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
Receiver
Unintended receiver
Signaller
Information
Decision and response
Communication
Measurement
Individuals A
and B
performs X1
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
CommunicationIf H = number of bits
If N = number of messages
N = 2H or
H = log2N
Amount of information in a signal
Shannon-Weaver IndexH(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 MWHigh volatilityLow distinctiveness
High MWLow volatility
High distinctiveness
A B C
Alarm calls
Sexual attractants
Territorial marks
Communication
Modalities
2. Visual
Communication
Modalities
2. Visual - Advantages
a. Fast Transmission
b. Sender is easy to locate
c. Low energy (to send)
d. Complex, rich signals
a. Unpredictable habitat complexity
b. Sender is easy to locate
c. High risk of predation
Disadvantages
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
Time
Body weight(% of initial)
Starved crickets lose 5%per day
100
50
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
Frequency
Amplitude
e.g. - acoustic signals in shallow water
Frequency
1 m
Communication
Modalities
Acoustic - signal components need to be chosen carefully
Frequency
e.g. - birds in forests
transmissibility ofsignalNumber
of bird species
Communication
Modalities
4. Tactile
Communication
Modalities
4. Tactile - Advantages
a. Need close contact
b. Limited social use
c. Low energy cost
d. Locatible
a. Very short range - low exploitation risk
b. Fast transmission
Disadvantages
Communication
Modalities
4. Tactile - Examples
Mating - Corixidae
Grooming - chimps
Feeding - gulls
Communication-Evolution of Signals-
Communication
Signals - where do they come from?
1. Incomplete functional movements
-intention movements - thwarted attacks
CommunicationSignals - where do they come from?
2. Completely formed but redirected acts
- attacks on inanimate objects
CommunicationSignals - where do they come from?
3. Contextually irrelevant displays
- gulls - in a territorial fight - revert to preening
CommunicationSignals - where do they come from?
4. Contextually correct and complete displays
Sleeking and ruffling feathers in aggressive displays
CommunicationSignals - where do they come from?
4. Contextually correct and complete displays
Conflict Muscular tension Heat production
Autonomic cooling response
Decrease insulating effect of feathers
Ruffling to allow heat to escape
Sleeking to decrease thermal gradientBoth are important as aggressive displays
Communication
Ritualization
An evolutionary process by which behaviour patterns become modified to serve as signals
Communication
Ritualization
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 Signal complexity
Number of signals
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
normal
short
longPreferred by females-but too costly?
http://www.arkive.org/jacksons-widowbird/euplectes-jacksoni/video-00.html
Percentresponse
Selective forces in shaping signals
3. Compromise and allocation
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
Signalling effort
Survivorship Reproductivesuccess
Net reproductive success
Optimum signalling effort
Selective forces in shaping signals
Signaller ReceiverIllegitimate
signaller(Mimic)
Illegitimate receiver
(Predator)
Functional system
Exploitive system
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?
1. Male predatory - doesn’t feed female
3. Male entangles prey in silk - feeds female
2.
2. Male predatory - feeds female
4. Male wraps prey in balloon- feeds female
5. Complex balloon, small prey- no feeding
6. Complex balloon, minute prey- no feeding
7. Complex balloon, no prey
MisinformationDo animals always communicate the “truth”?
Mimicry
BatesianMüllerian
MisinformationDo animals always communicate the “truth”?
Camouflage
Misinformation
How big a lie can you tell? -generally small lies are better than big ones
X
X is the model for a mimic
Variation in X
Y
Y is the mimicking animal
If ‘Y ’ changes randomly
r1 - a small change≈ 50% chance of being
closer to X
r1
r1 - a large change<< 50% chance of being closer to X
r2
Misinformation
How big a lie can you tell? -there is an effect of receiver experience
Experience
Experience
Benefits
Plausibility
little lie
big lie