The evolution of communication

Question 1

Examples of deceptive communication?

Answer 1

• Hornet moth - mimics hornet to communicate that a bird shouldn’t eat it but actually it is edible to birds.
• Cuckoo chicks alter their song to sound like species it parasitises

Question 2

Examples of sexual deceptive communication

Answer 2

• Bee orchids mimic female so males will try and mate with it - gets pollinated.
• Blugill sunfish: Satellite males mimics females and sneaks copulations from dominant males territory.

Question 3

How can selection favour honest communication?

3 ways

Answer 3

1. Common interest
2. Handicap/cost
3. Index of quality (uncheatable signs)

Question 4

Honest signals: Common interest

Answer 4

• Both signaller and reciever benefit from the signal
• e.g. Honey bee communication (waggle)
• e.g. raven yelling

Question 5

Honest signal: Handicap/cost

Answer 5

• When signalling meets the costs of the individual
• e.g. Begging by chicks
• e.g. male displays to attract females

Question 6

Honest signals: Index of quality (uncheatable signals).

Answer 6

• Somehting that can’t be faked
• e.g. body size/weight
• e.g. volume and depth of calls

Question 7

Hypotheses for the adaptive significance of raven yelling

Answer 7

1. Attract a “carcass opener” e.g. bear (and incidentally more ravens)
Against → Lone ravens finding a carcass often did not yell
Against → Ravens at an opened carcass sometime did yell

2. Selfish herding: attract more ravens in case of predator attack
Against → Lone ravens finding a carcass often did not yell
Against → Yelling continued at carcasses with many ravens

3. Overwhelm defence of territory holding ravens
For → Territory holding ravens did not yell
For → Non-resident ravens yelled
For→ Yelling attracted other ravens to a carcass
For → Territory holders unable to repel many non residents
For → Carcasses eaten by 1 or 2, or by many ravens

Question 8

How would non-resident and resident ravens react to a carcas?

Answer 8

• Resident - Wouldn’t yell or attract others (keep carcas for themselves).
• Non-resident - Yell to attract other raven to help defent carcas against resident raven.

Question 9

Why is begging costly but beneficial for chicks?

Answer 9

• Chicks that beg loudly are more likely to be fed
• Loud begging puts them at risk of predation
• Hungry chicks benefit most from begging
• More food = higher survival rate
• Begging of tree living birds is louder than ground nesting (trees offer some protection)

Question 10

What is optimal begging intensity?

Answer 10

• The difference between the cost and the benefit of begging.
• Wherever gap in the greatest = optimum begging intensity for the check to exhibit
• Optimal begging intensity is lower for chicks that are partially fed or satiated.

Question 11

What is the cost of chick begging?

Answer 11

Predation

Question 12

How are begging and relatedness linked?

Answer 12

• More likely to beg if other chicks in the nest aren’t related.
• Don’t factor in the cost to them as they don’t care if the other chicks are eaten.
• Chicks that are related beg more quietly than those that aren’t related

Question 13

Signalling quality with costly display (the costs of sexual selection for bright plumage)

Answer 13

• Reduction in survival rate to a low quality male with a display (e.g. colourful feathers)
• Low quality males are better off without ornament
• Ornament is an honest indication of male quality.

Question 14

Selection will often result in deceptive communication and an evolutionary arms race between signaller and receiver, but honest signals may evolve when:

Answer 14

• There is common interest
• Signals are costly
• Signals cannot be cheated

Question 15

Honesty due to uncheatability: Toad calls

Answer 15

Deep calls = honest signal and ability to deter rivals even when actual body size is smaller (experimentally altered calls of toads)