Exam 4 will cover new material through end of Animal Behavior Unit

(will complete lecture material for exam on Wednesday)

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

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.

Approaches to investigating how genes affect behavior

•Hybridization

•Artificial selection and crossing of selected strains

•Molecular analysis of genes and gene products

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

Genes and hygenic behavior in honeybees

•Uncommon instance in which behavioral trait segregates in Mendellian fashion; most behaviors are influenced by a wide array of genes

•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 component

•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

Artificial selection and cross of selected strains

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 behavior

Most elements of male courtship behavior are controlled by a single gene

sex-determining pre-mRNAs are spliced in a specific way in females and another way in males

female sxl and tra mRNAs make proteins that control splicing in the expression of genes in the female-specific hierarchy

Male sxl and tra mRNAs have stop codons that terminate translation

the default splicing of dsx mRNAs controls male anatomy

the default splicing of fru mRNAs causes formation of nervous system that expresses male courtship behavior

The fruitless gene controls male courtship in behavior in fruitflies

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).

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 efficiently

•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

Habituation

•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 adaptive…

•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 reproduction

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

Solomon & Berg 1999

Imprinting

Imprinting is learning that is limited to a specific time in an animal’s life, the critical period, and is generally irreversible

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 nest-mates and parents through eggshell; one or both parents usually present at hatching and emitting calls

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

Ducklings will imprint on the first object they see, eg black box, white sphere

Raven & Johnson 1999

Lorenz being followed by imprinted goslings

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”

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

Fox 1995

Song development in birds: a study of imprinting

•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 process

•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 template.

Sonograms of songs of white-crowned sparrows reared under three conditions

Hypothalamic-Pituitary-Gonadal Axis of Birds is Similar to that of Other Vertebrates

Environmental cues, including photoperiod, song

receptors

Hypothalamus

pituitary

bloodstream

gonads

blood stream

accessory sex organs, secondary sex characters,

including behaviors

Domestic Chicken, derived from the Jungle Fowl (Gallus gallus) [Galliformes]

Endocrine control of morphological and behavioral components of singing in male canaries

•Fernando Nottebohm ID’ed forebrain nuclei responsible for song learning in canaries

•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 vertebrates

•Hierarchical processing of motor program to vocalize is an important model for understanding how humans speak and learn to speak

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

No

. n

eu

ron

s i

n H

Vc

(x

104

)

Age (days after hatching)

High Vocal Center

(Source: Kirn and DeVoogd 1989)

•In young zebra finches, male and female song nuclei are similar; females’ nuclei undergo apoptosis, while males continue to grow

•Previously thought that brain gender 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 testosterone-like metabolite inside cells)

•experimental support; estrogen implants in young females masculinizes song control system -- induces same effects of estrogen seen in males

•Significance

•insight into brain development and neural plasticity

•potential applications of mechanisms (when worked out) include inhibition of programmed cell death

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 repertoire

•Significance; Such functional lateralization thought to occur only in humans, where it is associated with extraordinary language abilities

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 rhythms

per and tim dimerize in the cytoplasm

The dimer is translocated to the nucleus where it inhibits further transcription of the per and tim genes

Rates of transcription, translation, dimerization, may be cell-molecular components of the biological clock

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

Cognition

•Narrow sense: awareness, consciousness

•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 behavior

•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 complete

(Raven and Johnson 1999)

Starlings and certain other birds have an “internal clock” they use to compensate for the sun’s apparent movement through the sky

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 trials

dots represent pecks for food

bird is trained to seek food

in the south

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

bird with 6-hr phase advanced

rhythm now seeks

food in east

Purves et al 2001

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.

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 identifieid

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.