Download Chapter 32: Animal Behavior - Johnston Community College

Chapter 32: Animal Behavior
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Genetic Basis of Behavior
The behavior of animals is any action
that can be observed and described.
All behavior has a genetic basis, as
demonstrated by various experiments.
Lovebirds are small green and pink
African parrots; several closely related
species differ by the way they build
nests.
Hybrids between species have trouble
with carrying nest materials.
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Nest-building behavior in
lovebirds
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Several experiments have been done
with the garter snake, which has two
different populations in California.
Inland populations are aquatic and feed
underwater on frogs and fish.
Coastal populations are terrestrial and
feed mainly on slugs.
In the lab, inland garter snakes refused to
eat slugs but coastal snakes ate them.
Hybrid offspring showed an intermediate
acceptance of slugs as food.
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Feeding behavior in garter
snakes
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Both the nervous and endocrine systems
are responsible for the integration of
body systems.
To test whether the endocrine system
influenced behavior, the egg-laying
behavior of a marine snail Aplysia was
examined.
Egg-laying hormone (ELH) causes the
snails to lay eggs even without mating.
ELH is thought to control the egg-laying
behavior in Aplysia.
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Development of Behavior
Some behaviors seem to be fixed action
patterns (FAPs) in which a specific cue
sets the behavior in motion.
Experiments with laughing gull chicks
show that improvement in motor skills,
as well as visual experience, strongly
affect development of chick begging
behavior.
This suggests that learning, rather than
FAPs, may be involved in gull chicks.
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Pecking behavior in laughing
gulls
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The Phenomenon of Learning
Operant Conditioning and Imprinting
Operant conditioning, one of many forms
of learning, is the gradual strengthening
of stimulus-response (behavior-reward)
connections.
Imprinting is another form of learning;
chicks, ducklings, and goslings will
follow the first moving object they see
during a sensitive period after hatching.
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Song-Learning in Birds
Song learning in birds is an active area of
research.
White-crowned sparrows sing a speciesspecific song, but males of a particular
region have their own dialect; birds
were caged into three groups to see
how young birds learn to sing from
older members of their species.
Birds in the first group heard no singing;
when grown, these birds sang a song
that was not fully developed.
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Birds in the second group heard tapes of
white-crowns singing; when grown, they
sang in a dialect, as long as the tapes
had been played during a sensitive
period.
Birds in the third group were given an
adult tutor; these birds sang a song of
even a different species, no matter when
the tutoring began.
It appears that social influence, along with
genetics, is of great importance in the
development of singing.
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Song-learning by white-crowned
sparrows
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Adaptiveness of Behavior
Since genes influence the development
of behavior, it can be assumed that
behavioral traits are among those
subject to natural selection.
Investigators studying survival value of a
given behavior seek to discover how a
given trait might improve reproductive
success.
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Males can father many offspring because
they produce sperm in great quantity; it
would be expected that they inseminate
as many females as possible.
Females produce few eggs, so choice of
mate becomes an important
consideration.
Experiments with satin bowerbirds and
birds of paradise support these bases
for sexual selection.
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Mating behavior in birds of
paradise
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Female Choice
Courtship displays are rituals that serve
to prepare the sexes for mating; they
help male and female recognize each
other so that mating will be successful.
Courtship displays also play a role in a
female’s choice of a mate.
Female choice can explain why male
birds are so much more showy than
females; colorful, lengthy plumes might
signify health and vigor.
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Male Competition
Evolution by sexual selection can occur
either when females have the
opportunity to select among potential
mates, and/or when males compete
among themselves for access to
reproductive females.
Only if the positive effects of male
competition outweigh the negative
effects will the animal have
reproductive success.
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Dominance Hierarchy
Male and female baboons within a troop
have separate dominance hierarchies
in which a higher-ranking animal has
greater access to resources than a
lower-ranking animal.
Dominant male baboons generally
monopolize females when they are
fertile, although males that help rear
offspring sometimes have breeding
access during less fertile times.
Dominance is decided by confrontations.
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A male olive baboon displaying
full threat
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Female choice and male
dominance among baboons
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Territoriality
A territory is an area that is defended
against competitors.
Territoriality includes the type of
defensive behavior needed to defend a
territory.
Vocalization and displays, rather than
outright fighting, may be sufficient to
defend a territory.
Red deer stags may actually lock antlers
and push against each other to repel
challengers.
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Competition between male red
deer
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Animal Societies
Some animals are solitary, others live in
small groups, and still others organize
a society in which members cooperate,
a behavior extending beyond mating
and parental care.
Social behavior in societies requires
communication between members.
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Communicative Behavior
Communication is an action by a sender
that affects the behavior of a receiver.
Chemical communication uses chemical
signals, such as pheromones; an
advantage is that this form of
communication works both night and
day.
Auditory (sound) communication is fast
and effective, and can be easily
modified.
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Use of a pheromone
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A chimpanzee with a researcher
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Visual communication involves signals
used by species active during the day.
For example, defense and courtship
displays are exaggerated and are always
performed in the same way so their
meaning is clear.
Tactile communication occurs when one
animal touches another.
Honeybees use a combination of methods
of communication, but especially tactile
ones, to impart information about food
distance and direction.
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Communication among bees
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Sociobiology and Animal
Behavior
Sociobiology applies the principles of
evolutionary biology to the study of social
behavior in animals.
It is assumed that a social individual
derives more reproductive benefits than
costs from living in a society.
Group living protects members from
predators and helps in finding food;
disadvantages include increased disease
and territoriality, and not all members of
the group will mate.
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Altruism Versus Self-Interest
Altruism is behavior that has the
potential to decrease the lifetime
reproductive success of the altruist
while benefiting the reproductive
success of another member of the
group.
Genetic relatedness appears to underlie
altruism; an altruistic act is best
targeted at a close relative sharing the
same genes.
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Direct selection is natural selection that can
result in adaptation to the environment
when the reproductive success of
individuals differs.
Indirect selection is natural selection that
can result in adaptation to the
environment when individuals differ in
their effects on the reproductive success
of relatives.
Inclusive fitness of an individual includes
personal reproduction and reproduction
of relatives.
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Inclusive fitness
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Inclusive fitness is measured by the
genes an individual contributes to the
next generation, either directly by
offspring or indirectly by way of
relatives.
Many of the behaviors once thought to be
altruistic turn out to be examples of
indirect selection and are adaptive.
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Chapter Summary
Various experiments with African
lovebirds, California garter snakes, and
and the marine snail Aplysia have
shown that behavior has a genetic
basis, and further that the nervous and
endocrine systems control behavior.
The environment influences the
development of behavioral responses,
and learning occurs.
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Song learning in birds involves various
elements, including a sensitive period
during which the bird is primed to learn,
and the effect of social interactions.
Since genes influence the development of
behavior, it can be assumed that
behavioral traits, such as mate choice,
are among those subject to natural
selection.
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Evolution by sexual selection can occur
either when females have the
opportunity to select among potential
mates, and/or when males compete
among themselves for access to
reproductive females.
Territoriality includes the type of
defensive behavior needed to defend a
territory.
Vocalization and displays, rather than
outright fighting, may be sufficient to
defend a territory.
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Animals that form social groups use
chemical, auditory, visual, or tactile
communication, and communication
fosters cooperation that benefits both
sender and receiver.
In most cases, individuals of a society act
to increase their own reproductive
success by helping relatives who share
their genes.
Altruistic behavior has a benefit in terms
of inclusive fitness.
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