Signalling and Communication

Question 1

Communication

Answer 1

• where a sender uses a specially evolved signal to modify the behaviour of a receiver
• response must benefit a sender on average

Question 2

Signals

Answer 2

e. g. a stotting springbok can jump up to 6ft whilst running to confuse a predator
e. g. call of a Tungara frog attracts females
- sensory modalities - olfactory, auditory, visual, tactile, electrical

• signals work if they are honest - must be reliable and honest at least
• if they were not honest, they predators would evolve to ignore, and signallers would evolve to not send them

Question 3

Cost of signals

Answer 3

1. energy used to send a signal - could be used for other things
2. increase exposure to predators
3. with peacock feathers, costly to grow and maintain

Question 4

Deceit

Answer 4

• when an animal can exploit another to improve fitness

e. g. fork-tailed Drongo

Question 5

Unforced honesty

Answer 5

• interest of sender and receiver are congruent (i.e. mutual benefits for both parties)
• sender may be closely related to receiver, or have overlapping interests with a receiver
• if a sender benefits then the receiver will benefit and can use to own advantage

Question 6

Signalling as an arms race

Answer 6

• sender gives a signal to own advantage, at cost to a receivers fitness
• receiver gets better at discriminating signals, at cost to a senders fitness

Question 7

Index signals

Answer 7

• physically constrained, so lying is not possible
• signal production depends on a balance of costs and benefits involved for the individual signaller ( aka handicap principal)

1. difficult or costly to fake
2. signals that appear to show a disadvantage when attacked - might serve as a reliable signal of fighting ability
3. some signals involved in competitive or aggressive interactions may be produced without a direct cost (dark patches on sparrow) - black patch may lead to punishment but without

Question 8

Batesian mimicry

Answer 8

• most common as an anti predator adaption
• Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both. It is named after the English naturalist Henry Walter Bates, after his work on butterflies in the rainforests of Brazil.

– some predators will encounter palatable or harmless mimics and therefore take longer to learn to avoid the model

Question 9

Mullerian mimicry

Answer 9

• beneficial to all species involved, including the predator, as the predator learns to avoid all species faster
• Müllerian mimicry is a natural phenomenon in which two or more distasteful species, that may or may not be closely related and share one or more common predators, have come to mimic each other’s warning signals. It is named after the German naturalist Fritz Müller, who first proposed the concept in 1878.

Question 10

Developmental costs

Answer 10

• costs of learning - Finches learn to babble - neural mechanisms involved, so may be energetic
• cost of growth - antlers
• cost of allocation - caretenoids are used for feather colour, so taken away from immune system
• most animals cannot learn by imitations

Question 11

Zahavi (1975)

Answer 11

• handicap principal
• extraverted traies evolved as a signal
• used to communicate an organisms overall condition and/or genetic quality to potential mates or predators
• these signals have to be honest and costly to the signaller

1. potential mates e.g. peacock tail, elk antlers
2. parent-offspring e.g. which bird to feed
3. prey-predator -

Two types of cost

1. efficacy cost - calls have to travel long distances, but may entail expensive or exhausting consequences
2. strategic costs - costs above that if signalling

Question 12

Gould and Gould (1989)

Answer 12

• elephant seals and hareems

Question 13

Iyengar and Eisner (1999)

Answer 13

• moths

- females prefer larger males when given a choice

Question 14

Kirkpatrick and Barton (1997)

Answer 14

• male provides benefits only in genes

- alleles affecting mate choice increase or decrease in frequency depending on fitness of female offspring

Question 15

Barber et al (2001)

Answer 15

• evidence for the role of indirect effects
• female stickleback prefer red belly coloration of male sticklebacks,
• BUT also means that bright red feathers are more resistant to infection by tapeworms compared to dull feathers

Question 16

Head et al (2005)

Answer 16

• indirect effects
• female house crickets preferred to mate with attractive males
• BUT would mean they would have a shorter lifespan
• BUT would have more attractive male offspring who could attract females more easily
• although they would have a shorter life, they would attract better
• sexy son hypothesis

Question 17

Basolo (1998)

Answer 17

• females prefer males fitted with a plastic sword
• but even in fish species where no male and a plastic sword, still a female preference
• therefore preference evolved in a common ancestor

Question 18

Holland and Rice (1998)

Answer 18

• male mallard ducks drown females during conception and male bedbugs insert genitals into abdominal wall and not abdominal opening
• thereofre, females evolve resistance to male inducements, and males evolve behaviour to overcome female reluctance
• called chase away sexual selection