Transcript Animal Behavior - Cloudfront.net

Animal Behavior
• Male ostriches
compete for females
by flapping their large
wings and making
hissing noises
Animal Behavior
Elements of Behavior
•
•
•
•
•
•
•
•
•
•
Do you wash your vegetables before you eat them?
If so, you have something in common with a troop of Japanese
macaque monkeys that live on the Pacific island of Koshima
Many years ago, biologists in Koshima began leaving sweet potatoes
on a sandy beach to entice the resident monkeys into the open
The monkeys ate their potatoes with sand still stuck to them
One day, a young female member of the troop dunked her potato into a
nearby pool and scrubbed the sand off it with her hand
The young monkey, apparently preferring to eat a washed potato, repeated
this technique each day
Soon, another monkey in the troop started to imitate her
Months later, her mother began to copy her, too
Eventually, all troop members came to wash their potatoes in the pool
To this day, the descendants of the monkeys on the island of Koshima wash
their sweet potatoes before eating them
Stimulus and Response
• The macaque monkeys you just read about were exhibiting a
learned behavior
• Biologists define behavior as the way an organism reacts to
changes in its internal condition or external environment
– A behavior can be simple, such as turning your head in the
direction of a noise, or complex, such as washing food
• Usually, behaviors are performed when an animal reacts to a
stimulus
– A stimulus (plural: stimuli) is any kind of signal that carries
information and can be detected
• If you are hungry, your body is providing you with an internal stimulus
that might prompt you to eat
• The sound of your phone ringing on a Friday night is an external
stimulus that might result in your running to answer it!
Stimulus and Response
• A single, specific reaction to a stimulus—
such as waking up when you hear an alarm—
is called a response
• A behavior may consist of more than one
response
– For example, a tiger shark might respond to the
movements of a potential prey by swimming toward
the stimulus, attacking the source of the
movement, and swallowing the prey
• What stimuli are you responding to right now?
Types of Stimuli
• Animals respond to many types of external stimuli,
such as light, sound, odors, and heat
– However, not every animal can detect all of these stimuli
• Humans perceive the world through many senses—
including sight, smell, touch, taste, and hearing
• Other animals have different senses and may
respond to stimuli that you are not equipped to
sense
– The Mexican bulldog bat, for instance, uses high-pitched
sounds, which humans cannot hear, to detect the ripples
made by a fish breaking the surface of a lake
– Some birds can detect Earth's magnetic field and use it to
navigate over complex terrain
How Animals Respond
• Because of the differences in animals' sensory abilities,
responses can vary greatly
• When an animal responds to a stimulus, body systems—
including the sense organs, nervous system, and muscles—
interact to produce the resultant behavior
• Once an animal's senses have detected an external stimulus,
that information is passed along nerve cells to the brain
– The brain and other parts of the nervous system process the
information and direct the body's response
• Animals with very simple nervous systems are capable of only
simple behaviors, such as moving toward a stimulus or away
from it
– For example, an earthworm will move away from bright light
• Animals with more complex nervous systems, such as frogs, are
better equipped to respond with more complicated and precise
behaviors
Wing-Lifting Behavior
• Moths of the genus Automeris
normally rest with their front
wings over their hind wings
• If disturbed, the moth will
move its front wings to
expose a striking circular
pattern on its hind wings
• As one scientist has
suggested, this behavior may
scare off predators when
they mistake the moth's
hind-wing pattern for the
eyes of predatory owls
Behavior and Evolution
•
•
•
•
•
•
Animal behavior is as important to
survival and reproduction as any
physical characteristic, such as teeth or
claws
– Recall that physical traits develop
according to a specific set of genetic
instructions
Many behaviors are also influenced by
genes
Therefore, some behaviors can be
inherited by an animal's offspring
Behaviors, like physical characteristics,
may evolve under the influence of natural
selection
A behavior that is directed by genes may
help an individual to survive and
reproduce
– For example, the genes that code for
behavior of the moth in the figure
may help the moth escape predators
– Organisms with an adaptive
behavior will survive and reproduce
better than organisms that lack the
behavior
After natural selection has operated for
many generations, most individuals in
the population will exhibit the adaptive
behavior
Wing-Lifting Behavior
Innate Behavior
• Why do newly hatched birds beg for food within moments after
hatching?
• How do spiders know how to build their first web?
• These animals are exhibiting an innate behavior, also called an
instinct, or inborn behavior
• Innate behaviors appear in fully functional form the first time
they are performed, even though the animal may have had no
previous experience with the stimuli to which it responds
– One of the simplest innate behaviors is the suckling of a newborn
mammal
– Other innate behaviors, such as the weaving of a spider web or the
building of hanging nests by weaver birds, can be quite complex
– All innate behaviors depend on internal mechanisms that develop
as a result of complex interactions between an animal's genes and
its environment
• Biologists do not yet fully understand just how these kinds of
interactions occur
Web Building
• Innate behaviors appear
in fully functional form
the first time they are
performed
• Because web building
is an innate behavior, a
spider weaves a web
correctly the first time it
performs the behavior
Web Building
Learned Behavior
• Animals often live in unpredictable
environments, so their behavior must be
flexible enough to deal with uncertainty and
change
– Many animals can alter their behavior as a result
of experience
– Such changes are called learning
• Acquired behavior is another name for
learning, because these behaviors develop
over time
Learned Behavior
• Many animals have the ability to learn
• Organisms with simple nervous systems, such as most
invertebrates, may learn only rarely
• Among a few invertebrates, and many chordates, learning is
common and occurs under a wide range of circumstances
• In animals that care for their young, for example, offspring can learn
behaviors from their parents or other caretakers
• Scientists have identified several different ways of learning:
– The four major types of learning are:
•
•
•
•
Habituation
Classical conditioning
Operant conditioning
Insight learning
Habituation
• The simplest type of learning is
habituation
• Habituation is a process by which an
animal decreases or stops its response
to a repetitive stimulus that neither
rewards nor harms the animal
• By ignoring a nonthreatening or
unrewarding stimulus, animals can spend
their time and energy more efficiently
Habituation
• Consider the common shore ragworm
– This animal lives in a sandy tube that it leaves
only to feed
– If a shadow passes overhead, the worm will
instantly retreat to the safety of its burrow
– Yet, if repeated shadows pass within a short time
span, this response quickly subsides
• When the worm has learned that the shadow
is neither food nor threat, it will stop
responding
– At this point the worm has habituated to the
stimulus
Classical Conditioning
• When a dog sees its owner approaching with a leash, it may
wag its tail and bark, eager to go for a walk
– The dog has learned to associate the sight of the leash with a walk
• Any time an animal makes a mental connection between a
stimulus and some kind of reward or punishment, it has
learned by classical conditioning
– In the case of the dog and its owner, the stimulus of the leash is
associated with a pleasant reward—a brisk walk
• Now, think of what happens if a dog tries to attack a skunk
• The skunk sprays the dog with a substance that stings and
smells awful
– In the future, that dog is likely to avoid skunks, because it
associates the stimuli of the sight and scent of the skunk with the
punishment of its foul spray
Operant Conditioning
• Conditioning is often used to train animals
• Operant conditioning occurs when an animal
learns to behave in a certain way through
repeated practice, in order to receive a
reward or avoid punishment
• Operant conditioning is also called trial-anderror learning because it begins with a
random behavior that is rewarded in an event
called a trial
– Most trials result in errors, but occasionally a trial will
lead to a reward or punishment
Operant Conditioning
• Operant conditioning was first described in the
1940s by the American psychologist B. F. Skinner
• Skinner invented a testing procedure that used a certain
type of box called a “Skinner box”
• A Skinner box contains a colored button or lever
that, when pressed, delivers a food reward
– After an animal is rewarded several times, it
learns that it gets food whenever it presses the
button or lever
– At this point, the animal has learned by operant
conditioning how to obtain food
Insight Learning
• The most complicated form of learning is insight
learning, or reasoning
• Insight learning occurs when an animal applies
something it has already learned to a new situation,
without a period of trial and error
– For instance, if you are given a new math problem on an
exam, you may apply principles you have already learned in
the class in order to solve the problem
– Insight learning is common among humans and other
primates
• In one experiment, a hungry chimpanzee used insight learning
to figure out how to reach a bunch of bananas hanging
overhead: it stacked some boxes on top of one another and
climbed to the top of the stack
• In contrast, if a dog accidentally wraps its leash around a tree,
the dog is usually unable to free itself
Instinct and Learning Combined
• Most behaviors result from a
combination of innate ability and
learning
– Young white-crowned sparrows, for example,
have an innate ability to recognize their own
species' song
– To sing the complete version, however, the
young birds must first hear it sung by the
adults
Instinct and Learning Combined
• Some very young animals, such as ducks
and geese, learn to recognize and follow the
first moving object that they see during a
critical time early in their lives
– Usually, this object is their mother
– This process is called imprinting
• Imprinting keeps young animals close to their mother,
who protects them and leads them to food sources
• Once imprinting has occurred, the behavior cannot be
changed
Instinct and Learning Combined
• Imprinting involves both innate and learned
behavior
– The young animals have an innate urge to follow the
first moving object they see, but they are not born
knowing what that object will look like
– The young animal must learn from experience
what object to follow
– In fact, the object on which the young animal imprints
does not have to be its mother, or even a living
organism
Instinct and Learning Combined
• Imprinting can occur through scent as
well as sight
– Newly hatched salmon, for example,
imprint on the odor of the stream in which
they hatch
• Young salmon then head out to sea
• Years later, when they mature, the salmon
remember the odor of their home stream and
return there to spawn
Patterns of Behavior
• At this very moment, somewhere in an African
grassland, elephants are calling to one another
• Elephants communicate with sounds that they use to
locate each other across distances more than 2
kilometers away
• When they are not calling long-distance, elephants may
spar with each other to test their strength or greet
each other by wrapping their trunks together
• These behaviors are patterns that have evolved in
elephants
• In this section, you will investigate some common
patterns of animal behavior
Behavioral Cycles
• The environment is full of natural cycles
– Night follows day, seasons change, the moon has
phases, the tides rise and fall
• Many animals respond to periodic changes
in the environment with daily or seasonal
cycles of behavior
– For example, several species of reptiles and
mammals are active during warm seasons but enter
into a sleeplike state, or dormancy, during cold
seasons
– Dormancy allows an animal to survive periods when
food and other resources may not be available
Behavioral Cycles
• Another type of behavior that is influenced
by changing seasons is migration, the
periodic movement from one place to
another and then back again
– Animals that migrate include species of birds,
butterflies, and whales
• Migration usually allows animals to take
advantage of favorable environmental
conditions
– For example, when birds fly south for the winter, they
go to regions where food is more plentiful than in
northern areas
Turtle Migration
• Each year, between
December and June,
green sea turtles
migrate from their
feeding grounds along
the coast of Brazil to
mate and nest on
Ascension, a tiny island
more than 2000
kilometers away
• Like many animals, sea
turtles migrate in
response to seasonal
changes in their
environment
Turtle Migration
Behavioral Cycles
• Behavioral cycles that occur in daily
patterns are called circadian rhythms
– The fact that you sleep at night and attend
school during the day is an example of a
circadian rhythm
Courtship
• Animal behavior is geared toward
reproduction as well as survival
– To pass along its genes to the next
generation, any animal that reproduces
sexually needs to locate and mate with
another member of its species at least
once
– Courtship behavior is part of an overall
reproductive strategy that helps many
animals identify healthy mates
Courtship
• In courtship, an individual sends out
stimuli—such as sounds, visual displays, or
chemicals—in order to attract a member of
the opposite sex
– For example, fireflies flash a distinct series of light
signals to indicate their readiness to mate
– The musical trill of a tree frog and the sheeplike bleat
of a narrowmouth toad are among the many
distinctive breeding calls of amphibians
Courtship
• In some species, courtship involves an elaborate
series of behaviors called rituals
– A ritual is a series of behaviors performed the
same way by all members of a population for the
purpose of communicating
• Most rituals consist of specific signals and
individual responses that continue until mating
occurs
– For example, newly paired cranes engage in
intense periods of dancing before they mate
Social Behavior
• Whenever animals interact with members of
their own species, as in courtship, they are
exhibiting social behavior
– Many animals go beyond courtship in their social
behavior and form societies
• An animal society is a group of related
animals of the same species that interact
closely and often cooperate with one another
– It takes the cooperative work of millions of
termites, for example, to build a single termite
mound
Social Behavior
• For some species, membership in a society
offers great survival advantages
– Zebras and other grazers, for example, band
together when grazing
• They are safer from predators when they are part of a group
rather than when they are alone
• Animal societies also use strength in
numbers to improve their ability to hunt, to
protect their territory, to guard their young,
and to fight with rivals if necessary
– In wild African dog packs, for instance, adult
females take turns guarding all the pups in the pack,
while the other adults hunt together for prey
Social Behavior
• Often, members of a society are closely
related to one another
– Related individuals share a large proportion of
each other's genes
• Therefore, helping a relative survive increases the
chance that the genes an individual shares with that
relative will be passed along to offspring
• Thus, social behavior that helps a relative
survive and reproduce improves an
individual's evolutionary fitness
Social Behavior
• Primates form some of the most complex
animal social groups known
• Macaque, baboon, and other primate
societies hunt together, travel in search of
new territory, and interact with neighboring
societies
• A great deal of what we know about primate
societies comes from the work of Jane Goodall,
the animal behaviorist, who spent thousands
of hours observing chimps in their natural
habitat
Competition and Aggression
• Some animals have behaviors that help prevent others from
using limited resources
– Often, such patterns involve a specific area, or territory, that is
occupied and protected by an animal or group of animals
• Territories contain resources, such as food, water, nesting
sites, shelter, and potential mates, that are necessary for an
animal's survival and reproduction
– By claiming a territory, an animal keeps others at a distance
• If a rival enters a territory, the “owner” of the territory may attack the
rival and drive it away
• Algae-eating damselfish are notorious for making such attacks
– An algae-eating damselfish can distinguish other algae-feeding
species from species that do not eat algae
– The damselfish chases the other algae-eaters away, but ignores
the fish that do not eat algae
Competition and Aggression
• When two or more animals try to claim limited
resources, such as a territory or food, competition
occurs
• Many animals, such as the giraffes, use rituals and
displays when they compete
• During competition, animals may also show aggression,
a threatening behavior that one animal uses to gain
control over another
– For instance, before a pride of lions settles down to eat,
individuals may snap, claw, and snarl at one another
– The most aggressive members will get to eat their fill of prey
– The less aggressive lions will have to wait for their chance
to feed
Giraffe Competition
• By interwining their
long necks, these two
giraffes compete for
resources on an
African savanna
• What resources might
these giraffes
compete for?
Giraffe Competition
Communication
• Often, when animal behavior involves more
than one individual, some form of
communication—the passing of information
from one organism to another—is involved
• Animals may use visual, sound, touch, or
chemical signals to communicate with one
another
– The specific techniques that animals use depend on
the types of stimuli their senses can detect
Visual Signals
• Animals with good eyesight often use visual
signals involving movement and color
• Cuttlefish, for example, have large eyes that
are as sophisticated as those of vertebrates
– In a matter of seconds, a single cuttlefish can
undergo changes in the colors and patterns on its
body
– Its skin will pucker into bumps and spines, then
suddenly become smooth as stone
– These visual displays—as fascinating as any
computer screen saver—function in defense, hunting,
mating, warning, and perhaps other forms of
communication that are not yet known
Chemical Signals
• Animals with well-developed senses of smell,
including insects, fishes, and many
mammals, may communicate with chemicals
• For example, some animals release
pheromones, chemical messengers that
affect the behavior of other individuals of the
same species, to mark a territory or to signal
their readiness to mate
Sound Signals
• Animals with strong vocal abilities, including
crickets, toads, and birds, communicate with sound
– Some animals that use sound have evolved elaborate
communication systems
• Dolphins, for example, rely mainly on sound signals in
the dark and often murky ocean depths where vision is
not very useful
– Scientists have discovered that bottlenose dolphins each
have their own unique “signature” whistle that is used for
recognition
– The dolphins' whistles function something like your
signature on a letter, letting others know who is sending the
communication
Language
• The most complicated form of communication is
language
• Language is a system of communication that
combines sounds, symbols, or gestures according
to sets of rules about word order and meaning, such
as grammar and syntax
– Many animals, like dolphins, elephants, and
gorillas, have fairly complex ways of
communicating
– However, outside of experiments in which they
were trained by humans, none of those animals
have been shown to use language
• Only humans are known to use language