nurture), and/or both.
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Natural Selection
Natural selection favors behaviors that
increase survival and reproductive
success.
This can be observed in nature.
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Optimal Foraging
Optimal foraging behavior looks at the
process of hunting for food as a
compromise between the nutritional
benefits of gathering food and the
energy costs of obtaining food.
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Optimal Foraging
According to this theory, natural
selection favors the individuals that
utilize a foraging behavior that
minimizes energy costs while
maximizing energy output.
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Optimal Foraging
Example:
The energy cost-benefit of dropping
molluscs on the coastal rocks by
Northwestern crows.
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Sexual Selection
Recall that it is basically natural
selection for mating success. Mates are
chosen on the basis of their
characteristics.
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Sexual Selection
Determining the basis of sexual
selection in female zebra finches.
Females imprinted on their fathers, and
this was demonstrated by
experimenting with the young finches.
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Sexual Selection
Male zebra finches have a very
ornate head compared to female
finches.
On the heads of these birds
were taped red feathers.
Different nests were examined.
Only males
Males and females
Just females
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Sexual Selection
These feathers were
taped on before the
eyes of the young
were opened to
determine which sex
played a role in mate
preference.
The results were
compared to control
groups of offspring
whose parents had no
headdresses.
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Sexual Selection
When the chicks
matured, they were
given a variety of
mate choices.
Males had no
preference at all
toward ornamented
or non-ornamented
females.
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Sexual Selection
Females raised by
non-adorned
parents or females
with a headdress,
had no preference
between
ornamented or
non-ornamented
males.
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Sexual Selection
Females raised in
families with the male
having the red
headdress preferred
males with heads
having headdresses
suggesting females
imprint on their
fathers.
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Sexual Selection
These results also suggest that the
mate choice selection by females plays
a part in the evolution of ornamentation
in male zebra finches.
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Sexual Selection
There are also
forms of male
competition for
mates.
Male competition for
mates is a source of
intrasexual
competition that can
reduce variation.
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QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://image16.webshots.com/16/1/42/94/183414294zHoflW_ph.jpg
Agonistic Behavior
Agonistic behavior, for example, is a
ritualistic type of competition that
determines which competitors gain
access to a resource such as food or
mates.
The outcome can be determined by
strength, size, or in the form of horns,
teeth, etc.
They can be psychological in appearance.
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Preservation of Variation
Although the potential for reduced
variation is there, there also exists a
wide variety of individuals with a lot of
behavioral and morphological
adaptation.
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Preservation of Variation
Despite cases of reduced variation,
there are many species that maintain
variation.
Isopods that live within sponges are an
example.
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, , and Isopods
These genetically distinct males live
within sponges.
-males defend sponges against other males.
-males mimic the female morphology and
behavior. They get no response from males and have free access to the harem.
-males live within the harem.
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, , and Isopods’ Mating
Success
The mating success is dependent on the
densities of males and female living within
the sponges.
When one female lives in the sponge, the male fathers most of the offspring.
When there is more than one female, the male fathers 60% of the offspring.
As the harem size increases, the -male’s
reproductive rate increases.
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Conclusions
The information demonstrates that the
reproductive success among the three
different males is equal.
To explain the situation where natural
selection fails to exclude any one
variation (such as the one with the ,,
and isopods), scientists use what is
known as game theory.
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Game Theory
Game theory is used to explain the
preservation of variation in the face of
competition.
It evaluates the alternative strategies to
a situation where the mating outcome
depends on the strategies of all
individuals involved in the process.
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Game Theory: An Example
The explanation of three different male
phenotypes in populations of side
blotched lizards in the inner coastal
ranges of California.
There are 3 genetically controlled colors:
Orange throats
Blue throats
Yellow throats
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Game Theory
The frequencies of the individuals in
the general population fluctuate
between the 3 forms.
The relative mating success of these
three morphs changes over time.
It’s similar to rock, scissors, paper.
Blue defeats yellow
Orange defeats blue
Yellow defeats orange
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Game Theory
Blue defeats yellow because they
defend a smaller number of females in a
smaller area.
They can’t defend against the
aggressive orange.
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Game Theory
Orange moves in and defeats the less
aggressive blue lizard and takes over a
larger area with many females.
It now comes under attack from the
sneaky yellow.
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Game Theory
Due to the large number of females in
the orange lizard’s territory, he can’t
defend against the sneaky yellow lizard
who eventually takes over.
The cycle then repeats.
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Altruism
The selfless behavior of
some animals that reduces
their fitness, but increases
the overall fitness of the
population.
Example:
Belding’s ground squirrels
give a high pitched warning
signal but draw attention to
themselves.
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http://www.sciencecases.org/kin_selection/squirrels.jpg
Inclusive Fitness
Inclusive fitness helps to
explain altruism. Giving
off the warning signal
helps to preserve the
genes of the individual or
of its close relatives.
Protecting offspring in the
face of death helps to
increase their genetic
complement in the next
generation.
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Reciprocal Altruism
This is a case where an animal will act
altruistically toward another unrelated
animal.
It is relatively rare, and is often
observed in situations were the animals
are likely to meet again where the favor
can be returned.
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Reciprocal Altruism
It is a tit-for-tat strategy.
Cooperation is key.
U of M professors have studied it in
animals.
Non-cooperative animals bring on
retaliation until cooperation is reached.
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Social Learning
This is a way many animals learn
through observation of others.
The transfer of information through
social learning influences the behavior
of others.
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Mate Choice
Copying--A Form
of Social Learning
Individuals in a
population copy the
mate choice of
others.
A classic example of
this involves
guppies.
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http://www.aquariumschatzberger.com/images/lebendgebaerende/15392_guppy-maennchen-rote.JPG
Mate Choice Copying--Social
Learning
Female guppies in the wild
prefer to mate with males
showing a high percentage
of orange coloration.
They also copy the mate
choice of other females.
That is, they mate with
males that have been
successful at attracting
other females.
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Mate Choice Copying--Social
Learning
The experiment to
demonstrate mate choice
copying was as follows:
Female guppies were given
the choice of mating with
males of varying degrees of
orange coloration.
Females were also given the
choice between males with or
without other females
present.
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Mate Choice Copying--Social
Learning
When the same degree of coloration in
males was offered to females with
another female present and engaging in
a courtship ritual, the experimental
females chose the males with little
coloration.
They were copying the mate choice of the
other females.
This demonstrated social learning.
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Mate Choice Copying--Social
Learning
What this demonstrates:
Below a certain threshold of difference in
male coloration, mate choice copying will
mask the genetically controlled female
preference for orange males.
A female that mates with males that are
attractive to other females may increase the
probability that her male offspring will also
be attractive and have a high reproductive
success.
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