Signals

Chapter 7--Ridley

Modified: 2005-12-09

• Definitions of Communication
  • Many definitions exist, most involve:
    • Message
    • Sender
    • Receiver
    • Most definitions also require an intentional relationship between sender and message
• Channels of Communication (not in book)
  • Auditory:
    • ADVANTAGES
      • Possibility of many signals
      • Short lasting signals
      • Works in dark and out of line of sight
      • Work at a distance
    • DISADVANTAGES
      • Localization of position
  • Visual
    • ADVANTAGES
      • Short lasting signals
      • Do not work in dark (exception: photoluminescence)
    • DISADVANTAGES
      • Limited range
      • Require close cooperation between sender and receiver
  • Chemical (most common type)
    • ADVANTAGES
      • Work in dark and out of line of sight
      • Energy, little required to produce signal
    • DISADVANTAGES
      • Long lasting signal
      • Limited number of signals
      • Slow fade out of signal
• Bird Song
  • Easily studied
  • Males sing more
    • Territorial defense
      • Parus major males may sing as many as 8 songs
    • Stimulate female reproduction
  • Alarm Calls
    • Acoustically similar
• Vervet Monkey Alarm Calls (not in book)
  • Vervet monkeys give three alarm calls:
    • Eagles
    • Leopards
    • Snakes
    • Examples
    • Monkeys ignore alarm calls given by juveniles
• Pheromones
  • Chemical signals emitted by one conspecific and detected by another
    • Bombykol

  

  • Ants
    • Antennae detect odor of pheronome
    • Food attractant pheromones (recruitment)
    • Slave raids (Dufour's gland)
    • Colony odors
    • Alarm pheromones

• Honeybee Communication
  • Honeybee worker life cycle
    • Open Cell: Eggs--3 days, Larva--5 days, Sealed Cell: Larva/Pupa--13 days, Emergence: Summer--6 weeks, Winter--6 months
    • Worker duties (typical)
      • 1-3 days: cleaning cells and incubating brood
      • 4-6 days: Feeding larva (older)
      • 7-12 days: Feeding larver (younger)
      • 13-18 days: making honey, making wax, packing pollen
      • 19-21 days: hive defense and early flights
      • 21-42 days: foraging
  • Round and Waggle Dances
    • The waggle dance (simple diagram)
      • Used mostly for food (nectar), but also for water and nest sites
      • Dance is symbolic because dance is is different plane than world
      • Karl von Frisch
        • studied bees using step and fan experiments
        • decoded the dance
        • disbelief, at first
        • 1973 Nobel Prize, eventually, shared with Konrad Lorenz and Niko Tinbergen
      • Details of dance
    • National Zoo article about bee communication
• The Evolution of Signals
  • Evolutionary Origin of signals
    • Choice of signal reflects the animal's environment
    • Ancestry: signals evolve from older, non-signalling behaviors
    • Intention Movements
      • Precede a movement: looking at watch, sitting up, chair grasp
      • Often they signal a threat
        • upright signal in gulls
        • frown in humans
        • "bowing up"
      • Evolutionary path is likely from original behavior sequence
    • Displacement Activities
      • Resolution of competing motivations into a third, unrelated, behavior
        • Birds preen instead of fleeing or attacking
        • Scratching
        • Cleaning house
        • Combing your hair (think of scene in Grease where Travolta and his rival begin combing their hair after hugging)
        • Eating
        • Shop
        • Organize
    • Autonomic Nervous System Activities
      • Involuntary signals which arise from autonomic nervous system
        • Urination and defecation
        • Shouting
        • Blushing
        • Trembling
        • Voice changes
  • Ritualization
    • Making a signal more detectable
      • Upright posture in gulls is stiff, rigid, and obvious
      • Dog signals
        • Ears, tail, and mouth used to indicate dominance, submission, aggression, and fear
        • Picture (careful, it crashes Internet Explorer)
      • Hand signals
        • Open hand up
        • Shaking hands
  • Honesty in Signals
    • Honest signals occur where signaller and signallee both benefit
      • Alarm calls
    • Honest signals are cheap in terms of energy
    • Dishonest signals occur when signaller attempts to bluff signallee
      • Threat displays
      • "I'm bigger than you." (But, I'm not really.)
    • Arms Race
      • Eventually bluff will be called
      • Richie and Fonz before fight
        • http://www.tv.com/richie-fights-back/episode/20518/summary.html
        • http://www.sitcomsonline.com/pictures3.html
    • Cost of dishonest signal may reduce effect of signal
      • "I'm rich."
• Pictures
  • Hass's pictures of faces
  • Hass's pictures of faces 2