Evolution of Social Behavior

Question 1

Neuroethology & Evolutionary theory

Answer 1

• arise between 1960s-1975 to influence modern animal behavior studies

Question 2

Diverse criteria of sociality, Sociobiology (E.O. Wilson, 1975)

Answer 2

• # of animals that come together
• length of time group remains together
• amount of time spent in social behavior
• reciprocal communication
• division of labor (“roles”) in group
• overlap of generations & parental care
• aid-giving: “altruism”
• “eusociality”

Question 3

Eusociality

Answer 3

• reproductive division of labor (with sterility)
• overlapping generations
• cooperative care of young
• seen in insects

Question 4

Ladybugs

Answer 4

• form dense aggregations during winter –> release warming chemical allomones to ward off predators
• temporary increase in sociality to be antipredatory

also done by stiped catfish

Question 5

Allomones

Answer 5

chemical substance produced & released by individual of one species that affects behavior of another species –> benefit originator, not receiver + costly to make alone

Also produced by leaf-footed coreid bugs

Question 6

Japanese macaque grooming

Answer 6

• grooming primarily seen by females
• who is groomed can distinguish hierarchy or potential allyship –> identify “social climbers”

Question 7

Some benefits of sociality

Answer 7

• anti-predation
• increased feeding efficiency and information sharing
• facilitation of reproduction
• increased competitive ability
• division of labor
• energy efficiency
• social transmission of information

Question 8

Predation detection & numbers

Answer 8

• goshawks are less successful when they attack larger flocks of wood pigeons
• same is seen with smooth-billed ani on butterflies

Question 9

Chimpanzee predation

Answer 9

• prey on mothers w/ young
• males eat first, reward others w/ sex or some food
• males to show allyship
• columnist monkeys X fight back from slow feeding –> reduced energy

Question 10

Physiological benefits of sociality

Answer 10

• penguins & bats huddle –> minimize heat loss

Question 11

Costs of sociality

Answer 11

• increased competition for resources
• increased predation pressure
• increased transmission of disease

Question 12

“Selfish herd” hypothesis (W.D. Hamilton)

Answer 12

• origins of sociality are “selfish”
• initially, animals derive a benefit from being next to others simply because reduced likelihood that any one individual will be captured

Question 13

V.C. Wynne-Edwards

Answer 13

• animals “self-regulate” their populations through social behaviors
• for the benefit of species
• case for “group selection” - related to the view that animals sacrifice personal survival & fertility to control population growth (not a conscious choice)
• control devices: territoriality, dominance hierarchies, grouping in large flocks

Question 14

Group selection

Answer 14

S = selfish individuals
A = altruistic individuals

• differential survival of groups or populations

Question 15

Levels of Selection

Answer 15

A. individual
B. kin
C. group selection

Question 16

Richard Dawkins

Answer 16

• selection operates on genes, not individuals
• individual is embodiment of selection of thousands of selfish genes, each trying to perpetuate itself
• gene not a survival unit

Question 17

Why group selection (usually) won’t work (Williams)

Answer 17

• by generation 14, over 99% of population would be fit to “mutant” (in model of producing 3 offspring vs. 2)

Question 18

The problem of the “selfish” mutant (Larson)

Answer 18

• lemming suicide
• falsified data/observations

Question 19

Wynne-Edwards vs. Williams

Answer 19

• debate over whether traits like epideictic displays evolve for benefit of group/species
• Evolutionary biologists conclude the answer is almost always NO
• while can superficially appear as such, it’s actually the individuals that benefit

Question 20

David Lack

Answer 20

• 30+ year study of great tit (reproductive patterns, studied factors controlling numbers in natural populations)
• clutch size in great tits: selection against extremes: stabilizing selection

Question 21

Size vs. number

Answer 21

• average weight of nestlings decreases with clutch size
• more mouths to feed –> more effort
• survival of offspring is related to weight of fledging

Question 22

Experimental increase in clutch size

Answer 22

• CS 9 ideal
• Why don’t we see directional/selection impact? –> answer in adult survival (lifetime reproductive success vs. success in any one year)
• Lack’s CS hypothesis suggests birds will produce # of eggs that improve survival of adults

Question 23

Pseudomonas fluorescens

Answer 23

• cooperating groups formed due to production of adhesive (mutation, not in response to conditions) –> interests of indivduals to align w/ that of group (access to oxygen @ surface)
• as group: all survive even though most do not contribute adhesive
• if “freeloaders” reproduce too much –> mat sinks –> selection on freeloaders to reproduce less
• groups that contain enough “altruists” float survive better than groups w/ fewer altruists than that minimum number
• groups will grow + split into daughter groups –> altruistic individuals will benefit despite cost of expending resources to produce adhesive or reproducing less