Animal Behavior Male ostriches compete for females by flapping their large wings and making hissing...
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Transcript of Animal Behavior Male ostriches compete for females by flapping their large wings and making hissing...
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 behaviorlearned behavior
• Biologists define behaviorbehavior 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 stimulusstimulus (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 responseresponse
• 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 The brain and other parts of the nervous system process the
information and direct the body's responseinformation 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 If disturbed, the moth will move its front wings to move its front wings to expose a striking circular expose a striking circular pattern on its hind wingspattern on its hind wings
• As one scientist has suggested, this behavior may this behavior may scare off predators when scare off predators when they mistake the moth's they mistake the moth's hind-wing pattern for the hind-wing pattern for the eyes of predatory owlseyes 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 Many behaviors are also influenced by genesgenes
• Therefore, some behaviors can be inherited by an animal's offspring
• Behaviors, like physical characteristics, Behaviors, like physical characteristics, may evolve under the influence of natural may evolve under the influence of natural selectionselection
• 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 After natural selection has operated for many generations, most individuals in the many generations, most individuals in the population will exhibit the adaptive population will exhibit the adaptive behaviorbehavior
Wing-Lifting Behavior
InnateInnate 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 behaviorinnate behavior, also called an
instinct, or inborn behavior• Innate behaviorsInnate 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 Biologists do not yet fully understand just how these kinds of interactions occurinteractions 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 learninglearning
• Acquired behavior is another name for Acquired behavior is another name for learninglearning, 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:• HabituationHabituation• Classical conditioningClassical conditioning• Operant conditioningOperant conditioning• Insight learning Insight learning
Habituation
• The simplest type of learning is habituation
• HabituationHabituation 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 When the worm has learned that the shadow is neither food nor threat, it will stop is neither food nor threat, it will stop respondingresponding– At this point the worm has habituated to the At this point the worm has habituated to the
stimulusstimulus
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 conditioningclassical 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 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 associates the stimuli of the sight and scent of the skunk with the punishment of its foul spray punishment of its foul spray
Operant Conditioning
• Conditioning is often used to train animals• Operant conditioningOperant conditioning occurs when an animal occurs when an animal
learns to behave in a certain way through learns to behave in a certain way through repeated practice, in order to receive a repeated practice, in order to receive a reward or avoid punishmentreward or avoid punishment
• Operant conditioning is also called trial-and-error 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 insight learninglearning, or reasoning
• Insight learning occurs when an animal applies Insight learning occurs when an animal applies something it has already learned to a new situation, something it has already learned to a new situation, without a period of trial and errorwithout 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 Insight learning is common among humans and other primatesprimates
• 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 imprintingimprinting
• 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 The young animal must learn from experience what object to followwhat 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 imprint on the odor of the stream in which they hatchthey 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 These behaviors are patterns that have evolved in elephantselephants
• 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 Night follows day, seasons change, the moon has
phases, the tides rise and fallphases, 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 migrationmigration, 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 Like many animals, sea turtles migrate in turtles migrate in response to seasonal response to seasonal changes in their changes in their environmentenvironment
Turtle Migration
Behavioral Cycles
• Behavioral cycles that occur in daily patterns are called circadian rhythmscircadian 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 courtshipcourtship, 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 ritualsrituals– A ritualritual 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 societiessocieties
• An animal societyAn 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 Therefore, helping a relative survive increases the
chance that the genes an individual shares with that chance that the genes an individual shares with that relative will be passed along to offspringrelative will be passed along to offspring
• Thus, social behavior that helps a relative Thus, social behavior that helps a relative survive and reproduce improves an survive and reproduce improves an individual's evolutionary fitness 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 territoryterritory, 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 If a rival enters a territory, the “owner” of the territory may attack the rival and drive it awayrival 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 competition occursoccurs
• 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 communicationcommunication—the passing of information from one organism to another—is involved
• Animals may use visual, sound, touch, or Animals may use visual, sound, touch, or chemical signals to communicate with one chemical signals to communicate with one anotheranother– 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 pheromonespheromones, 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 soundcommunicate 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
• LanguageLanguage is a system of communication that is a system of communication that combines sounds, symbols, or gestures according combines sounds, symbols, or gestures according to sets of rules about word order and meaning, such to sets of rules about word order and meaning, such as grammar and syntaxas 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 languageOnly humans are known to use language