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

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 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