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Communication Communication Definition Action on the part of one organism that alters the probability pattern of behaviour of another organism in a way that may or may not be adaptive to both Signaller Receiver Unintended receiver Signaller Information Receiver Decision and response Communication Measurement Individuals A performs X1 and B performs X2 Communication occurs if: P(X2) after X1 ≠ P(X2) without X1 Communication Measurement Units of communication - bit (binary digit) -amount of information required to control without error which of two equally probable responses will be chosen by the receiver Communication Territorial bird - raises wings - intruder leaves - lowers wings - intruder advances Each presentation of the signal = one bit of information Communication If H = number of bits If N = number of messages N = 2H or H = log2N Amount of information in a signal Shannon-Weaver Index H(X) = - ∑ pi log2 pi where pi is the probability of signal Xi Communication Kinds of signals 1. Graded -complex - signal varies with intensity Communication Kinds of signals 1. Graded -complex - signal varies with intensity Communication Kinds of signals 2. Fixed -simple - on/off signal Communication Modalities 1. Chemical Communication Modalities 1. Chemical Advantages 1. Carry a long distance 2. Low energy investment Communication Modalities 1. Chemical Disadvantages 1. Depend on wind for dissemination 2. Difficult to track and locate sender 3. Long fade time - no complex signals Communication Modalities 1. Chemical Competing selective forces Volatile - low molecular weight Species specific - high molecular weight Communication Modalities 1. Chemical Competing selective forces - trade off Low MW High volatility Low distinctiveness High MW Low volatility High distinctiveness A Alarm calls B Sexual attractants C Territorial marks Communication Modalities 2. Visual Communication Modalities 2. Visual - Advantages a. Fast Transmission Disadvantages b. Sender is easy to locate a. Unpredictable habitat complexity b. Sender is easy to locate c. Low energy (to send) c. High risk of predation d. Complex, rich signals Communication Modalities 3. Acoustic Communication Modalities 3. Acoustic - Advantages a. Long range b. Fast transmission c. Not dependent on wind d. Use at night Communication Modalities 3. Acoustic - Disadvantages a. High energy cost 100 Starved crickets lose 5% per day Body weight (% of initial) 50 Time Communication Modalities 3. Acoustic - Disadvantages b. Easy to locate sender Communication Modalities 3. Acoustic - Disadvantages c. confusion Communication Modalities Acoustic - signal components need to be chosen carefully e.g. - acoustic signals in shallow water 1m Amplitude Frequency Frequency Communication Modalities Acoustic - signal components need to be chosen carefully e.g. - birds in forests transmissibility of signal Number of bird species Frequency Communication Modalities 4. Tactile Communication Modalities 4. Tactile - Advantages a. Very short range - low exploitation risk b. Fast transmission c. Low energy cost d. Locatible Disadvantages a. Need close contact b. Limited social use Communication Modalities 4. Tactile - Examples Grooming - chimps Mating - Corixidae Feeding - gulls Communication -Evolution of Signals- Communication Signals - where do they come from? 1. Incomplete functional movements -intention movements - thwarted attacks Communication Signals - where do they come from? 2. Completely formed but redirected acts - attacks on inanimate objects Communication Signals - where do they come from? 3. Contextually irrelevant displays - gulls - in a territorial fight - revert to preening Communication Signals - where do they come from? 4. Contextually correct and complete displays Sleeking and ruffling feathers in aggressive displays Communication Signals - where do they come from? 4. Contextually correct and complete displays Conflict Muscular tension Heat production Autonomic cooling response Ruffling to allow heat to escape Both are important as aggressive displays Decrease insulating effect of feathers Sleeking to decrease thermal gradient Communication Ritualization An evolutionary process by which behaviour patterns become modified to serve as signals Communication Ritualization Communication Ritualization ? Grebe courtship Selective forces in shaping signals 1. Identification and discrimination (= reduction of ambiguity) Identify signaller as 1. Individual 2. Member of a larger group Selective forces in shaping signals 1. Identification and discrimination (= reduction of ambiguity) General trend - signals diverge or converge Factors resulting in divergence 1. Species specific sexual displays 2. Female choice in mating 3. Chance 4. Predator confusion Selective forces in shaping signals 1. Identification and discrimination (= reduction of ambiguity) General trend - signals diverge or converge Factors resulting in convergence 1. Similar ecological pressures 2. Mimicry 3. Interspecific territoriality Selective forces in shaping signals 2. Social complexity Complexity of social group Number of signals Signal complexity Selective forces in shaping signals 3. Compromise and allocation Bright colour - good for signal, not for concealment Yellow headed blackbird Selective forces in shaping signals 3. Compromise and allocation short normal Preferred by females -but too costly? long http://www.arkive.org/jacksons-widowbird/euplectes-jacksoni/video-00.html Selective forces in shaping signals 3. Compromise and allocation Percent response Selective forces in shaping signals 4. Environmental constraints Prairie chicken courtship Ruffed grouse courtship Selective forces in shaping signals 5. Sexual selection 6. Predation pressure 7. Intrasexual selection Selective forces in shaping signals Summarize the effects of signalling and survivorship Net reproductive success Reproductive success Survivorship Signalling effort Optimum signalling effort Selective forces in shaping signals Functional system Illegitimate receiver (Predator) Signaller Receiver Exploitive system Illegitimate signaller (Mimic) Evolution of Signal Systems Empididae - Balloon flies -most derived form of courtship - male presents female an empty silk balloon - balloon indicates mate quality Empididae - how did this signal come about? 2. 1. Male predatory - doesn’t feed female 2. Male predatory - feeds female 3. Male entangles prey in silk - feeds female 4. Male wraps prey in balloon- feeds female 7. Complex balloon, no prey 5. Complex balloon, small prey- no feeding 6. Complex balloon, minute prey- no feeding Misinformation Do animals always communicate the “truth”? Mimicry Batesian Müllerian Misinformation Do animals always communicate the “truth”? Camouflage Misinformation How big a lie can you tell? -generally small lies are better than big ones X is the model for a mimic Variation in X Y is the mimicking animal If ‘Y’ changes randomly r1 - a small change ≈ 50% chance of being closer to X r1 - a large change << 50% chance of being closer to X X r1 Y r2 Misinformation How big a lie can you tell? -there is an effect of receiver experience little lie big lie Plausibility Experience Benefits Experience