Intergroup Aggression

Question 1

What is the collective action problem?

Answer 1

Where there is conflict between individual interest and group interest

Question 2

What are the 2 associated scenarios with the collective action problem?

Answer 2

1) An individual may sacrifice themselves (incur more cost) for the interests of the group
2) An individual may act to save themselves (incur less cost) but reap the benefits of the group action

Question 3

What are the 3 things that groups fight over?

Answer 3

1) Resources (by both sexes) - food or territory
2) Mates (by males)
3) Intergroup dominance status - defend ability to win battles

Question 4

What is the female defense hypothesis?

Answer 4

States that males are primarily concerned with defending females during intergroup conflict

Question 5

What are the 2 predictions associated with the female defense hypothesis?

Answer 5

1) Males aggression during intergroup encounters increases when sexually receptive females are present
2) Higher-ranking males should be more active in defense (because they get more matings)

Question 6

What is the resource defense hypothesis?

Answer 6

Males benefit by defending territories important to female RS

Question 7

What is the prediction associated with the resource defense hypothesis?

Answer 7

There should be spatial patterns observed for intergroup interactions

Question 8

What is the home field advantage?

Answer 8

The probability of winning an intergroup conflict when defending access to food is highest in the center of one’s territory as opposed to the edge

Question 9

How is losing intergroup interactions measured?

Answer 9

Defined as changing course or retreating

Question 10

Which sex participates in intergroup conflict?

Answer 10

Depends on philopatry (e.g., females are involved at least sometimes in these interactions in female philopatric species, and can sometimes lead fights)

Question 11

Where is lethal raiding found?

Answer 11

Found in species with “parties” (temporary subgroups that form depending on circumstances - fission fusion systems)

Question 12

Describe the nature of intergroup aggression in troop-living species

Answer 12

There are little killings/contact aggression and very few coalitionary attacks (i.e., where multiple individuals team up against 1 or 2 individuals)

Question 13

Which species demonstrate stable troops?

Answer 13

Baboons

Question 14

What species demonstrates party living?

Answer 14

Chimpanzees

Question 15

How do we explain differences in frequency of lethal raiding between troop-living and party-living species?

Answer 15

There is increased occurence of opportunistic attack and raids (pounce-and-flees) when there is power asymmetry

Question 16

What is power asymmetry?

Answer 16

When members of one group are more numerous than members of another group (unequal group sizes)

Question 17

What does the imbalance of power hypothesis state

Answer 17

Asymmetrical distribution of power means that the dominant party can afford the cost of aggression; attackers are never seriously damaged

Question 18

What are the predictions associated with the imbalance of power hypothesis (4)?

Answer 18

1) Power asymmetry between opponents provokes attack
2) Power symmetry suppresses attack
3) Victims of aggression tend to be male
4) Intergroup dominance results in more resources

Question 19

What is the evidence for “power asymmetry between opponents provokes attack”

Answer 19

1) As party size of males increased, they are more likely to respond to calls of a single male
2) Males in small parties tend to avoid territory edges (border zones)

Question 20

What is the evidence for “power symmetry suppresses attack”

Answer 20

When there are multiple fighters on each side:
1) Prolonged interaction
2) Calls and displays but little/no contact (no deaths)
3) Repeated retreats and approaches
4) 1 or both parties withdraw in the end

Question 21

Can females become victims of aggression?

Answer 21

Sometimes, but victims are almost always male, and females are attacked less when sexually receptive

Question 22

What is the evidence for “intergroup dominance results in more resources”?

Answer 22

1) Negative correlation between IBI and territory size, where the bigger the territory = shorter IBI
2) Where raids and killings have taken place, areas were quickly taken over by dominant groups (territory expansion)

Question 23

How does intergroup conflict shape intragroup dynamics?

Answer 23

Chimpanzees are more cohesive during periods when they are more territorial (organized groups are more successful)

Question 24

Do females chimpanzees participate in intergroup encounters?

Answer 24

They do not participate directly but can:
1) vocalize prior to encounters to make the group seem larger
2) encourage attacking males through gestures

Question 25

What do bonobo intergroup interactions look like?

Answer 25

Bonobos share meat and fruit with neighbouring communities at the border