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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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animal behavior
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
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 –
hormones and behavior
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
instinctive behavior
Instinctive Behavior
  • Performed without learning experience
  • Usually triggered by simple sign stimuli
  • Response is a stereotyped motor program
    • FIXED
learned behavior
Learned Behavior
  • Responses change with experiences
  • Imprinting
    • Time dependent form of learning
    • Triggered by exposure to a simple sign stimulus
    • Ex: Sound of cars
bird song instinct learning
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.
adaptive behavior
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
selfish altruistic and social behavior
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 -
communication signals
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

  • Chemical signals between members of same species
    • diffuse through air or water
  • Signaling pheromones
    • Induce immediate response
tactile display
Tactile Display
  • Signaler and receiver communicate by contact
  • Honeybee dance language

food close

food distant

visual displays
Visual Displays
  • Important in dominance hierarchies
  • Baring of teeth by baboon communicates threat
  • Play bow in wolves solicits play behavior
acoustical signals
Acoustical Signals
  • Sounds used in communication
  • Lots of examples:

--Dog barking

--Bird chirping



signal variation
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
sexual selection
Sexual Selection
  • Choosiness in selecting a mate
  • Success is measured by number of offspring produced
reproductive strategy
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
choosy females
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
male contests
Male Contests
  • Females of some species cluster in groups
  • Males may fight one another for access to females
  • Selects for: Strength and aggressiveness.
parenting behavior
Parenting Behavior
  • Enhancing survival of offspring increases parents’ reproductive success
  • Parental behavior comes at a cost:
benefits of social living
Benefits of Social Living
  • Improved detection or repulsion of enemies
  • Cooperative hunters probably live together to enjoy other benefits (shared care for their young)
dominance hierarchy
Dominance Hierarchy
  • Some individuals accept subordinate status
  • Higher ranked members have higher reproductive success than subordinates
  • So why stay if you are ranked low?
costs of social living
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
hormones and bonding in humans
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”
the human touch
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
population demographics
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.
population demographics cont
Population Demographics cont.
  • Population density Number of individuals in a specific area.
  • Population distribution How individuals are dispersed.
density and distribution
Density and Distribution
  • Crude density information is more useful if combined with distribution data


nearly uniform


zero population growth
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
exponential growth
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
limiting factors
Limiting Factors
  • Any essential resource that is in short supply
  • All limiting factors acting on a population dictate sustainable population size
carrying capacity
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

overshooting capacity
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

survivorship curves
Survivorship Curves
  • Type I populations:
survivorship curves36
Survivorship Curves
  • Type II populations constant death rate
survivorship curves37
Survivorship Curves
  • Type III populations: High death rate for young
human population growth
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
skyrocketing growth
Skyrocketing Growth
  • Humans expanded into new habitats and climates
  • Agriculture and fossil fuels increased carrying capacity
  • Hygiene and medicine neutralize density-dependent controls
environmental impacts
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