Evolution of Communication Flashcards
(13 cards)
What are the two types of communication?
Deceptive communication
Honest communication
Give some examples of deceptive communication
Some flies and moths mimic wasp patterns to warn off predators
Cuckoo birds mimic cries of host chicks
Sexual deception:
- some orchids (e.g. fly and bee orchids) mimic male conspecific so female collects pollen from flower
- bolas spiders attract male moths by mimicking female moth pheromones
How does sexual selection play a role in communication?
Female choice selects for male traits that persuade females to mate with them which leads to co-evolutionary arms race between sexes
What are the three main ways animal signals may be honest?
1) Common interest e.g. honeybee communication and raven yelling
2) Handicap/cost e.g. begging by chicks and male displays to attract females
3) Index of quality (uncheatable signals) e.g. body weight/size or volume and depth of calls
What were some proposed hypothesis for raven yellings? Give the pros and cons of these hypothesis
1) Attract carcass opener e.g. a bear and this incidently causes more ravens to join - CONS = lone ravens finding carcass often did not yell and ravens at an opened carcass sometimes yelled
2) Selfish herding - attract more ravens in case predator attacks - CONS = lone ravens finding carcass often did not yell and yelling continued at carcasses with many ravens
3) Overwhelm defence of territory holders PROS:
- territory holding ravens didnt yell
- non-resident ravens yelled
- yelling attracted other ravens to carcass
- territory holders unable to repel many non-residents
- carcasses eaten by 1 or 2 or many ravens
Why do chicks beg?
Parents often give more food to chicks that beg more
Why feed chicks that beg more?
As amount of food received by chick increases so does the survival of the chick
Hungry chicks benefit the most from begging
Why dont chicks maximally beg no matter their need?
Begging is costly
Experiments showed artifical nests more likely to be predated when begging calls are played
Begging of tree nesters attarcts more predators than begging of ground-nesters. Predation is lower in trees than ground so can beg louder
Therefore the cost is causing this to be an honest signal
What is the optimum begging intensity?
Amount of begging that maximises the benefit to cost ratio
Less benefit for less hungry chick to beg for more food - benefit is close to the cost
How is relatedness relevant to begging intesnsity in chicks?
Cost of begging reducing causes the optimum begging intesnity to rise
In birds with higher percentage of extra-pair parentage the cost of begging is reduced due to lower relatedness of nestmates
How is male display an honest signal?
Some displays are costly to the male such as peacock feathers
If the handicap is more costly to make for a low quality male than higher quality male then the optimum size of display will correlate with male quality
Male display can be revealing signal of male quality when the display is costly
How are uncheatbale signals honest communication?
Signals are honest as they cannot be faked/cheated
In toads (and many species) large males make deeper calls than smaller males and this cannot be cheated as smaller males do not have enough size to fake the calls
Other males know that a deeper call means a larger male and so they face less attacks than higher pitched males (played sound of deeper male call for a smaller male and he faced less attacks than when higher pitch sound played)
