Lecture 30: Mallon

Question 1

When is a signal honest?

Answer 1

If on average it conveys correct or useful information

–> doesnt have to always be truthful so one can cheat

Question 2

What is a cue?

Answer 2

Feature of the world which can be used as a guide for future action

Question 3

What is a signal?

Answer 3

Act or structure that alters the behaviour of another organism which evolved because of that effect.
It is effective because the receiver’s response has also evolved.

Question 4

What is an index?

What is handicap?

Answer 4

A signal that can’t be faked
A handicap is a signal that is costly to fake

Difficult to distinguish between the two
Generally in the common interest of sender and recipient

Question 5

What is an example of an index?

Answer 5

Stag’s bellowing
Pitch of broadcast croaks
Male hammerhead bat- size of larynx, enlarged cheeks, inflated nasal cavities, funnel shaped mouth.
Royal flycatcher

Question 6

Why is stag’s bellowing an example of an index?

Answer 6

Lower the pitch = larger the animal (lower voicebox)
Males attempt to defend a harem of females

Stags bellow to put off competitors –> walk around each other –> who is bigger (cant decide) –> fight (30% lead to permanent damage)

Question 7

How is pitch of broadcast croaks an index?

Answer 7

Lower pitch = larger individuals
Experiment - see if medium sized frogs attack silenced individuals depending on the pitch of croak.
–> not the only cue because larger individuals attacked less even if high pitched sound played e.g. strength of kick

Question 8

What correlation is there between body size and reproductive success?

Answer 8

Positive correlation

–> females prefer recordings of lower range roars

Question 9

Can stags cheat the system?

Answer 9

Longer bellow –> lower bellow
—> this is due to the fact they retract their larynx during roar
May have evolved through arms race: lower bellow leads to reproduction –> spread of trait –> dishonest response –> balanced out –> honest trait again.

Question 10

Why are costly signals reliable?

Answer 10

Relative cost for lower quality individuals is greater

This is because higher quality males can cope with handicap better.

Question 11

What are some examples of reliable costly signals?

Answer 11

Stalk eyed flies

Question 12

Why are stalk eyed flies good examples of honest signals?

Answer 12

Longer distance between eyes = better quality male
Ends up exaggerating the distance –> becomes a handicap
—> better quality can cope better

Question 13

What are the social costs of dishonesty?

Answer 13

If you pretend to be stronger / better than you are you will be punished

Question 14

How is the paper wasp (P. dominulus) a good example of social costs?

Answer 14

Increased amounts of dots on face = increased dominance
Fight for dominance ranking
If you are not as dominant as you say you will be punished.

Question 15

How is waggle dance an index?

Answer 15

Provides information to other individuals for everyone’s benefit.
There would be no point in cheating it.

Question 16

What does quorum sensing show?

Answer 16

At low cell densities of bacteria exo-product just disappears
At high cell densities exo-product aggregates to form a plaque –> increased survival
New antibiotics may prevent high cell densities of bacteria forming.

Question 17

How is drosophila a good example of a signal?

Answer 17

Females can only mate once and have to initiate copulation as males cant.
—> Therefore males only send signal after she has (no point in wasting the effort)

Question 18

How is an anglerfish a good example of using an index to their advantage?

Answer 18

Pretends to be / looks like a worm
Works on the principal of batesian mimicry - does not occur too often (more often a worm than an anglerfish)
–> ratio must be stable –> selectional pressure

Question 19

How is a drongo a good example of using an index to their advantage?

Answer 19

Shout out warning signals to meerkats

• Mostly accurate (actually warning signals)
• Sometimes use the warning signals to steal the meerkats food.