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Behavioral Ecology. Chapter 43. Animal Behavior. Observable coordinated responses to stimuli Originates with genes that direct the formation of tissues and organs of the animal body. Genes and Behavior . Some variations in behavior have a genetic basis

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Behavioral ecology l.jpg

Behavioral Ecology

Chapter 43


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Animal Behavior

  • Observable coordinated responses to stimuli

  • Originates with genes that direct the formation of tissues and organs of the animal body


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Genes and Behavior

  • Some variations in behavior have a genetic basis

  • Arnold showed that garter snakes’ taste for slugs has genetic basis

  • Hybrid snakes showed behavior intermediate between parental types


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Nervous System

  • Detects processes and integrates information about stimuli

  • Commands muscles and glands to make suitable responses


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Hormones and Behavior

  • Hormones are gene products that influence the mechanisms required for particular forms of behavior


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Instinctive Behavior

  • Performed without having been learned

  • Usually triggered by simple sign stimuli

  • Response is a stereotyped motor program, a fixed-action pattern


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Learned Behavior

  • Responses change with experience

  • Some categories of learned behavior:

    Imprinting Spatial learning Insight learning Habituation

    Classical conditioning

    Operant conditioning


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Imprinting

  • Time-dependent learning

  • Triggered by exposure to a sign stimulus during a sensitive period

  • Young geese imprint on a moving object and treat it as “mother”


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Bird Song: Instinct + Learning

  • Bird comes prewired to listen to certain acoustical cues; instinctively pays attention to particular sounds

  • Which dialect the bird sings depends on what song it hears; it learns the details of the song from others around it


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Adaptive Behavior

  • Behavior that promotes propagation of an individual’s genes

  • Its frequency will be maintained or increase in successive generations


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Selfish and Altruistic Behavior

  • Selfish behavior promotes an individual’s genes at the expense of others

  • Altruistic behavior helps others at the expense of the altruist; may be adaptive under certain circumstances


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Starling Nest Decoration

  • Starlings line nest with wild carrot

  • Experiments have shown this behavior is adaptive

Experimental nests

Control nests


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Communication Signals

  • Intraspecific signals will evolve only if they benefit both signaler and receiver

  • Variety of signal modalities:

    Pheromones Tactile signals

    Acoustical signals

    Visual signals


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Pheromones

  • Chemical signals that diffuse through air or water

  • May bring about behavioral change in receiver or cause physiological change (priming pheromones)


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Acoustical Signals

  • Sounds used in communication

  • Used to attract mates, secure territory, warn off rivals

  • May also be used to communicate danger, keep groups together


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Visual Displays

  • Important in courtship and in aggression

  • Baring of teeth by baboon communicates threat

  • Play bow in wolves solicits play behavior

  • Flashing of fireflies attracts mates


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Signal Variation

  • Some signals never vary

  • Other signals can be varied to convey information about the signaler

  • Composite signals combine information encoded in more than one cue; more potential for variation and information


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Tactile Display

  • Signaler and receiver communicate by touch

  • Honeybee dance language


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Ritualized Displays

  • Common behavior patterns are exaggerated and simplified

  • Body parts may be enhanced or colored in way that enhances the display

  • Ritualization is often important in courtship displays


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Unintended Signal Recipients

  • Members of a different species sometimes act illegitimately as a communication signaler or receiver

  • Example: two calls of male tungara frogs – one says “dinner here” to fringe-lipped bats


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Sexual Selection

  • Reproductive success is measured in number of offspring produced

  • Reproductive success can be enhanced by increasing the number of matings or the quality of mates


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Male Reproductive Strategy

  • Males produce energetically inexpensive sperm

  • Males often provide no parental care

  • Males maximize reproductive success by mating with as many females as possible


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Female Reproductive Strategy

  • Females produce large, energetically expensive eggs

  • Females often provide parental care

  • Females increase reproductive success by increasing the quality of their mates


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Choosy Females

  • Female choice can dictate rules of male competition and shape male behavior

  • Selects for males that appeal to females

  • Male sage grouse display in leks

  • Male hangingflies offer nuptial gifts


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Male Contests

  • Females of some species cluster in groups

  • Males of such species may fight one another for access to harems

  • Selects for large males that can defeat other males in contests


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Parenting Behavior

  • Enhancing the survival of offspring can increase parents’ reproductive success

  • Parental behavior comes at a cost; drains time and effort that could be spent producing additional offspring


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Benefits of Social Living

  • Improved detection of predators; many eyes

  • Improved repulsion of predators

    • Musk oxen

    • Sawflies


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Selfish Herd

  • A group held together by self-interest

  • Other members of the group form a living shield against predators

  • Individuals may compete for the safest spots; positions in the center of the group


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Dominance Hierarchy

  • Some individuals accept subordinate status to others

  • Dominant members have higher reproductive success than subordinates

  • Subordinates may do better over long term than if they were on their own


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Costs of Social Living

  • Increased competition for food, mates, and other limiting resources

  • Increased vulnerability to disease and parasitism

  • Risk of exploitation by other group members


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Altruistic Behavior

  • Nonbreeding helpers are found in mammals, birds, and insects

  • Altruists apparently sacrifice their reproductive success to help others

  • How are genes for altruism perpetuated?


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Social Insects

  • Workers in colonies of social insects are sterile

  • These colonies are extended families

  • Workers pass on their genes indirectly by helping relatives reproduce


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Honeybees

  • Workers are sterile females

  • A single queen is the mother of all members of the colony

  • At certain times of the year, the colony produces drones--fertile males that leave the colony and mate


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Termites

  • Workers and soldiers are sterile

  • A single queen and one or more kings are the parents of the entire colony


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Naked Mole-Rats

  • Only mammals known to have a sterile worker caste

  • Single queen reproduces with one to three males

  • DNA evidence shows clan members are all closely related


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Theory of Indirect Selection

  • Proposed by William Hamilton

  • Genes associated with caring for relatives may be favored by selection

  • Altruists pass on genes indirectly, by helping relatives who have copies of those genes to survive and reproduce


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Considering Human Behavior

  • Some human behavior may be adaptive or may have been adaptive in the past

  • Testing hypotheses about human behavior can help us understand how they arose


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Moral Questions

  • A behavior that is adaptive may or may not be desirable or moral


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