發育 (development) ─ 動物行為學 (ethology) 鄭先祐 (ayo) 國立 臺南大學...
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發育 (Development)
─ 動物行為學 (Ethology)
鄭先祐 (Ayo)
國立 臺南大學 環境與生態學院生態科學與技術學系 教授
Ayo NUTN Web: http://myweb.nutn.edu.tw/~hycheng/
大學部 生態學與保育生物學學程 ( 必選 ) 2010 年 秋冬
Ayo 教材 (動物行為學 2010) 2
Part 1. 動物行為的研究途徑 ( 個體行為 )
歷史背景 (History of the Study of Animal Behavior ).
基因分析 (Genetic Analysis of Behavior ). 天擇 (Natural Selection and Behavior ). 學習與認知 (Learning and Cognition.) 生理分析 (Physiological Analysis)
( 一 ) 神經細胞 (Nerve Cells and Behavior ). ( 二 ) 內分泌系統 (The Endocrine System).
發育 (The Development of Behavior ).
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07 發育 (Development)
Influences on Behavior development The concept of sensitive periods The development of bird song Developmental homeostasis
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The development of behavior
A newly hatched mallard duckling Responds to its mother’s alarm call by “freezing” Responds to its mother’s assembly call by following her
Changes that occur during behavioral development contribute to fitness Immediately (i.e. the freeze response) And in adulthood (i.e. mate preference)
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The Mallard, or Wild duck (Anas platyrhynchos), probably the best-known and most recognizable of all ducks, is a dabbling duck which breeds throughout the temperate and sub-tropical America, Europe, Asia, New Zealand (where it is currently the most common duck species), and Australia.
The male birds have bright green head, while the female is light brown. The Mallard lives in wetlands, eats water plants, and is gregarious. It is also migratory. The Mallard is the ancestor of all domestic ducks, and can interbreed with other species of genus Anas. This interbreeding is causing rarer species of ducks to become genetically diluted.
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Early behavioral development of a duck
Questions about development How does genetic makeup interact with the internal and
external environment? How do the nervous and endocrine systems influence
behavioral development? How do visual, auditory, or social stimuli affect
development of behaviors? Are early experiences important? What happens when a behavior stops? Does development always proceed predictably and reliably?
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Development of the nervous system
Behavior is primarily controlled by the nervous system and is intimately linked with its development Particularly early in life When development of the nervous system is rapid and
dramatic This is seen in the neural and behavioral
development of embryonic Atlantic salmon
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Behavioral development in the Atlantic salmon. Patterns of behavior emerge in parallel with the development of neural structures necessary for their performance.
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Development of an embryonic Atlantic salmon
The embryo’s heart and dorsal muscles move first Before the nervous system has formed
Next, the major motor systems appear in the spinal cord Motor neurons contacting anterior muscles allowing flexion The trunk’s sensory system develops and connects to the
skin The neural circuits for fin and jaw movements are complete Neural and behavioral development continues - all before
hatching Development of the nervous system underlies the
appearance of new patterns of behavior
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What happens to neural circuits when a behavior disappears?
Neural circuits can be dismantled or permanently altered
For example, changes occur in the tobacco hornworm during complete metamorphosis
Metamorphosis entails dramatic changes in morphology and behavior The nervous system must control three stages: larva
(caterpillar), pupa, and adult moth
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The larva of Tabacco hornworm (Manduca sexta)
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Metamorphosis of the tobacco hornworm
The neural circuitry controlling stage-specific patterns of behavior is assembled and dismantled during development
Caterpillars have abdominal prolegs They act in withdrawal reflexes, crawling and grasping the
substrate Proleg behaviors are not important to the pupa and
disappear during the larval–pupal transformation
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What causes the disappearance of prolegs?
Proleg movements are accomplished by retractor muscles Innervated by motor neurons with branching arbors
(dendrites) During the larval–pupal transformation
Dendrites of the motor neurons regress As these motor neurons die, their associated proleg
muscles degenerate and become nonfunctional.
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Why do neurons die?
Just before the transition to the pupal stage, high levels of ecdysteroid hormones trigger regression of the dendrites of the motor neurons that innervate the proleg muscles Motor neurons are removed from behavioral circuits
and proleg behaviors are lost in the pupa
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The peak in ecdysteroid hormones just before transformation to the pupa triggers dendritic regression.
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Development of nonneural structures
Behavioral change can be driven by non-neural morphological changes To perform a behavior, the animal has to develop the
necessary morphological structures Paddlefish feeding behavior changes
Larval paddlefish chase and eat zooplankton Adults consuming material strained from the water
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Paddlefish change feeding behaviors
Changes in behavior are coordinated with development of specific morphological structures
Changes in paddlefish feeding behavior parallel the development of gill rakers ( 鰓耙 ) Which strain food particles from the water Begin to develop when young fish are about 100 mm long
(4 inches) Are well-developed when young fish reach 300 mm long Feeding behavior takes on the fully adult pattern of
indiscriminate filter feeding
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The hormonal milieu( 背景 ) influences behavior
Developing animals are influenced by the hormonal milieu (environment) they experience early in life
Two examples describe the effects of exposure to androgens, such as testosterone, during the prenatal period House mice Black-headed gulls
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The Black-headed Gull or Pallas's Gull, Ichthyaetus ichthyaetus, is a large gull. This species breeds in colonies in marshes and islands from southern Russia to Mongolia. It is migratory, wintering in the eastern Mediterranean, Arabia and India. This gull nests on the ground, laying between two and four eggs.
House mice
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Prenatal ( 胎兒期的 ) exposure to androgens: house mice
In the uterus, each fetus has its own placenta Even before birth, their
endocrine glands produce hormones
They can permanently alter their own and their neighbor’s morphology, physiology, and behavior
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Fetal development can be modified by others
Development of mouse fetuses ( 鼠胎 ) can be modified by exposure to hormones secreted by contiguous ( 接觸的 ) littermates( 同窩出生者 )
Fetuses can take three intrauterine positions relative to siblings of the opposite sex Females nestled between two male littermates have
higher concentrations of testosterone than female fetuses not next to males
Hormones pass through the amniotic fluid of contiguous littermates
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Exposure to prenatal hormones affects adult mouse behavior
As a result of prenatal exposure to testosterone, adult females that were between two males in the uterus (1) are less attractive to males (2) are more aggressive to female intruders (3) mark a novel environment at a higher rate (4) maintain larger home ranges (5) experience their first estrus at a later age and (6) produce fewer viable litters
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Prenatal exposure to androgens influences young birds
A mother bird deposits androgens into the yolk of eggs In black-headed gulls, androgen levels increase with each
egg laid Higher androgen levels led to: earlier hatching; enhanced
growth and begging for food, and lower immune function Chicks direct energy to growth and competitiveness rather
than to immune function Adult birds show more frequent courtship and threat
displays, win more aggressive encounters, and lower survival
Greater deposition of androgens in last-laid eggs may enhance the growth and competitiveness of these chicks
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The environment affects behavior
The environmental temperature during embryonic development affects behavior i.e. leopard geckos have temperature-dependent sex
determination chromosomes do not determine sex
In leopard geckos, incubation temperature: Determines an individual’s gender Influences the adult’s aggressive and sexual behavior Affects behavior involve in mate choice
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Reproduction of leopard geckos
They are also known to have temperature-dependent sex determination (TSD).
Research shows that more females can be produced in predominantly cool temperatures (about 26-30˚ C) and very warm temperatures (about 34-35˚ C).
It was recorded that males can be produced at the intermediate temperatures (about 31-33˚ C).
Those born in the warmer temperatures expressed more aggressive behavior. These are known as "hot females" and are often determined to be infertile, that is unable to reproduce.
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Temperature affects gecko mate choice
Incubation temperature influences brain development Individuals have different perceptions of the opposite
sex A physical characteristic of the prenatal
environment influences the development of adult behavior
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Males reared at 30º C prefer females reared at 34º C
Males reared at 32.5º C prefer females reared at 30º C
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The postnatal environment also influences development and behavior
Comparing neural and behavioral development in captive animals reared in enriched or standard laboratory housing conditions
Enriched environments provide: Larger cages A more complex and variable physical environment Nesting material, foraging devices, toys, hiding places The opportunity for voluntary exercise Complex social groups
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Environmental enrichment changes the brain and behavior
In rodents, environmental enrichment caused structural changes in the brain Increased numbers of neurons, synapses, and dendritic
branches Increased brain weight and size
They also exhibit enhanced learning and memory In captive nonhuman primates, individuals in enriched
environments exhibit a more balanced repertoire of natural behaviors
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Enrichment reduces abnormal behaviors
Captive nonhuman primates exhibit fewer abnormal behaviors Self-injurious behaviors (e.g., self-biting and head-banging)
and Stereotypic behaviors (i.e. pacing and flipping, with no
apparent biological function) Abnormal behaviors develop in response to unavoidable
stress or fear And the inactivity, boredom, and frustration experienced in
environments lacking physical and social complexity
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Experience through play
Play is important in the normal development of behavior In many mammals, birds, reptiles and some
invertebrates But Play is easy to see, hard to define
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Play is easy to see, hard to define
It is difficult to define: there is no specific behavior pattern or series of activities that exclusively characterize it It borrows or exaggerates other behavior patterns
Play draws elements from other, functionally different behavior patterns juxtaposed in new sequences i.e. mixing components from hunting and sexual behavior
Movements are repeated more often than during non-play An aggressive dog bares its teeth, growls, and raises its hair But during a play fight, hair is not raised
It is spontaneous, voluntary, and exhibited by healthy individuals
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Various forms of play
Social play: play fighting, play chasing, sexual play Kittens and puppies chase, wrestle, and pounce Playful mounting by gazelles, precocious courtship in
turtles Locomotor play: exercise
Foals kick up their heels and gallop Young primates, including humans, swing, roll and slide Polar bear cubs climb ashore only to leap back into the
water Object play: manipulates objects
After an initial investigation, an object may become a toy Animals can change the type of play
And the form of play may change as the animal matures
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The long-term significance of play
Physical: training for strength, endurance, and muscular coordination Particularly for intraspecific fighting and prey capture
Social: practice of social skills (i.e. grooming and sexual behavior), establishment and maintenance of social bonds Also helps develop an animal’s ability to read and send
signals to communicate with other members of its species
Cognitive: learning specific skills or improving overall perceptual abilities
Play may fit into more than one category
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The concept of sensitive periods
Play, the physical environment, and changes in the animal’s nervous system or hormonal state can cause behavioral changes during development These factors have their effects during particular
windows of time, called sensitive periods Critical periods: windows of opportunity for learning
A phase of susceptibility to environmental stimuli Brief, well defined, during which exposure to certain
stimuli produce irreversible effects on subsequent behavior
The term “sensitive period” has replaced this term
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The sensitive period
Sensitive period: a time during development when certain experiences have a greater influence on the characteristics of an individual than at other stages
Why do sensitive periods in most animals occur early in life? Animals have the greatest opportunity to gain knowledge
from parents and close relatives For example, young birds learn to recognize conspecifics
during a brief sensitive period before leaving the nest During sensitive periods, animals learn appropriate cues,
not only of conspecifics, but also of the local environment
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Sensitive periods allow animals to learn about the environment
Salmon must learn the precise location of their natal stream because each population is finely adapted to its home water
Before their migration to the sea and during a sensitive period, Juvenile salmon learn the water’s unique chemical
composition (HSOB - home stream olfactory bouquet) at the site where they were spawned
The sensitive period for learning the HSOB occurs when smolts become ready for seaward migration and life
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Multiple sensitive periods
Individuals can experience multiple sensitive periods during their development
A young male songbird has sensitive periods during song learning And during sexual imprinting (learning the characteristics
of an appropriate mate) Humans have multiple sensitive periods during visual
development Different sensitive periods occur for different aspects of
vision (visual acuity, peripheral vision, motion detection)
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Sensitive periods in filial( 子女的 ) imprinting ( 印痕 ) Chicks, ducklings and
goslings follow their mother They develop a preference
for characteristics associated with their mother This attachment is unfailing,
and young even follow human “mothers”
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Goslings following their “mother”, Konrad Lorenz. Lorenz was the first scientist to study imprinting experimentally.
Greylag goose
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Imprinting is immediate and irreversible
Two processes are involved in development of following a mother Development of the predisposition( 傾向 ): a
young bird is predisposed to approach objects resembling conspecifics
In filial imprinting( 子女的印痕 ), the young bird learns, through exposure to its mother, her characteristics and then preferentially follows her
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Filial imprinting in precocial young
The two processes – development of the predisposition and filial imprinting – are localized in different regions of the brain
Filial imprinting is studied in species with precocial young, who can move about and feed on their own shortly after hatching Occurs in ducks, geese, swans, chickens, turkeys, and
quail The following response is nonexistent in young
songbirds, who are altricial – helpless in the nest
※ Precocial 剛孵化便能立即活動的
※ Altricial 孵出時光禿無毛 , 需要母鳥照顧一個時期的
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Imprinting in mallard ducklings
The auditory stimulus of the maternal call is important in filial imprinting Ducklings respond to the maternal call of their own
species without any previous exposure to it This response is an example of the predisposition
process
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A stuffed Peking hen emitting mallard calls was more effective in eliciting the following response in incubator-reared Peking ducklings( 北京小鴨 ) than a hen emitting either wood duck or chicken calls.
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Mallard ducklings have a sensitive period
Auditory experience before hatching is important It induces a predisposition to follow the mallard mother’s
assembly call During their sensitive period, they must hear their own
contentment calls or those of their siblings For them to prefer the call of a mallard hen
The sensitive period occurs during embryonic development Exposure after hatching does not producing the preference
for the normal call of their species Ducklings with normal embryonic auditory experience
always choose a mallard’s call over a chicken’s
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Visual stimuli affect the following response
Both auditory and visual stimuli are critical for the following response Auditory stimulation from the mother prompts
ducklings to leave the nest and follow her The hen’s appearance becomes important after leaving
the nest
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Important generalizations about early behavioral development in ducklings
Embryonic experience also influences behavior Many stimuli go into developing a single pattern of
behavior The importance of different stimuli changes as the
young animal matures Visual and auditory stimuli are important in the following
response The priorities of these cues match the timing of
development of these systems
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Sexual imprinting in birds
Sexual imprinting: early experience with parents and siblings influences sexual preferences in adulthood for many species Sexual preferences develop after filial preferences Although the sensitive periods may overlap Sexual imprinting is shown in the preferences of
sexually mature birds for individuals of the opposite Sex Unlike filial imprinting, sexual imprinting occurs in both
altricial and precocial birds
※ Precocial 孵化後,能立即活動的
※ Altricial 孵出後光禿無毛,需要母鳥照顧一個時期的
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Sexual imprinting in the altricial zebra finch
Given a choice, male zebra finch raised by Bengalese finches courted Bengalese females
Brief contact with foster parents early in life exerts a more powerful, longer-lasting influence on mate preference than long-term social contact in adulthood However, most eventually mate with a conspecific
female Sexual imprinting occurs in two stages:
The acquisition stage ( 獲取階段 ) The consolidation stage ( 鞏固階段 )
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Bengalese Finch
Zebra Finch
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The two stages of sexual imprinting
The acquisition stage A young male forms a social bond to its parents Because of this bond, the male prefers to socialize with
members of its parents’ species This preference guides his first courtship attempts
The consolidation (stabilization) stage The male courts a female for the first time During courtship, the social preference for the parental
species becomes linked to sexual behavior Once ended, no new preferences can be established
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Acquisition and consolidation are different processes
The strength of the social preference in the acquisition phase is influenced by the amount of food fed to the young male
Consolidation is most affected by the degree to which the male is aroused at the time of courtship
The functional significance of sexual imprinting Animals learn to identify and choose mates similar but
not identical to their family members
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Sexual imprinting in the precocial Japanese quail
They prefer to mate with individuals that are similar yet slightly different from members of their immediate family They judge genetic distance by plumage characteristics
Males and females prefer to spend time near first cousins Siblings are too familiar Novel unrelated animals are too different
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Japanese quail prefer to spend time near individuals that are similar to, yet slightly different from, members of their immediate family. (a) apparatus used to test preferences of adult quail.
(b) both male (shown as triangles) and female quail (shown as circles) prefer first cousins.
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Sexual imprinting in free-living birds
Great tits cross fostered to blue tits preferred their host species Sexual imprinting had occurred
Blue tits cross-fostered to great tits mated with conspecifics They had not sexually imprinted on their host species
Pied flycatchers cross-fostered to blue and great tits did not sexually imprint on either host species
Decreased sensitivity to sexual imprinting occurs in Solitary rather than social species Polygynous rather than monogamous species Cross-fostering to a socially dominant or distantly related
host species
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Sexual imprinting
← Great tits
← Blue tits
Pied flycatchers →
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Do mammals sexually imprint?
In cross fostered sheep and goats Males strongly preferred foster females, even after years
of exposure to their genetic species Females had weaker, reversible preferences for foster
males They learn characteristics of an appropriate mate from
their mother Facial features are critical in forming social and mating
preferences in mammals
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Maternal attachment
Another imprinting-like process in mammals Some ungulate species form a lasting bond between the
mother and young right after birth The mother cares exclusively for her own offspring Precocial young can wander away from their mother
soon after birth The bond must be established early
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Development of the mother’s attachment
The mother-young bond depends on mutual recognition and bonding
Right after parturition, mothers accept any young Mothers are maternally responsive but not selective Attachment requires maternal contact with offspring during
sensitive periods immediately after birth Developing maternal attachment in sheep and goats consists of
Activation of maternal responsiveness - the display of maternal behavior when in the presence of young and
Establishment of maternal selectivity - directing maternal behavior only toward young the mother has bonded with
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Sensitive periods for responsiveness and selectivity
Undisturbed female sheep and goats display maternal behavior within minutes of giving birth If the young is removed before she has had contact with it,
maternal responsiveness permanently fades within hours A few minutes or hours of contact maintains responsiveness The sensitive period lasts from birth to 12 hours postpartum
The sensitive period for development of selectivity lies within the sensitive period for maternal responsiveness (2 hours postpartum) Most mothers need only 30 minutes of contact with offspring
during the sensitive period to display selective behavior
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Which cues are important in maternal bonding?
The mother’s olfactory system is vital in both processes Particularly olfactory cues from the amniotic fluid However, the two processes differ in their ability to
compensate for loss of olfaction Loss of olfaction prevents the development of maternal
selectivity but not maternal responsiveness Without olfactory cues, mothers rely on other sensory
cues from neonates to display maternal behavior However, they do not selectively respond to their own
offspring
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Brood care in ants
Other animal groups also have sensitive periods Ants live in complex societies
Labor is divided Roles change dramatically and repeatedly over a few
weeks In the Neotropical ant, an individual’s job changes
with age Ants isolated 2 days after emergence had the most
serious abnormalities
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Ants have sensitive periods
The sensitive period: the first four days after emergence When workers are isolated immediately after
emergence, their development is simply put on hold Reintroduction into the colony mimics an emergence
It is not the physiologically defined first four days of life that is important for the development of brood care behavior But the first four days of social contact
The sensitive period must be uninterrupted to ensure normal behavioral development
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The development of bird song
There is a continuous interplay between the developing bird and its internal and external environment
The zebra finch: a social Australian species Song functions in mate attraction Only males sing Females are attracted to their song Males tolerate other birds, except in the immediate
vicinity of their nests
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The neural substrates of song.
Song nuclei: several areas of the brain are involved in song Posterior pathway: involved in song production Anterior pathway: involved in song acquisition
Other areas of the brain function in song perception (hearing) And in the storage of memories of song heard when young
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Sexual differentiation of the zebra finch brain
Zebra finches have obvious neuroanatomical sex differences Male song nuclei have more and larger neurons This is not true for all songbird species
Genes on the sex chromosomes affect the brain’s synthesis of estrogen Higher estrogen levels in male brain tissue
masculinize the song system
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Hormonal effects on singing
Hormones have both organizational and activational effects on singing behavior Estrogen early in life organizes development of a male
song system High testosterone levels in adulthood activates singing
behavior Brains are not always sensitive to the organizing effects
of estrogen The brain is sensitive to hormonal influences around the
time of hatching When estrogen affects the developing nervous system
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Hormonal activation of song is seasonal
Song occurrence is related to the breeding season Song nuclei also change in seasonally breeding birds
Increases in neuron number, density, metabolic capacity, and spontaneous neurophysiological activity
Gonadal testosterone and its metabolites act on the song nucleus (the HVC) Which then influences other song nuclei
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Role of learning in song development
White-crowned sparrows are songbirds from North America
A young male sparrow hears the songs of his father and other adult males during his first summer and autumn
He produces only subsong A highly variable, rambling series of sounds The syllables are not typical of the full song of adult males
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White-crowned sparrow songs develop
As the first breeding season approaches, “plastic song” occurs in the male His song begins to contain elements recognizable as
white-crowned sparrow syllables As the male continues to refine his song, his song crystallizes
By his first breeding season, he produces the full song of adult males
Imitations of those he heard many months before The sensitive period for song learning is between 10 and 50
days posthatching Young male reared in isolation develop abnormal song
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The role of auditory feedback in song learning
For song to develop normally, male white-crowned sparrows must Hear adult males of their species sing Hear himself sing And compare his vocal output to songs he memorized
Auditory feedback is needed For song development But maybe not for maintaining song Depending on song complexity or the ability to modify
songs in adulthood
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Sonograms of songs that were produced by white-crowned sparrows (a) reared under natural conditions, (b) reared in social isolation, and (c) deafened at an early age.
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The phases of song development
Sensory phase: songs are learned and stored Males learn only subsong, which does not involve
retrieval or rehearsal Acquisition: song is learned Storage: song is retained in memory
Sensorimotor phase: singing learned song actually begins Retrieval and production - learned song is rehearsed
and matched to the sounds they memorized months earlier
Motor stabilization - song is crystallized into final adult song, remaining unchanged for the rest of his life
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Songs can be dropped or modified
Young males may drop songs from their plastic song repertoire Ending up with 8-11 songs
Songs are not dropped at random Songs that don’t match neighbor’s are discarded
Sharing songs helps neighboring males communicate Allow them to avoid costly territorial battles
Modifying songs make them less similar to neighbor’s songs May promote individual recognition
Song learning is a balance between copying the songs of neighboring males and the need for individuality
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Sensitive periods in song learning
Sensitive periods have some degree of flexibility or variability They are influenced by environmental conditions Wide variation exists among and within songbird
species The sensitive period’s length and timing for learning varies
Lifelong learners (open-ended species) continually revise their songs throughout adulthood, i.e. canaries
Age-limited learners (closed-ended species): the period of learning occurs during the first weeks or months of life
i.e. white-crowned sparrows and zebra finches
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How do male cowbirds learn their songs?
Brown-headed cowbirds are brood parasites Females lay eggs in other species’ nests Foster parents raise the babies
Shouldn’t they sing their foster parent’s songs? But adult males sing cowbird song
When does the sensitive period for song learning occur in brood parasites? It is delayed to give them time to hear the songs of
adult male conspecifics
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Brown-headed cowbirds are brood parasites
Brown-headed Cowbird females can lay 36 eggs in a season. More than 140 different species of birds are known to have raised young cowbirds.
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Sensitive periods for song learning vary within a species Individual differences in the timing of song learning can
be understood in the context of life histories Maximizing the chances that each male develops
species-appropriate singing behavior In the marsh wren, vocal learning is influenced by
photoperiod Males that hatched late in the breeding season learned
songs the following spring Late hatched young that disperse further than early
hatched young learn songs the following spring from neighbors
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Own-species bias in song learning
Social interactions in song learning are very important Own-species bias: when given a choice, young male
birds learn their songs from conspecifics Learning the songs of their own species more rapidly
and accurately than those of a different species But, live tutors of another species can override the
bias for learning taped conspecific songs Young male sparrows learn the song of the adult that
they are allowed to interact with Even if this adult belongs to another species
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Social factors and song development
Cowbird song development is influenced by interactions with conspecifics in flocks
Cowbird song development is influenced by interactions with conspecifics in flocks Males living in mixed-sex groups learn to suppress their
song to avoid attacks from dominant males Adult males influence the potency of song produced by
young males and also the rate at which song develops.
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Female cowbirds prefer the songs of males reared in isolation to those of male reared socially.
Males without visual or direct contact with dominant males produce more potent songs than do males that have visual or direct contact. In cowbirds, young males learn to modify their songs to avoid attack by adult males.
Male cowbirds reared in isolation had more appealing songs than group-reared males
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Females help shape songs of males
Male cowbirds housed with conspecifics or other species developed different songs Song development was biased toward their female
companions’ preferences Even if they are different species
Males housed with females from their own population developed stereotyped (full) song faster than males housed with females from a different population
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Important factors in shaping bird songs
Female cowbirds influence male song development Not by song, but by moving one or both wings rapidly
away from the body Male cowbirds adjust their songs to their audience
To avoid conflict with males and stimulate available females
Social factors help shape the songs of other songbird species The “selective attrition” phase: young males drop songs
from their plastic song repertoire that don’t match their neighbor’s
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A diversity of song learning strategies
Songbirds exhibit diverse song learning strategies The sensitive period, when young males learn song, ranges
from a brief period early in life to lifelong learning Social isolation produces abnormal song in many species Diversity exists in the number of songs that birds learn
Most birds sing less than 5 songs But some birds sing > 2,000 songs
Young males copy tutor songs Some males imitate tutor songs Others modify or invent species-typical songs that bear
no resemblance to tutor song
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Stop and think
How is it best to raise young songbirds brought to wildlife rehabilitation hospitals so they can return to their natural habitats?
Song is vital to survival and breeding success In territory maintenance and mate attraction
If you were charged with developing guidelines for housing and tutoring young songbirds brought to your rehabilitation facility, what factors would you consider in making your recommendations?
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Developmental homeostasis
Individuals develop under different physical and social conditions, and still display species-typical, normal behavior
Developmental homeostasis: developmental processes can buffer themselves against potentially harmful influences to produce functional adults Despite diverse experiences, behavioral development
proceeds in a predictable and reliable manner The developmental process demonstrates stability and
resilience under constantly changing variables Recovery of profoundly isolated chimpanzees illustrates the
resilience of the developmental process
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Rehabilitation of chimpanzees after long-term isolation Male chimpanzees were separated as infants from their
mothers and conspecifics and taken to a laboratory between 1976 and 1986 to use in hepatitis and HIV research They were individually housed in cages
All experienced early maternal separation, spatial confinement, and lack of control over their daily lives They differed in when social deprivation began and the
total duration of social isolation Some had been kept in isolation for 21 years
When moved to a new facility and allowed to socialize, they became members of an all-male or mixed-sex groups
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Timing and duration of social deprivation influences chimpanzee responses
Chimps cope better with social stressors than environmental stressors Chimps perceive they have greater control over social
situations Chimpanzees that have experienced profound social
isolation, can recover and live less stressful lives with conspecifics
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Summary
Patterns of behavior appear, disappear, and alter as animals develop
Behavioral change comes about through development, hormones and experience
Play is vital to behavioral development: social play; locomotor play (exercise); and object manipulation It improves physical condition, develops social skills and
bonds, and helps develop and maintain cognitive skills Genes, hormones, the environment, experience and social
situations interact to develop sexually dimorphic behaviors
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Summary
Sensitive periods: periods of enhanced sensitivity to environmental stimuli Characterize behavioral phenomena, including
filial imprinting sexual imprinting, and maternal attachment
There are tremendous differences among species and individuals in the timing of sensitive periods
Animals encounter a wide variety of physical and social conditions, and most develop normally
Developmental homeostasis: Development proceeds in a normal fashion in the face of environmental perturbation