sociality and social behaviour part 2 n.
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Sociality and Social Behaviour (Part 2). Reciprocity - incur a cost now in anticipation of receiving a benefit later. Altruism by non-relatives. Modelling - use Game Theory - John Nash. Prisoner ’ s Dilemma. Altruism by non-relatives. 2 prisoners - caught and jailed for a petty crime.

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altruism by non relatives1

Prisoner’s Dilemma

Altruism by non-relatives

2 prisoners - caught and jailed for a petty crime

- suspected of having committed a more serious crime

altruism by non relatives2

Prisoner’s Dilemma

Altruism by non-relatives

Each prisoner (player) has a choice

cooperate - deny all knowledge of the serious crime

defect - accuse the other of the more serious crime

Reward for defecting - forgiven minor crime

altruism by non relatives3

Prisoner’s Dilemma

Altruism by non-relatives

Each strategy has a payoff

Payoff depends on behaviour of the opponent

1. Both cooperate - both get a reward - R

2. Both defect - both get punished - P

3. One cooperates & one defects

- defector set free - T (temptation payoff)

- cooperator jailed - S (sucker’s payoff)

altruism by non relatives4

Prisoner’s Dilemma

Altruism by non-relatives

This relationship of payoffs must hold

T > R > P > S

Temptation > Reward > Punishment > Sucker’s

altruism by non relatives5

Maximum sentence - 12 years (10 for major, 2 for minor)

What are the years saved by each strategy?

Altruism by non-relatives

Player B

Plays first

Cooperate

Defect

Player A

S = 0

R = 10

Cooperate

T = 12

P = 2

Defect

altruism by non relatives6

Prisoner’s Dilemma

How should they behave?

Altruism by non-relatives

-should defect - always saves something

Player A

  • if B cooperates - T > R

-if B defects - P > S

If both defect do worse than if they cooperate

R > P

Player B

altruism by non relatives7

Prisoner’s Dilemma

How should they behave?

Altruism by non-relatives

After a number of simulations with more than

one move,

Best strategy is a tit-for-tat

-cooperate on first move and then do what opponent did on previous move

altruism by non relatives8

Prisoner’s Dilemma

Benefits of tit-for-tat

Altruism by non-relatives

Initially cooperative

Quick to retaliate

Quick to forgive

altruism

Does this work in nature?

Altruism

Kin Selection

Reciprocity

altruism1

Kin Selection

- in mate acquisition

Altruism

Wild turkeys

- male progeny of a single brood

- group for life

-dominance hierarchy - only dominant male mates

altruism2

Kin Selection

- in mate acquisition

Altruism

Reproductive success of non-mating males

-realized through RS of brother

How?

If brother mates with four females

-non-maters RS = 4 x relatedness x .5 (to account for female’s contribution)

= 4 x 0.5 x 0.5 = 1.0

altruism3

Reciprocity

- in mate acquisition

Altruism

Long tailed manakins

altruism4

Reciprocity

- in mate acquisition

Altruism

Long tailed manakins - only dominant male mates

Courtship dance

Subordinate

Dominant

altruism5

Reciprocity

- in mate acquisition

Altruism

Does subordinate male assume role of dominant?

predicted

Copulations per hour:

New alpha male

observed

Copulations per hour: previous alpha male

altruism6

Reciprocity

- in mate acquisition

Altruism

Why have 2 males?

- females are attracted to 2-male courtship groups

altruism7

Reciprocity

- in predator detection

Altruism

Meerkats - sentinels

altruism8

Reciprocity

- in predator detection

Altruism

Meerkats - sentinels

-forage in groups - not related

-every so often - one animal stands

to look for predators

-sentinel warns of approaching predator

altruism9

Reciprocity

- in predator detection

Altruism

Meerkats - sentinels

This behaviour is adaptive if:

Chance of being preyed on while acting as a sentinel

Survivorship while others are sentinels

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altruism10

Reciprocity

- in predator detection

Altruism

But is this really reciprocity?

Alternative hypothesis (selfish):

“Sentinels” are really just animals who have finished feeding and are looking for predators to protect themselves.

altruism11

But is this really reciprocity?

Some predictions from reciprocity hypothesis:

Altruism

Prediction Observation

Regular rotation of sentinel duty

Sentinel duty appears to be haphazard

Sentinel duty has risk of succumbing to predator

Sentinels are usually closer to an escape burrow

Less time is spent in predator detection in groups

No difference in sentinel time when solitary