W4: Social Behavior

Question 1

Groups

Answer 1

Aggregations of individuals which
range in size from a few to thousands, and include both relatively stable as well as more ephemeral (short term) aggregations.

Question 2

Costs and Benefits of Grouping

Answer 2

Benefits: 
– Acquiring food
– Reducing predation risk
Costs:
– Increased competition
– Reproductive suppression
– Increased risk of parasite or disease
transmission

Question 3

Traits of Grouping around Resources

Answer 3

• May be multi-species and ephemeral
(They will last as long as the resources
last)
• Group members need not be related
• Group size will be limited by
• Less defensible food (widely scattered
seeds) will support larger groups than
the same amount of food put in one
defensible patch

Question 4

What limits group size around resources?

Answer 4

– The amount and defensibility of the food
(whether or not one indicidual can monopolize food sources or not)
– The presence of other known patches

Question 5

Ideal Free Distribution

Answer 5

• Food intake, and presumably fitness, is
equivalent for all individuals among all
patches
• Competition and dominance makes it less
profitable to remain in a group
• Relationship matters

Question 6

What is meant by “• Competition and dominance makes it less

profitable to remain in a group” in ideal free distributions?

Answer 6

– Dominant or despotic individuals restrict access
– The presence of dominants is one reason why
groups may not be IFD

Question 7

What is meant by “relationship matters” in the ideal free distribution?

Answer 7

– In more permanent groups, relatives can
potentially gain indirect fitness and should
remain in despotic groups while non-relatives
only face costs and gain fitness only by
reproducing

Question 8

Examples of food-related benefits

Answer 8

• Groups of insectivores and carnivores may flush more prey and have greater foraging success
• Group hunting in carnivores
• Information centers in birds

Question 9

How does grouping reduce predation risk?

Answer 9

• Dilution & selfish herd effects:
the more numbers, the more alternative prey
• Detection: more eyes and ears

Question 10

How are group size effects related to predators?

Answer 10

Isolation from all predators eliminates group size effects

Question 11

Zone of Danger

Answer 11

Area around a predator in which prey are likely to be killed.

• Varies as a function of predator’s velocity and agility
• In a colony, centrally located prey may be safer than peripheral ones

Question 12

Examples of Group defensive behavior

Answer 12

• mobbing

- alarm signaling

Question 13

Thermoregulation

Answer 13

the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. This process is one aspect of homeostasis

Question 14

Types of Group Interaction

Answer 14

• Mutualism/Cooperation
• Reciprocity
• Altruism
• Selfish Behavior
• Spiteful Bevavior

Question 15

Donor vs. Recipient’s Fitness in:

Mutualism/Cooperation

Answer 15

Donor: +
Recipient: +

Question 16

Donor vs. Recipient’s Fitness in:

Reciprocity

Answer 16

Donor: (delayed) +
Recipient: +

Question 17

Donor vs. Recipient’s Fitness in:

Altruism

Answer 17

Donor: -
Recipient: +

Question 18

Donor vs. Recipient’s Fitness in:

Selfish Behavior

Answer 18

Donor: +
Recipient: -

Question 19

Donor vs. Recipient’s Fitness in:

Spiteful Behavior

Answer 19

Donor: -
Recipient: -

Question 20

Altruism/Altruistic Behavior

Answer 20

• Behaviors that have a fitness cost to the actor but a fitness benefit to the recipient