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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