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Behavioral Ecology, Bio 407507

By Walter Hernandez,2014-08-11 08:37
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Behavioral Ecology, Bio 407507 ...

    Behavioral Ecology, Bio 407/507

    Behavioral Ecology is...

     … the study of how an animal‟s behavior relates to its ecology.

     Communication

     Foraging

     Predator avoidance

     Mating

     Parenting

     How and when do certain behaviors evolve.

    Natural Selection

     Individuals within species are variable.

     Morphology and behavior

     Trait variation must be heritable.

     Traits are passed from parents to offspring.

     Heritable traits have a strong genetic basis. More offspring are born each generation than can survive and reproduce.

     Survival and reproduction probability varies due to this trait variation.

     Survival and reproductive rate is higher for individuals with best traits.

     Key words: survival and reproduction.

     It does no good to merely survive.

    The goal of all organisms: pass as many copies of their genes into future

    generations as possible.

     "Survival of the fittest" is a little misleading. Individuals must maximize evolutionary fitness

     Fitness = measure of success of passing on genes. Fig 1.10

    Individual or Group Selection? Natural selection typically works at the level of the individual.

     Individuals don‟t do what‟s „good for the group‟.

     Ex. Individuals don‟t lower reproduction to maintain adequate food resources.

     Group rule produce 2 young.

     Cheaters produce > 2 young.

     Cheater genes spread faster in the population!

    Infanticide in Lions

     Male lions kill cubs when they take over a pride.

     1

     Induces females to go into estrous sooner.

     A male‟s tenure in a pride is brief!

     Must do what‟s in his best interest.

     Fig 1.14

    Proximate vs. Ultimate Behaviors can be explained in two general ways.

     Table 1.1

     Proximate explanations-

     How is a behavior completed?

     Physiological and mechanistic basis of behavior in the animal.

     Genes ; Protein ; Behavior & Morphology Ultimate explanations-

     Why does the behavior exist?

     Does the behavior have a selective advantage?

    Why do gulls remove shells? Proximate response to visual stimuli of open eggshell.

     Ultimate reason-

     Reduces nest predation?

     Nestlings are camouflaged.

     Egg shells attract predator attention. Experimental test.

     Place eggs in locations with/without broken eggshells nearby.

    Automeris moths

     Automeris moths display “eyespots” on hindwings when startled.

     How?

     Proximate explanation-

     Gene expression?

     Spot morphology and wing movement.

     Stimuli needed for response?

     Touch, vision, odor?

     Why?

     Ultimate explanations-

     Adaptive significance?

     Predator evasion?

     Ecological context of behavior

     When and where?

     Patterns of evolutionary transitions

     Origin and modifications?

    Testing Ultimate Explanations

     2

Examine natural variation-

     Do individuals differ in survival abilities due to variation?

     Eye spot diameter, intensity differences.

     Wing-flick rates.

     Experimental tests-

     Paint over eyespots.

     Need a control!

     Comparative tests-

     Behavior evolved multiple times in same ecological context?

     Same predator class?

    Monogamy in Prairie Voles

     Why are prairie voles monogamous when most mammals have multiple mates?

     See example pages 4-10

     Brain receptor cell differences

     V1aR expression differences

     Fig 1.3

     Why are prairie voles monogamous when most mammals have multiple mates?

     Phylogeny shows related lineages show similar behaviors.

     Fig 1.4

    Development of Behavior: Genetic Influences

    Heredity

     One assumption of natural selection:

     Behavioral traits have genetic basis.

     Trait variation is seen as differences in phenotypes Phenotypes differ due to…

     Genetic variation

     Different alleles at a gene locus.

     Individuals have different genotypes.

     and environmental influences.

    Migration in Blackcap Warblers

     Migratory path differences in different individuals.

     S. German, Scandinavia birds; Spain then W. Africa.

     C. German birds ; Great Britain.

     E. Europe birds ; Turkey, E. Africa.

     Fig 3.13

     Birds attempt to migrate in the proper direction in lab settings.

     Migratory restlessness.

     Adult and juvenile.

     3

     E. African and W. African wintering bird Hybrids-

     Intermediate migratory route

     South

    Foraging pattern in Drosophila

     Larvae are „rovers‟ or „sitters‟

     Behaviors are not environmentally induced.

     Fig. 3.19

F: Rover X Sitter cross = 100% Rovers 1

     F: 3:1 Rover:Sitter 2

     Fig 3.19

    Maternal Behavior in Mice

     fosB gene influences maternal behavior.

     Those with inactivated genes don‟t cover, nurse or retrieve pups

     Fig 3.17

    Potential for Evolution

     Artificial selection experiments demonstrate potential for behaviors to evolve.

     Mice nesting behavior.

     Fig 3.24

    Garter Snake Prey Choice

     Thamnophis elegans

     Wet, coastal populations ; eat slugs.

     Dry, inland populations ; eat fish & frogs.

     Fig 3.20

     Raise baby snakes in lab and isolate after hatching.

     Food choice experiments

     Choice between slug & fish meat

     10 trials.

     Fig 3.21

     Measure tounge flicks with slug & fish dipped cotton swabs

     10 trials.

     Fig 3.22

     Hybrid snakes show intermediate responses to slugs. Coastal populations have genetics to recognize slugs as food.

     Were these genes important in colonization of coastal areas by inland

    snakes?

     Allow utilization of novel food source?

    Development of Behavior: Environmental Influences

     4

    Early Environmental Input

     Development of behaviors in some species requires the appropriate context

    early in life.

     Marsh tits who are prevented from caching food early in life can‟t do so later

    in life.

     Appropriate neurostructure fails to develop.

     Clark‟s nutcracker caching a seed

     Fig 3.8

     Imprinting- social learning based on early experience.

     Geese imprint on individuals seen in early development in nest.

     Including humans and non-living, moving objects.

     Lifetime influence.

     They court imprinted subjects when adult.

     Fig 3.5

    Learning

     Kin recognition is another form of early learning.

     Phenotype matching

     Often based on odors

     Often certain skills are learned:

     Foraging

     Noxious prey

     Capture and handling skills

     Bee rubbing in bee-eaters

     Song in many songbirds

     Northern Mockingbird

     Song Sparrow

    Environment & Development

     Environmental variation can affect development, which in turn affects behavior.

     Ex. Typical vs. cannibalistic forms of tiger salamanders.

     Fig. 3.33

    Behavioral Flexibility

     Cannibals develop from large individuals in dense populations.

     Especially if mixed relatedness.

     Flexibility important:

     not always beneficial to be a cannibal.

    Environment & Development

     Environmental variation can affect development, which in turn affects behavior.

     5

     Ex. Sex change in some fishes.

     Protandrous species

     Male first, female second

     Protogynous species

     Female first, male second

     Change depends on the population size and sex ratio

    Behavioral Flexibility

     Thynnine wasps-

     Males learn to avoid the locations of deceptive orchids when searching for

    mates.

     Flexibility allows for increased mating success.

     Fig 3.35, 36

     Why not always have flexibility and ability to learn? Costly

     Learning ability correlated with neural tissue mass.

     Marsh wrens differ 25% in brain mass with differing song learning abilities.

     Neural tissue is especially costly to develop and maintain Human brain = 2% body mass

     Receives 15% cardiac output.

     Accounts for 20% of metabolism.

     Human behavior is particularly flexible.

     Needed in complex social systems.

     Culture

     Expect flexibility and learning to evolve only when needed.

     Generalist diets

     Seasonal changes in food availability.

     Migratory individual‟s use of different environments.

    Spatial Learning in Voles

     Male and female prairie voles make similar numbers of errors in learning to

    navigate mazes.

     Monogamous

     Males of non-monogamous species make fewer mistakes.

     Selected for traveling among multiple female territories.

     Fig 3.38

    Evolution of Communication

“The cooperative transfer of information from a signaler to a receiver”.

     Ultimate reasons for communication.

     Adaptive significance

     6

     Evolutionary history

     Proximate levels (Chapter 2).

     Genes

     Hormones

     Neurophysiology

     Environmental influences

     Individuals should signal only when it’s in their best interest.

    Communication in Spotted Hyenas Highly social, permanent clans of dozens of individuals.

     Cooperative hunting of large game.

     Communicate via erect “penis” examination.

     Females also have a phallic structure

     Pseudopenis

     Fig 9.1

     Evolutionary history of this trait?

     Anogenital sniffing is common behavior in dogs and other hyena species.

     Having a pseudopenis is unique.

     Fig 9.1

     Anatomically an enlarged clitoris.

     Due, in part, to “male” hormones produced by females when pregnant.

     Likely ancestral mutant female produced slightly enlarged clitoris.

     Gradual evolutionary change to get to today‟s structure.

     How can a pseudopenis increase a female‟s fitness?

     10-20% females die in birthing due to birth canal passing through the

    pseudopenis.

     Fig 9.3

     Selective advantage?

     Androgens given to fetuses increases their aggression.

     Establish early dominance in cohort

     Establish dominance as adult

     pseudopenis is an unselected consequence (side-effect)?

     Fig 9.4, 9.5

     Pseudopenis used for a display function?

     Used in greeting ceremonies-

     Benefits to signaler and receiver?

     Similar to how subordinate males display?

     Signal of subordinate status

     Dominant individuals determine that subordinates are not a reproductive

    threat.

     Check hormone levels

     7

     Subordinates signal agreement to cooperate in group behavior.

     In return they are not attacked by dominants.

    Using Preadapted Traits

     Whistling moth, Australia

     Males rub wing “castanets” together.

     Challenge to other males

     Mating call for females

     Fig 9.6

     Most insects can‟t hear

     Hearing has evolved in some moths for detection of bats

     Communication for territory defense and mate attraction has evolved

    secondarily in this species

     Bowerbird vocalizations

     Most species produce male aggression calls

     „Skrraa‟ call

     One clade has evolved a modification of this call as a female attraction call.

     Fig 9.12

    Sensory Exploitation

     Using sensory mechanisms for communication that previously had another

    function.

     Some water mites-

     Males mimic vibration of copepod prey to get

    female‟s attention.

     Fig 9.13

     Water mites-

     Male deposits spermatophores and signals for female to pick them up.

     Males exploit females‟ preexisting sensory sensitivities

     More efficient communication.

     Possible evolutionary patterns.

     Fig 9.14

     Elbow Orchid flowers look and smell like female thynnine wasps.

     Orchids attract males who are searching for females.

     Illegitimate signalers

     Increases pollination efficiency.

     Fig 3.35

     Swordtail and platyfish females prefer long-tailed males.

     Female preference evolved first.

     Reason for preference is unclear.

     Fig 9.20

     Female signal preference in túngara frogs.

     Males of some species have a “whine” call.

     Males of other species have “whine” & “chuck” calls.

     8

     Females of all species prefer calls with a chuck component.

     Fig 9.30

     Chucks can be costly to males.

     Not always used in „chucking‟ species

     Bats twice as likely to attack when chuck added. Males more likely to chuck in large groups.

     Less chance of being the one attacked. Bats are illegitimate receivers.

    Why Do Ravens Call at a Carcass? Attracts other ravens.

     Competition for food.

     Fig 9.23

     Attract larger predator to help open up carcass?

     No support

     Call even when carcass is easy to consume. Attract other birds as protection from predators?

     Dilution effect?

     No support

     Sometimes don‟t call if alone or in a pair

     Call to attract a gang?

     Young birds gang up on territorial owners

     Territorial owners don‟t call

     Has supporting data.

     Fig 9.24

    Why Do Baby Birds Beg Loudly? Attracts predators to the nest

     Ground-nesting young have softer, higher frequency calls than those in tree

    nests.

     Fig 9.25

     So, why call at all?

     Two hypotheses

     Sibling scramble competition-

     Try to out compete nest-mates to get more food and grow faster.

     American Robin example, pg 301

     Honest signal-

     Bird begging intensity allows parents to distribute food efficiently.

     Nestlings could increase the chance of sibling survival Not necessarily mutually exclusive.

     Likely depends on food delivery rate and nestling need.

     9

    Selection for Communication Efficiency

     Song-Habitat Match

     Dense habitats-

     Low frequencies, narrow range

     Open habitats-

     Broader range and higher frequencies

     Great Tits, Fig 2.19

    Warning Vocalizations

     Birds have other vocalizations to indicate the presence of danger.

     Mobbing calls- used to attract other birds to help attack a predator.

     Alarm call- warn of potential predator attack.

     Mobbing calls are easy for other songbirds to locate and respond to.

     Broad range of frequencies

     Fig 9.31

     Alarm calls more difficult for predator to hear and locate

     Higher and narrower frequencies

     Warning vocalizations show convergent evolution.

     Same basic call evolving independently in different species.

     Fig 9.33

    Contest Communication

     Many conflicts between animals are settled with behavioral displays

     Conflict doesn‟t always go to a physical fight.

     Even animals that have evolved weapons rarely use them.

     Why?

     Fig 9.36

     Bufo bufo male toads attempt to dislodge males from copulatory positions on females.

     Vocalizations determine persistence.

     Deep croak.

     Challenger likely leaves.

     Deep Croak = large frog

     Honest signal of abilities.

     Small frogs are better-off not wasting time/energy.

     Larger frog benefits too.

     Small males with artificially produced deep croaks face fewer challenges.

     Fig 9.34

     Honest signals are true indications of individual abilities.

     Indicate health and fighting abilities.

     Only honest signals are evolutionarily stable in contests.

     Deceiving signals eventually are ignored.

     10

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