Signals and Cues: Capturing information in an animal world

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

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

44. Navigating chemical cues

45. 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

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

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

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

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

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