Post on 28-Dec-2015
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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 ImprintingThese 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.
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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.
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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.
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http://www.awakeningpotentials.com/images/imprinting2.jpg
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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 signals2. 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 ForagingExample:
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 malesMales and femalesJust females
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Sexual SelectionThese 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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http://image16.webshots.com/16/1/42/94/183414294zHoflW_ph.jpg
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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 VariationDespite 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 ExampleThe 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 throatsBlue throatsYellow throats
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Game TheoryThe 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 yellowOrange defeats blueYellow 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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AltruismThe 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.
http://www.sciencecases.org/kin_selection/squirrels.jpg
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Inclusive FitnessInclusive 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 LearningIndividuals in a
population copy the mate choice of others.
A classic example of this involves guppies.
http://www.aquariumschatzberger.com/images/lebendgebaerende/15392_guppy-maennchen-rote.JPG
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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.