Lecture 14 - the evolution of communication

Question 1

2 examples of deceptive communication

Answer 1

1) cuckoo chicks decieve hosts into feeding it

2) moths can mimic hornet/wasps warning colous

Question 2

example of sexual deception in flowers

Answer 2

• fly and bee orchids - decepts the male of the species into mating with a female because their flower petals look like a female - way for the orchid to be pollinated

Question 3

example of sexual deception in fish

Answer 3

young male blue gill sunfish deceive older males by pretending to be females and sneak onto the territory to gain extra fertilisations

Question 4

example of sexual deception in a spider

Answer 4

• bolas spider attracts male moths by mimicking female moths pheremones - this works because the balance of probability that there is gonna be a female at the end of the pheromone trail is higher than the likelihood it will be a spider - the spiders cash in on this

Question 5

define sexual selection

Answer 5

Female choice selects for male traits that persuade females to mate with them…. This leads to a co-evolutionary arms race between the sexes

Question 6

what are the 3 main ways that animal signals may be honest/reliable according to maynard smith and harper

Answer 6

1) common interest
2) handicap/ cost
3) index of quality (uncheatable signals)

Question 7

example of honest communication due to common interests in honeybees?

Answer 7

waggle dance - signal to other members of the colony direction of high quality food source

Question 8

example of honest communication due to common interests with learned cues

Answer 8

• long tailed tits - cooperative breeders - their calls are individually distinctive - helpers assist relatives - calls carry a kinship signal because you learn the calls from your parents- allows discrimination from kin to kin

this is an example of ‘environmental’ cues to kinship

Question 9

example of honest communication due to common interests with genetic cues

Answer 9

’ green beard’ genes in fire ants

• all egg laying females are Bb- bb females die prematurely
• BB females are killed by Bb workers
• Bb look out for other Bb so they can lay eggs
• it it thought they recognise each other by odour cues (phenotypic effect)

Question 10

what does a ‘green beard’ gene do?

Answer 10

1) Causes a phenotypic effect
2) Permits recognition of itself in other bearers
3) Causes differential behaviour towards bearers

Question 11

who proposed the green beard gene idea?

Answer 11

Richard Dawkins - proposed in his book the selfish gene - the idea that you are nice to other individuals with the same gene

Question 12

what is an example of unrelated common interest communication?

Answer 12

raven yelling - ravens feed on carcasses - they are dependent on them in the winter to survive - they make a specific call indicating where the carcass is to other ravens

Question 13

why is raven yelling an example of honest communication?

Answer 13

because normally it would not be within their interest to share the food they have found with others but it is a technique they use when the food is on another ravens territory to overwhelm them so the territory holders couldn’t repel them - honest communication favoured by common interests

Question 14

what were the 3 initial hypotheses for why ravens yell?

Answer 14

1) Attract a “carcass opener” such as a bear (and incidentally more ravens)
2) Selfish herding: attract more ravens in case of predator attack
3) Overwhelm defence of territory holding ravens - the correct hypothesis

Question 15

another way an animals signal may be honest/reliable is through it being costly/ a handicap to them- what is an example of this?

Answer 15

chicks begging

• Parents often give more food to chicks that beg more
• Begging calls can attract predators
• the more food received by a chick the greater probability of survival
• survival curve shows that hungry chicks benefit the most from begging
• chicks dont constantly beg because the nests are more likely to be predated and it is an energetically costly process

Question 16

what experiment proved begging to have an effect on predation?

Answer 16

• Artificial nests were more likely to be predated when begging calls played
• the begging of tree nesters, attracts more predators than the begging of ground-nesters - Predation risk is lower in trees than on the ground, so tree nesters beg more loudly
• the ground nesters have a high frequency beg (high frequency sound doesn’t travel as far)

Question 17

what effect does relatedness have on begging?

Answer 17

the cost of begging is less if you are less related to siblings - positive correlation between begging loudness and extra pair percentage

Question 18

a honest costly signal can also be in terms of display explain this

Answer 18

• higher quality males have a higher probability of survival than low quality
• the signal reduces survival because is it energetically costly to carry a heavy ornament/big display
• females attracted to displays so mating increases
  display = honest signal of male quality
  = handicap that only high quality males can afford

Question 19

another way animals signals can be honest is by the the signals being uncheatable - give an example of this

Answer 19

in toads - the deeper the call the bigger size of the male and better their ability to deter rivals - honest signalling to females as they call to attract them

Question 20

some animals can cheat body size up to a point - give some examples of how they can do this

Answer 20

• Inflating abdomen
• Puffing out chest
• Making hair stand on end
• Elongating larynx to make deeper call