Transcript Document

Exam 4 will cover new material through end of
Animal Behavior Unit
(will complete lecture material for exam on
Adaptive function of stereotypical,
“innate” behavior
FAP’s, triggered by simple cues do not require
extensive time otherwise required for neural
processing or integrating wide variety of inputs
Simple cue and relatively simple, stereotypical
behavior patterns are effective evolutionary
solutions to many situations in the lives of
animals, including humans.
Ultimate cause may be that for certain behaviors,
automatic and experience-independent modes of
expression may have maximized fitness to the
point that genes for variant behavior were lost.
Smiling appears spontaneously in human
infants at about four weeks. The innate nature
of this motor program is illustrated by the smile
of this eleven week old blind girl, whose eyes
are fixated on source of mother’s voice, a
complex behavior that is also innate. Smiling
helps cement a strong emotional attachment
between parent and child
Approaches to investigating how genes
affect behavior
•Artificial selection and crossing of
selected strains
•Molecular analysis of genes and gene
Hybridization experiment with two species
lovebirds demonstrates 1) phenotypic
differences in behavior are based on different
genotypes, and 2) the behavior can be
modified by experience
Artificial selection and cross of
selected strains
Genes and hygenic behavior in
•Uncommon instance in which behavioral
trait segregates in Mendellian fashion; most
behaviors are influenced by a wide array of
•Some honeybee strains express a hygenic
behavior; they remove the carcasses of
dead larvae from their nests
•Adaptive function of behavior;confers
resistance to bacterium lethal to larvae
•Two apparent components to this behavior
•uncapping larval cell (u)
•removing carcass (r)
•Cross-breeding experiments with hygenic
and non-hygenic strains reveal
•simple Mendellian segregation of the
genes coding for each behavioral
•all F1 progeny are non-hygenic;
indicates each behavioral component
is controlled by a recessive allele
•back-crossing F1 with hygenic strain
produces 3:1 phenotype ratio expected for a
two-gene trait
Molecular genetics research reveals specific genes that influence behavior
•In Drosophila, male courtship
behavior is stereotypic,
species-specific, and requires
no learning
•Sexual differentiation is
controlled by a hierarchy of
genes, and in that hierarchy,
fru controls the branch that
leads to male courthship
Most elements of male courtship behavior are controlled by a
single gene
The fruitless gene controls male courtship in behavior in fruitflies
sex-determining pre-mRNAs are spliced in a specific
way in females and another way in males
female sxl
and tra
that control
splicing in
of genes in
sex-lethal (sxl) is at the top of a gene hierarchy; it is expressed in
fly embryos with two x chromosomes (flies therefore destined to
be females).
Male sxl and
tra mRNAs
have stop
codons that
the default
splicing of
dsx mRNAs
the default
splicing of
fru mRNAs
formation of
system that
Learning: modification of
behavior due to experience
Learning in the context of
genetic and environmental
components of behavior
•Many behaviors have a strong
environmental component, and some
behaviors may seem to be entirely due to
learning, but at some level, all behaviors
have a genetic component
Learning vs. maturation in
developmentally fixed behaviors
•Most developmentally fixed behaviors
improve with performance as the animal
learns to execute the behavior more
•Modification of a developmentally fixed
behavior may be due to maturation
(ongoing developmental changes in
neuromuscular systems) in addition to or in
the absence of learning
Japanese macaque that has learned to wash
sand off of food before eating
Solomon & Berg 1999
•Habituation is a simple
form of learning in which
responsiveness to a
stimulus is lost
•animal learns to ignore a
repeated, irrelevant
stimulus, which is
•fitness is probably
increased through
habituation, by allowing
animal’s nervous system to
focus on important stimuli
that signal food, mates, or
danger, instead of wasting
time or energy on barrage
of stimuli that are irrelevant
to its survival and
After repeated safe encounters with vans transporting humans on
photo safari, many animals, including giraffes, zebras, lions, and
elephants, in the Serengeti learn to ignore them. Elephants
typically ignore the vans unless the driver provokes them by
moving too close. In that event the elephant may challenge and
even charge the van
Imprinting is learning that is limited to a
specific time in an animal’s life, the
critical period, and is generally
Imprinting is a process by which social
attachments are made early in life that
will influence behavior later in life
•Filial imprinting; social
attachments form between parents
and offspring
•Sexual imprinting; attachment
forms by which an individual learns
to direct it sexual behavior at
members of its own species
Imprinted goslings following Mom
Imprinting in birds: mechanism and adaptive function
•In many bird species, young develop a strong behavioral bond with mother
•Bond forms through imprinting, during a critical period -- usually within a few hours of hatching
•Bond forms through vocal communication; older embryos in eggs can exchange calls with nestmates and parents through eggshell; one or both parents usually present at hatching and emitting
Raven & Johnson 1999
Lorenz investigated the
phenomenon of imprinting
•Newly hatched bird imprints on the
first moving object it sees (imprinting
stimulus) and then will direct their
social behavior toward that object
•Lorenz split a clutch of graylag goose
eggs; left half with mother to incubate
and raise; they showed normal
behavior, followed her, grew up to
interact and mate with conspecifics
•Half the clutch placed incubator,
offered himself as a model for
imprinting; goslings followed him as if
he were their parent; failed to
recognize mother or other conspecifics;
as adults, tended to develop social
relationships with humans, not geese;
some initiated courtship with humans
Lorenz being followed
by imprinted goslings
Ducklings will imprint
on the first object they
see, eg black box,
white sphere
Process of imprinting is genetically determined; but bird learns to respond to a
particular animal or object
The ability or tendency to respond to first object seen after hatching is “innate”
Fox 1995
Imprinting, critical periods, now
known to occur at various times in
the life of animals, not just in very
early stages
Imprinting was initially understood as a
learning phenomenon of very young
animals (e.g., Lorenz’ geese critical period
was first two days of life)
Current understanding is that similar
learning processes occur in older animals,
and involves a variety of functions
Aspects of imprinting in young falcons
Song development in birds: a study of
Sonograms of songs of white-crowned
sparrows reared under three conditions
•Early experiments showed song
development in male white-crowned sparrows
is an imprinting phenomenon
•Two learning processes in the sparrow’s
song development
•bird must acquire a song type by
hearing an adult
•bird must learn to match this song
by listening to itself
•Later research showed variability in the
•Strong stimulus (exposure to live male
of another species) can overcome
developmentally fixed tendency to
acquire only a conspecific song
•Same strong stimulus resulted in longer
critical period (>50 days)
Males that heard tapes of conspecific songs
before day 50 (a) learned to sing normally,
months later. Males raised in soundproof
chambers (b) learned only to sing primitive
template of song. Males deafened after hearing
tapes of conspecific song, but before beginning to
practice, did not even learn the primitive
Hypothalamic-Pituitary-Gonadal Axis of Birds is Similar to that of Other
Environmental cues, including
photoperiod, song
blood stream
accessory sex organs,
secondary sex characters,
including behaviors
Domestic Chicken,
derived from the Jungle
Fowl (Gallus gallus)
Endocrine control of morphological
and behavioral components of
singing in male canaries
•Fernando Nottebohm ID’ed forebrain
nuclei responsible for song learning in
•High variation in size of nuclei among
males based on season and number of
vocalizations in repertoire; nuclei largest
during breeding season, in males with
most songs
•Reduction in nucleus size may be
mechanism for “erasing” unneeded songs
and regeneration, for learning of new
songs to take place
•One of the first demonstrations of growth
and development of neurons in adult
•Hierarchical processing of motor
program to vocalize is an important model
for understanding how humans speak
and learn to speak
•In young zebra finches, male and female song nuclei
are similar; females’ nuclei undergo apoptosis, while
males continue to grow
(Source: Kirn and DeVoogd 1989)
•Previously thought that brainHigh
differences arise because in females, tissue
doesn’t grow, but in males, homologous tissue
does grow
•cell death in brain sexual differentiation now
known or suspected in many mammalian
systems -- first elucidated in songbirds
•Mechanism in Zebra Finches
•estrogen secreted by male gonadal cells
prevents neuronal death and promotes
development of connections between some
nuclei (estrogen is converted to a testosteronelike metabolite inside cells)
•experimental support; estrogen implants in
young females masculinizes song control
system -- induces same effects of estrogen
seen in males
•insight into brain development and neural
•potential applications of mechanisms (when
worked out) include inhibition of programmed
cell death
Age (days after hatching)
Changes in the song system of young zebra
finches. The number of nerve cells in the female’s
HVc, a component of the song system, declines
rapidly as the males increases
Hormones and Sexual Dimorphism in
Behavior and Neural Circuitry
Song Control Centers and Functional Lateralization
•Nottebohm (1980)
discovers functional
lateralization of avian song;
left hemisphere dominance
•Experimental ablation of
left hemisphere song
centers; new centers
develop in right hemisphere,
function in song control; bird
develops distinct song
•Significance; Such
functional lateralization
thought to occur only in
humans, where it is
associated with
extraordinary language
HVc affects song discrimintation by females. The HVc region of the female
canary’s song system helps her discriminate between the song of male canaries and
that of other species. After destruction of the female’s HVc, she will perform
copulatory displays to tapes of white-crowned sparrows. (After Alcock 1998,
Brenowitz 1991)
Biological Rhythms
Life, lineages, evolved in 24-hour cycles of light and dark
Across kingdoms, lineages have endogenous circadian rhythms of activity -- eating,
sleeping, motor patterns (e.g. treadmill), metabolic function…
“Biological clocks”, the proximate mechanisms that drive circadian rhythms, are
fundamentally important organizers of animal behavior
The period (length of time of period) of circadian rhythm is entrained (set) by an
environmental cue; light-dark cycle; organisms deprived of the environmental cue will
continue rhythmic behavior in a free-running manner with periods that are about, but
not exactly 24 hours (“circadian” = “about a day”)
Period = one cycle length Phase= point on the cycle
Entrainment= setting, resetting of clock, via environmental cue;
drives phase advances or phase delays as well as periodicity
Marks indicate when mouse is running on activity wheel
Phylogenetic Perspective on Clocks
Circadian rhythms occur throughout kingdom Animalia; Also occur
in protistans, plants, fungi
Within animalia, among lineages, there are diversity in clocks, ie,
evolution of diversity in “location, tissue, and presumably cell
molecular mechanisms
In mammals, “master circadian clock” is located in the brain, in
two nuclei dorsal to the optic chiasm; the suprachiamatic nuclei
Genetic underpinnings of circadian rhythms. Many alleles of the
period gene of Drosophila fruit flies exist. On the left is shown the
strand of DNA that constitutes the period gene. Researchers know
precisely where different mutations have occurred in this stretch of DNA.
Each mutant allele has a characteristic effect on the activity patterns of
fruit flies, shown on the right (dark bars represent time when the flies are
active). The normal pattern of nonmutant (wild-type) flies appears at the
bottom of the diagram [Baylies et al, in Alcock 1998]
Manipulation experiment
demonstrates role of period
gene in Drosophila Wildtype
DNA from fruit flies can be
take up in plasmids, some of
which will then carry the per+
allele. The plasmids can then
be collected and microinjected
into the embryos of fruit flies
with the pero “restoring”
normal activity
Transcription and translation
of per and tim show circadian
per and tim
dimerize in the
Rates of transcription, translation, dimerization,
may be cell-molecular components of the
biological clock
The dimer is translocated to the
nucleus where it inhibits further
transcription of the per and tim
Circannual Rhythms
Moving Somewhere: Travelling requires tracking stimuli in
the environment
•Taxis: Movement towards or away from a stimulus; specific orientation.
e.g. positive phototaxis of moths to outdoor light
•Kinesis: Random movement in response to stimulus
•Migration; regular movement, often circannual and two-way, over
relatively long distances; presumably requires cognitive mapping
•Piloting: ability to move from one familiar cue to another –
considered especially important in short-distance movements
•Orientation: ability to follow a bearing (compass sense)
•Navigation: ability to set or adjust bearing and then follow it
(compass sense and map sense); requires determination of present
location and compass direction
Cues used by Birds and Animals for Orientation and Navigation
Celestial Cues
•Sun is used commonly for diurnal migrants and stars are used commonly for
nocturnal migrants
•Indigo Buntings and other species are known to use the North Star for orienting;
compensation mechanism (clock) not needed because its apparent relative position
remains unchanged
•Birds that use sun and other stars to orient presumably have internal clocks that
allow them to compensate for apparent movement of sun or star due to rotation of
the earth.
Magnetic field
•Many migrating birds and other animals have the ability to detect the earth’s
magnetic field and to orient themselves with respect to it
•Generally, birds that
•Animals known or suspected to use Earth’s magnetic field to navigate include
honeybees, some fishes and amphibians and sea turtles
Animal Cognition
•Narrow sense: awareness,
•Broad sense: ability of an
animal’s nervous system to
perceive, store, process and
use information gathered by
sensory receptors
Cognitive Ethology
•The study of animal
cognition; focuses on links
between behavioral output
and the internal data
processing by the nervous
system that gives rise to the
•One area of interest in
cognitive ethology is internal
representation of spatial
relationships in an animal’s
physical surroundings;
cognitive maps
Migration Feat: Monarch
butterflies of eastern North
America in a remote fir forest in
Mexico; the migration is over
3000 kilometers and takes from
two to five generations to
(Raven and Johnson 1999)
Purves et al 2001
pecks for
bird is
trained to
seek food
in the
bird with
6-hr phase
now seeks
food in
A pigeon placed in a circular cage from which can see
the sky (not the horizon) can be trained to seek food in
one direction, even when its cage is rotated between
Pigeon is placed on altered light-dark cycle
and its circadian rhythm is phase-advanced by
6 hrs. Bird is then returned to the training cage
under natural sky
Starlings and certain other birds have an “internal clock” they use to compensate for
the sun’s apparent movement through the sky
Magnetite, a
magnetized iron ore,
has been found in the
brains of some birds,
but the sensory
receptors birds use to
detect magnetic fields
have yet to be
Orientation of homing pigeons is influenced by changes in magnetic field. Dots show
angles at which birds flew off. Direction of home is straight up. Birds tested for two magnetic
directions, neither of which affect birds on sunny days, but both do on overcast days,
suggesting a back-up system.
Starling Migration Displacement experiments indicate that
inexperienced starlings migrate by orientation (and is largely an “innate”
behavior) while older birds that have migrated previously use true
navigation (and modify their migration behavior through experience.