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Behavioral Ecology. Chapter 32. Animal Behavior. Definition: Actions of an animal in response to stimuli. Nervous and Endocrine systems play important role by secreting hormones or neurotransmitters. . Genes and Behavior . Some variations in behavior have a genetic basis

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Behavioral ecology l.jpg

Behavioral Ecology

Chapter 32

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Animal Behavior

  • Definition: Actions of an animal in response to stimuli.

  • Nervous and Endocrine systems play important role by secreting hormones or neurotransmitters.

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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

    • Costal garter snake – banana slug

    • Inland garter snake – tadpoles and fish

    • Newborns – only ate species specific food

    • Hybrids –

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Hormones and Behavior

  • In voles, hormone oxytocin affects pair bonding

  • When hormone is blocked, pair-bonded females dump their partners

  • Brains of monogamous vole species have more oxytocin and ADH receptors

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Instinctive Behavior

  • Performed without learning experience

  • Usually triggered by simple sign stimuli

  • Response is a stereotyped motor program

    • FIXED

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Learned Behavior

  • Responses change with experiences

  • Imprinting

    • Time dependent form of learning

    • Triggered by exposure to a simple sign stimulus

    • Ex: Sound of cars

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Bird Song: Instinct + Learning

  • Male birds instinctively recognize a basic song

  • 10 to 50 days after hatching, a bird learns his particular regional variation from others around him

  • Birds in soundproof chambers never pick up the other songs.

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Adaptive Behavior

  • Defined as: Behavior that helps an individual propagate it’s own genes.

  • Gene frequency will be maintained or will increase in successive generations

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Selfish, Altruistic, and Social 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

  • Social behavior – interdependent interactions among individuals

    • Social sacrifice -

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Communication Signals

  • Intraspecific signals evolve only if they benefit both species involved. (ex poison ivy )

  • Types of signals

    Pheromones Tactile signals

    Visual signals Acoustical signals

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  • Chemical signals between members of same species

    • diffuse through air or water

  • Signaling pheromones

    • Induce immediate response

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Tactile Display

  • Signaler and receiver communicate by contact

  • Honeybee dance language

food close

food distant

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Visual Displays

  • Important in dominance hierarchies

  • Baring of teeth by baboon communicates threat

  • Play bow in wolves solicits play behavior

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Acoustical Signals

  • Sounds used in communication

  • Lots of examples:

    --Dog barking

    --Bird chirping



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Signal Variation

  • Some signals never vary

    • Zebra ears flat on head always = HOSTILE

  • Composite signals combine information encoded in more than one cue

    • Zebra with ears flat on head and mouth wide open = VERY HOSTILE

  • Signals vary based on context

    • Lion roar = Threat or trying to contact others

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Sexual Selection

  • Choosiness in selecting a mate

  • Success is measured by number of offspring produced

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Reproductive Strategy



Produce large, energetically expensive eggs

Often provide parental care

Reproductive success increases by increasing quality of mates – NOT number of mates

  • Produce energetically inexpensive sperm

  • Often provide no parental care

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

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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

    • Male hangingflies offer gifts

    • Male fiddler crabs wave enormous claws

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Male Contests

  • Females of some species cluster in groups

  • Males may fight one another for access to females

  • Selects for: Strength and aggressiveness.

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Parenting Behavior

  • Enhancing survival of offspring increases parents’ reproductive success

  • Parental behavior comes at a cost:

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Benefits of Social Living

  • Improved detection or repulsion of enemies

  • Cooperative hunters probably live together to enjoy other benefits (shared care for their young)

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Dominance Hierarchy

  • Some individuals accept subordinate status

  • Higher ranked members have higher reproductive success than subordinates

  • So why stay if you are ranked low?

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Costs of Social Living

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

  • Attractive to preditors

  • Increased vulnerability to disease and parasitism

  • Risk of exploitation by other group members

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Hormones and Bonding in Humans

  • Autistic children

    • Can’t form normal social relationships

    • Have lower oxytocin levels

  • Oxytocin is released in response to

    • Nursing – “cuddle hormone”

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Population Ecology

Chapter 28

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The Human Touch

  • Polynesians settled a fertile island about A.D. 350

  • By 1400, population soared, exhausting natural resources

  • By the 1700s, only a few hundred survivors and no resources remained

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Population Demographics

Population size Number of individuals that make up the gene pool.

  • Age structure Number of individuals in each age category.

  • Reproductive base Individuals that are able to reproduce.

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Population Demographics cont.

  • Population density Number of individuals in a specific area.

  • Population distribution How individuals are dispersed.

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Density and Distribution

  • Crude density information is more useful if combined with distribution data


nearly uniform


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Zero Population Growth

  • Interval in which number of births is balanced by number of deaths

  • Assume no change as a result of migration

  • Population size remains stable

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Exponential Growth

  • Population size grows by increasing increments

  • The larger the population, the more individuals reproduce

  • All populations grow like this if death rate is lower than birth rate

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Limiting Factors

  • Any essential resource that is in short supply

  • All limiting factors acting on a population dictate sustainable population size

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Carrying Capacity

  • Definition: The maximum number of individules of a species that an environment can sustain

  • Logistic growth occurs when population size is limited by carrying capacity

initial carrying capacity

new carrying capacity

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Overshooting Capacity

  • Population may temporarily increase above carrying capacity

  • Overshoot is usually followed by a crash; dramatic increase in deaths

Reindeer on St. Matthew’s Island

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Survivorship Curves

  • Type I populations:

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Survivorship Curves

  • Type II populations constant death rate

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Survivorship Curves

  • Type III populations: High death rate for young

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Human Population Growth

  • Population exceeds 6.6 billion

  • Rates of increase vary among countries

  • Average annual increase is 1.3%

    • By 2050: 8.9 billion

  • Population continues to increase exponentially

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Skyrocketing Growth

  • Humans expanded into new habitats and climates

  • Agriculture and fossil fuels increased carrying capacity

  • Hygiene and medicine neutralize density-dependent controls

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Environmental Impacts

  • United States has 4.6% of world’s population

    • Produces 21% of goods

    • Consumes 25% of nonrenewable resources

    • Generates 25% of world pollution and trash

  • India has 15% of world’s population

    • Produces 1% of goods

    • Uses 3% of nonrenewable resources

    • Generates 3% of trash and waste