Behavioural polymorphisms

Question 1

Animals in the same situations, don’t all respond the same way - why not?

Answer 1

1) Hormones, parasites, neurophysiology, diurnal cycles all affect behaviour – see specialist lectures.
2) Animals play different strategies.
3) Animals have different personalities.

Question 2

Can individuals in the same species play different strategies?

Answer 2

Yes and this is explored in the game theory “Hawk - Dove game”

Question 3

What is the “Hawk-Dove game”?

Answer 3

The “hawk” and “dove” are strategies played by players of the same species, NOT two different species.

Question 4

What does the Hawk do in the “Hawk-Dove game?” in regards to resources

Answer 4

HAWK: very aggressive, always fights for some resource, taken by the winner.

Question 5

In the “Hawk-Dove game”, what occurs when hawk vs hawk

Answer 5

Fights are costly. Model assumes all hawks are equally strong, so 50% chance of winning a fight.

Question 6

What does the Dove do in the “Hawk-Dove game?” in regards to resources

Answer 6

never fights for a resource. Initially displays aggression but if the opponent tries to fight, it withdraws before it gets injured. Cost is waste of time.

Question 7

What happens when Dove vs Dove in “Hawk-Dove game”

Answer 7

Dove meeting dove wins 50% of contests, but takes time.

Question 8

What happens when Hawk vs Dove in “Hawk-Dove game”

Answer 8

Dove meeting hawk, recognised as hawk quickly so little time cost, no injury.

Question 9

How do we know whether a strategy will persist?

Answer 9

By looking at it’s Evolutionary Stable Strategies

it depends on the costs and benefits of each strategy!

Question 10

What are Evolutionary Stable Strategies?

Answer 10

strategies which cannot be invaded by another strategy.

Question 11

If we have a pure population of doves, is this an evolutionary stable strategy?

Answer 11

If invaded by a hawk, the hawk wins all encounters, gets all the resources and never has to fight so would outcompete doves. So pure dove not an ESS.

Question 12

If we have a pure population of hawks, is this an evolutionary stable strategy?

Answer 12

If invaded by a dove – doves don’t pay any injury costs, but never win. So fights with hawks are neutral, and doves can persist in hawk populations as long as the resource isn’t vital. So pure hawk not an ESS either.

Question 13

Are there any values which give a stable mixed population?

Answer 13

If assume winner pays no cost and loser all the costs
you can plot this value for each frequency of hawks and doves to see if there’s any population mix which would be stable.
Where the lines cross is a stable mixture of hawks and doves.

Question 14

At the ESS point, what would happen if you added individuals of either strategy

Answer 14

lowers fitness of that strategy
More Hawks would have lower fitness than that of dove.
More Doves (fewer hawks) would have lower fitness than Hawks. 
So returns to the ESS frequency.

Question 15

What is the impact of adding a hawk?

Answer 15

As both lines have negative slopes, the addition of any Hawk lowers everyone’s fitness!

Question 16

What does the game theory explain?

Answer 16

This game explains why most animal contests involve only ritual fighting behaviours rather than outright battles.

Question 17

Describe how speckled Wood butterflies play Hawk or Dove

Answer 17

• territory ownership of a patch of light on the forest floor
• Whoever gets there first is the owner. Owners play Hawk and defend the territory
• If another male arrives in an occupied light spot, he plays Dove and retreats immediately.
• If two arrive together, they both think they own it and fight by spiralling round each other until one concedes – i.e. they both play Hawk.
  Bourgeois strategy!!

Question 18

What is the bourgeois strategy?

Answer 18

Playing Hawk when owning a territory, but Dove when invading someone else’s territory

Question 19

Give an example of animals playing bourgeois strategy?

Answer 19

Speckled Wood Butterflies

Question 20

Give an example of animals playing “anti-bourgeois” strategy

Answer 20

Mexican spiders

Question 21

How do Mexican Spiders play “anti-bourgeois strategy”

Answer 21

• territories in gaps between stones in walls and rubble.
• territory holder plays Dove, and runs away if attacked.
• attacker plays Hawk and invariably wins.
• get a domino effect of one spider displacing another all across the wall.

Question 22

Where do mexican spiders hold territory?

Answer 22

in gaps between stones in walls and rubble.

Question 23

With Mexican spiders, why does the territory holder give in so easily?

Answer 23

If there are lots of territories, but fighting is expensive, then letting an intruder have the territory and avoiding the fight is probably adaptive.

Question 24

What is anti-bourgeois strategy?

Answer 24

an individual plays Dove when the individual is an owner of the resource, whereas it plays Hawk when it is not an owner

Question 25

What is war of attrition?

Answer 25

When 2 animals meet in a contest for a resource, the amount of energy they are willing to invest to win that resource are predetermined. If instead of two choices (attack or run away) the competition is how long to hold out

Question 26

Give an example of war of attrition

Answer 26

male dung flies aggregate at dung pats to await females who lay eggs there. - The longer a male waits, the fewer new females he will encounter and the more fights he will have with other males - But if he goes away too soon he misses out on new females and pays a cost of flight to the next pat. - If lots of females at a pat, stay longer.

Question 27

What occurs the longer a male dung fly waits and the shorter he stays

Answer 27

the fewer new females he will encounter and the more fights he will have with other males if he goes away too soon he misses out on new females and pays a cost of flight to the next pat.

Question 28

Real animals play multiple strategies in different circumstances, true or false

Answer 28

True

Question 29

Why do horned beetles have different mating strategies?

Answer 29

Because there are two forms of male: Horned and Unhorned

Question 30

What are horned male beetles?

Answer 30

Horned males got good nutrition as grubs, grow large and develop horns.

Question 31

What are unhorned male beetles?

Answer 31

Unhorned males got poor nutrition as grubs, and didn’t grow big enough to grow horns.

Question 32

How do horned/unhorned beetles mate differently?

Answer 32

- Horned males stand at the entrance to the burrow and drive off intruders. - Unhorned males cannot attack them, so build a second tunnel which enters the side of the main tunnel, bypassing the male guarding the entrance. The unhorned male mates with the female behind the horned male’s back.

Question 33

How do side blotched lizards mate differently?

Answer 33

3 male morphs – orange, yellow and blue, which differ in behaviour as well as throat colour. Orange males are very aggressive and mate with lots of females by taking over the territories of other males =usurpers. Yellow males don't defend territories, but mimic females and sneak matings behind the backs of territorial males = sneakers. Blue males mate guard females so spot sneakers, but lose fights with usurpers = mate guarders So, like rock-paper-scissors; orange defeats blue, blue defeats yellow, and yellow defeats orange.

Question 34

What are the usurpers in side blotched lizards?

Answer 34

Orange males are very aggressive and mate with lots of females by taking over the territories of other males

Question 35

What are the mate guarders in side blotched lizards?

Answer 35

Blue males mate guard females so spot sneakers, but lose fights with usurpers

Question 36

What are the sneakers in side blotched lizards?

Answer 36

Yellow males don't defend territories, but mimic females and sneak matings behind the backs of territorial males

Question 37

Give an example of an evolutionarily stable situation in which no single colour morph can dominate the population.

Answer 37

All three throat colours and their associated behaviours are being maintained through the social interactions and their rock-paper-scissors polymorphism.

Question 38

Real animals play multiple strategies in different circumstances - what animals do males do this in again?

Answer 38

horned beetles, side blotched lizards

Question 39

How do guppy females have different breeding strategies?

Answer 39

Two mate choice strategies, depending on life stage and experience: If young, copy the mate choice of older females; If old, stick to your own choice.

Question 40

Real animals play multiple strategies in different circumstances - what animals do females do this in again?

Answer 40

Female – guppies; damsel flies; cuckoos

Question 41

White Throated Sparrows exist in two forms, what are they?

Answer 41

Tan and White striped

Question 42

How do White Throated Sparrows behave quite differently (Tan and White striped)

Answer 42

Tan ones are more monogamous, and care for the young better. | White striped ones sing more and are more aggressive

Question 43

With white throated sparrows, both forms that exist are quite different. Why doesn’t one strategy win?

Answer 43

Pairs mate by negative assortative mating – i.e. prefer to mate with the opposite form. Mixed pairs do best: one partner gives good parental care, the other defends the territory well. Maintains both morphs in the population. Also maintained by heterozygote advantage – the heterozygotes are healthier.

Question 44

How is feeding behaviour maintained as two strategies

Answer 44

Large Cactus Finch – one of Darwin’s finches on the Galapagos Territories of A and B males randomly distributed if unmated but alternate if mated. Living next to someone eating differently is best for your food availability. Two feeding strategies maintained because more efficient to differ from neighbour.

Question 45

How do the large cactus finches differ?

Answer 45

Males dimorphic in song type: songs A and B

Question 46

Males with song A vs Song B (large cactus finches)

Answer 46

All eat prickly pear cactus but use different bits. Males with song A have shorter bills A males (shorter beaks) tear apart the cactus base and eat the flesh and insect larvae in it. than song B males. B males (long beaks) punch holes in the cactus fruit and eat the fleshy pulp.