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Signals and Cues: Capturing information in an animal world

Signals and Cues: Capturing information in an animal world. Lesson Goals. 1) Understand the difference between signals and cues 2) What is communication? 3) How does communication evolve? 3) How does the environment influence signals?

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Signals and Cues: Capturing information in an animal world

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  1. Signals and Cues: Capturing information in an animal world

  2. Lesson Goals • 1) Understand the difference between signals and cues • 2) What is communication? • 3) How does communication evolve? • 3) How does the environment influence signals? • 4) Understand how the marine environment influences the propagation of different information modalities

  3. Information needed! • Animals perform a variety of different behaviors necessary for their survival • Foraging Locating food; handling • Mating Finding mates; advertising fitness • Defense Where and when is danger present • And all those behaviors require animals to process information about themselves and their surroundings

  4. Information Comes in Many Modalities Visual Olfaction Acoustic Electroreception IR Seismic/ Vibrational Tactile

  5. The Transfer of Information Signal Receiver Transmitter/ Sender Two Classes of Information • 1) Signal- a behavior, trait, or action intentionally generated by one individual (the transmitter) which is selected for its effects in altering the behavior of a second individual (the receiver) typically a +/+ interaction Environment Cue

  6. An Example of a Signal

  7. The Transfer of Information Signal Receiver Transmitter/ Sender Two Classes of Information • 2) Cue- an unintentional action or trait from which a receiver can gather information but it has not been selected to alter the behavior of receivers +/+ or -/+ Environment Cue

  8. An example of a cue • Blue crabs track to chemical cues given off by clams

  9. How Cues Become Signals • Initially, all information begins as cues • Cues may be more likely to be selected for if the species is already sensitive to cue/modality: sensory exploitation (a pre-adaptation)

  10. How Cues Become Signals • Some species of sword tail fish don’t possess sword tails • But if you attach a false tail to a male the females suddenly prefer him!

  11. How Cues Become Signals Sensory preferences can exist in current species that have never encountered a particular signal before. Example: Female X. maculatus fish

  12. How Cues Become Signals • If a cue provokes a response from a receiver that it beneficial to the transmitter, the cue will be modified into a true signal through the process of Ritualization • The refinement of an inadvertent cue into a true signal

  13. How Cues Become Signals • Through ritualization the cue will either be simplified (reduced # of components) • exaggerated, • repeated • Or stereotyped (reduction in variance) through the process of selection • Selection will favor signals that elicit a response the benefits the sender (on average) • Selection will favor responses that benefit receivers (on average; but see deceit)

  14. True Communication • Communication: an exchange of a signal between a sender and a receiver that benefits both parties

  15. True Communication • Senders and receivers are selected to perform in their own self interest • Signals must carry honest, interesting information

  16. But what happens when the one party doesn’t benefit? • Eavesdropping- receiver intercepts a signal or cue from sender • - (S) /+ (R) interactions (but can vary)

  17. Example of eavesdropping • Galapagos marine iguanas and mockingbirds

  18. Example of eavesdropping • Forktaileddrongos and meerkats • Drongos occasionally make false alarm calls

  19. But what happens when the one party doesn’t benefit? • Eavesdropping- receiver intercepts a signal or cue from sender • - (S) /+ (R) interactions • Deceit- sender exploits a sensory bias of or a pre-existing signal to receivers to benefit themselves • + (S)/- (R) interaction

  20. Example of Deceit • Photuris fireflies • Female Photuris fireflies flash at male fireflies (in a different genus) to suggest they are a receptive mate • And instead eat the incoming firefly!

  21. Example of Deceit • Cuttlefish have highly sophisticated chromatophores that allow them to change the color of their skin • Males and female exhibit differing patterns

  22. Deceit • Why isn't their more selection against dishonesty?

  23. Deceit • Why isn't their more selection against dishonesty? Deceptive signals are infrequent in comparison with honest signals Evolution will favor cues that clue animals about dishonest situations

  24. Maintaining Honest Signals • Why might it be hard to fake signals?

  25. Maintaining Honest Signals • Indexes- signals that cannot be faked as it is causally related to the quality being signaled

  26. Maintaining Honest Signals • Costs of producing a fake signal are high • Handicap- a signal whose reliability is ensured because it is costly to produce

  27. Maintaining Honest Signals • Both the sender and receiver have a common interest -genetic relatedness • Deception is often punished

  28. Review Receiver Benefit -/0 + + Sender Benefit -/0

  29. The Transfer of Information Signal Receiver Transmitter Environment Cue

  30. Living in a Marine World • Represented by many different habitats that will select for different cue/signal modalities

  31. Living in a Marine World • Animal behavior is often influenced by the modality of perception and its interaction with the environment

  32. Chemical Cues/Signals • Most common; most studied • Invertebrates are 95% of marine animals • Cues are released as • Pheromones (signal!) • Waste products • Leaking chemicals Kairomones

  33. Chemical Cues/Signals • Properties of these chemicals that can affect behavioral responses • Specific chemical compounds • Concentration • Spatial and temporal patterns

  34. Chemical Cues/Signals • Chemical cues are utilized in many facets of marine life • Finding Mates

  35. Chemical Cues/Signals • Chemical cues are utilized in many facets of marine life • Finding Mates • Detecting predators

  36. Chemical Cues/Signals • Chemical cues are utilized in many facets of marine life • Finding Mates • Detecting predators • Finding food

  37. Chemical Cues/Signals • Can be transported by • Diffusion

  38. Chemical Cues/Signals • Can be transported by • Diffusion • Laminar advection

  39. Chemical Cues/Signals • Can be transported by • Diffusion • Laminar advection • Turbulence

  40. Reynolds Number • Mode of transport is dictated by the Reynolds number • U – velocity • L- length of object/organism • ρ– fluid density • μ- fluid viscosity * You do not have to memorize this equation, but know that Re is a function of velocity, density, viscosity, and animal size

  41. Reynolds Numbers

  42. Reynolds Number and Chemical Cues • Moving at low reynolds numbers • Copepods

  43. Navigating chemical cues

  44. Chemical Cues/Signals • Chemical perception at higher Re is also influence by odor plume structure that is affected by multiple factors such as • Speed of release

  45. Chemical Cues/Signals • And the depth of release

  46. Chemical Cues/Signals • Water moves at different speeds at different heights due to boundary layers

  47. Chemical Cues/Signals • Different animals have developed different strategies to detect chemical sources • Blue crabs vs. whelks

  48. Visual Signals/Cues • Visual signal are likely the second most studied/common signal • Most important in vertebrate species

  49. Visual Signal/Cues • Also the most easily impaired modality • Many marine environments are very turbid

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