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Chapter 27: Animal Behavior
KEY CONCEPT
Behavior lets organisms respond rapidly and
adaptively to their environment. Usually in a beneficial
way.
Examples?
Plant bends
toward light
Cat comes
when you
use a can
opener
Pufferfish inflates
when threatened
Toad releases
poison when
grabbed
Chapter 27: Animal Behavior
Behavioral responses to stimuli may be adaptive.
• Detecting and responding to stimuli is key to an individual’s
survival.
• Internal stimuli tell an animal what is occurring in its own
body.
– hunger
– thirst
– pain
Chapter 27: Animal Behavior
• External stimuli give an animal information about its
surroundings.
– sound
– sight
– changes in day length or temperature
Chapter 27: Animal Behavior
• Specialized cells that are sensitive to stimuli detect sensory
information.
– information is transferred to the nervous system
– nervous system may activate other systems in response
• Animal behaviors help to maintain homeostasis.
Chapter 27: Animal Behavior
• Kinesis and taxis are two types of movement-related
behaviors.
– Kinesis is an increase in random movement.
Example: Pill bugs increase activity as they dry out to find moist
areas
– Taxis is movement in a particular direction either
toward or away from a stimuli
–Example: plants growing toward light, deer running
away from rustling in the brush
Chapter 27: Animal Behavior
Internal and external stimuli usually interact to trigger
specific behaviors.
• Most behaviors are a response to both internal and external
stimuli
– Combination, not just one stimuli
• External stimuli may trigger internal stimuli.
• Green anole reproductive behavior is triggered by internal
and external stimuli.
– External: males become aggressive and court females
– Internal: females release hormones that make females
receptive
• How could internal and external stimuli cause you to wake
up in the morning?
Chapter 27: Animal Behavior
Some behaviors occur in cycles.
• A circadian rhythm is the daily cycle of activity.
– occurs over 24-hour period
– run by a biological clock
Chapter 27: Animal Behavior
• Behaviors may occur daily, monthly, seasonally, or annually.
– During hibernation, an animal enters a seasonal dormant
state.
What kind of stimuli might trigger hibernation?
Chapter 27: Animal Behavior
• Behaviors may occur daily, monthly, seasonally, or annually.
– During hibernation, an animal enters a seasonal dormant
state.
– During migration, animals move seasonally from one
portion of their range to another.
What kind of stimuli might trigger migration?
Chapter 27: Animal Behavior
• Circadian Rhythms survey
Chapter 27: Animal Behavior
KEY CONCEPT
Nature vs. Nurture Debate
Both genes and environment affect an animal’s behavior.
Chapter 27: Animal Behavior
Innate behaviors are triggered by specific internal and
external stimuli.
• An instinct is a complex inborn behavior.
• Instinctive behaviors share
several characteristics.
– innate, or performed
correctly the first time
– relatively inflexible
– Why would instincts be necessary?
– Baby Swimming Reflex
Chapter 27: Animal Behavior
• Many innate behaviors are triggered by a releaser.
– releaser is a simple signal
– herring gulls chicks and red
dot releaser
– environmental factors can
affect innate behaviors
– Ex: Honey Bees
Chapter 27: Animal Behavior
Many behaviors have both innate and learned
components.
• Learning takes many forms.
• Habituation occurs
when an animal
learns to ignore a
repeated stimulus.
• Imprinting is a rapid
and irreversible
learning process.
– critical period
Why might this person
– Konrad Lorenz
be wearing this
and graylag
costume?
geese
Chapter 27: Animal Behavior
• In imitation, animals learn by observing the behaviors of
others.
– young male songbirds
learn songs by listening
to adult males
– Children learning to talk
– snow monkeys and
potato-washing
behavior…younger
teaches older
Chapter 27: Animal Behavior
Learning is adaptive.
• Animals that can learn can better adapt to new situations.
• In associative learning, a specific action is associated with
its consequences.
– Child with a hot stove
– Birds with bad-tasting food
• Conditioning is one type of associative learning.
Chapter 27: Animal Behavior
• There are two types of conditioning.
– Classical conditioning: previously neutral stimulus
associated with behavior triggered by different stimulus
– Ivan Pavlov and salivating dog
Chapter 27: Animal Behavior
• There are two types of conditioning.
– Operant conditioning: behavior increased or decreased
by positive or negative reinforcement
– B.F. Skinner and “Skinner boxes”
Chapter 27: Animal Behavior
KEY CONCEPT
Every behavior has costs and benefits.
Chapter 27: Animal Behavior
Even beneficial behaviors have associated costs.
• The benefits of a behavior are increased survivorship (# of
individuals that survive from one year to the next) and
reproduction rates.
– both increase an individual’s fitness; favored by natural
selection
– both have costs
Chapter 27: Animal Behavior
• Behavioral costs can be divided into three categories.
– energy costs: energy not available for other tasks
– opportunity costs: time spent cannot be used on another
task
– risk costs: need food but risk getting eaten
Some
behaviors
seem
harmful but
are
beneficial
Chapter 27: Animal Behavior
Animals perform behaviors whose benefits outweigh their
costs.
• Behaviors evolve only if they improve fitness.
• Territoriality refers to the control of a specific area.
Chapter 27: Animal Behavior
• Optimal foraging states that natural selection favors
behaviors that get animals the most calories for the cost.
Ex: Oystercatchers eat
mussels…too big and
it takes too long and
too much energy to
open, too small and
there’s not enough
meat, so the most
successful eat the
medium mussels
Chapter 27: Animal Behavior
KEY CONCEPT
Social behaviors enhance the benefits of living in a
group.
If you had a choice would you rather live alone or in a
group? Why do you think humans live in groups?
Chapter 27: Animal Behavior
Living in groups also has benefits and costs.
• Social behaviors evolve when the benefits of group living
outweigh its costs.
– benefits: improved
foraging, reproductive
assistance, reduced
predation
– costs: increased
visibility, competition,
disease contraction
• Group living requires learning social structure and
membership.
Chapter 27: Animal Behavior
Social behaviors are interactions between members of the
same or different species.
• Animals use communication to keep in contact.
– Visual: gestures or postures
– Sound: Calls of alarm, distress, mating, etc.
– Touch: antennae
– Chemical: pheromones
Chapter 27: Animal Behavior
• Courtship displays are used to evaluate the fitness of a
potential mate.
• Defensive behaviors are used to protect the individual
and/or the group.
Chapter 27: Animal Behavior
Some behaviors benefit other group members at a cost to
the individual performing them.
• There are many types of helpful social behavior.
– cooperation
– reciprocity
– altruism
Chapter 27: Animal Behavior
• In altruism, an individual reduces its own fitness to help
other members of its social group.
– inclusive fitness: total # of genes contributed by relatives
to next generation
– kin selection: natural selection acts on survival of close
relatives
Chapter 27: Animal Behavior
Eusocial behavior is an example of extreme altruism.
• Eusocial species live in large groups of mostly
nonreproductive individuals.
– haplodiploid species: sex determined by # of
chromosomes, social insects (wasps, bees, ants)
Queen
Minor worker
Major worker
– diploid species: termites, snapping shrimp, naked mole
rats
• Eusocial behaviors likely evolve by kin selection.
Chapter 27: Animal Behavior
KEY CONCEPT
Some animals other than humans exhibit behaviors
requiring complex cognitive abilities.
Chapter 27: Animal Behavior
Animal intelligence is difficult to define.
• Cognition is the mental process of knowing through
perception or reasoning.
– awareness
– ability to judge
– ability to solve complex
problems
• Other factors affecting an
animal’s behavior may seem
like cognition.
– Clever Hans
Chapter 27: Animal Behavior
Some animals can solve problems.
• Insight is the ability to solve a problem mentally without
repeated trial and error.
– observed in primates, dolphins, and corvids
– chimpanzee retrieving hanging bananas
Chapter 27: Animal Behavior
• Tool use helps an animal accomplish a task.
– some dolphins use sponges to protect and hunt
– crows and chimpanzees make probing sticks
– capuchin monkeys use rocks to crack nuts
Chapter 27: Animal Behavior
Cognitive ability may provide an adaptive advantage for
living in social groups.
• Intelligence in animals seems to be correlated with two
characteristics.
– relatively large brains for their body size
– live in complex social groups
Chapter 27: Animal Behavior
• Cultural behavior spreads through a population by learning,
not by selection.
– taught to one generation by another
– aided by living in close proximity