7. Living in Groups

Question 1

What are some of the costs of aggregating/grouping?

Answer 1

Competition for food, space, mates
Disease/Parasitism
Predator Attraction

Question 2

What are the benefits of aggregating/grouping?

Answer 2

Reduced predation risk
Improved foraging success
Defence of resources
Improved prey capture

Question 3

Aside from many eyes, dilution effect, and the selfish heard, what other behaviour can help predation when in a group?

Answer 3

Communal defence - eg Musk ox - create a circle around young, all facing out

Question 4

How does living in groups assist the location of food?

Answer 4

Social information generated by other group members. Possibly increased accuracy for when to leave a patch

Question 5

Since there are costs and benefits to group living, what must occur?

Answer 5

A trade off

Question 6

What is the Allee effect?

Answer 6

A phenomenon characterized by a correlation in individual fitness and population size

Question 7

Why are optimal group sizes often unstable?

Answer 7

Free group joining means individuals end up with the same level of fitness as they would if solitary

Question 8

Why are group sizes often not the optimal size?

Answer 8

Because the optimal sizes are unstable - individuals are free to join until the benefit to the newcomer outweighs the cost of being solitary

Question 9

What is a ‘skew’ within a group living community?

Answer 9

When the costs and benefits are unequally shared between the group
e.g. Dominance, Age, Personality, Relatedness

Question 10

What are the three simple behavioural zones?

Answer 10

Repulsion - move away
Orientation - align
Attraction - move towards

Question 11

What are the three types of group decision making?

Answer 11

Democracy
Quorum
Despotism

Question 12

What is democracy in animal groups?

Answer 12

When the majority of the group agrees - calling or head movements - rare in nature, difficult to measure?

Question 13

What is a quorum in animal groups?

Answer 13

Consensus decision - there is a threshold number of individuals needed for a decision to be made.

Question 14

What is despotism in animal groups?

Answer 14

When one or a few individuals influence the whole group’s decision - potentially the highest cost to all other individuals

buut may be beneficial when many can benefit from the knowledge of a few - eg waggle dance/matriarchs