4. Social Dominance

Question 1

What is the concept of dominance

Answer 1

Many social groups are characterised by
sustained agonistic relationships between
individuals
Where encounters are frequent enough
we gain information on the tendency of
individuals to win or lose against each of
the others in the group
* Dominance Status
* Dominance Ran

Question 2

What is Dominance?

Answer 2

“Dominance is an attribute of the pattern of
repeated, agonistic interactions between two
individuals, characterized by a consistent outcome
in favour of the same dyad member and a default
yielding response of its opponent rather than
escalation. The status of the consistent winner is
dominant and that of the loser subordinate”
(Drews, 1993)

Question 3

Dominance status

Answer 3

– Only applicable in context of the dyad
– Describes two-way relationship within dyads

Question 4

Dominance rank

Answer 4

– Only applicable in context of the group
– Group members ordered in a dominance
hierarchy based on outcome of all dyadic
interactions
– Each individual’s position in the hierarchy
represents their dominance rank relative to
all other members of the group

Question 5

Unambiguous hierarchy only exists when:

Answer 5

– Every dyad has a definite dominant and
subordinate member
– There are no unknown relationships
– All triadic relationships are transitive

Question 6

Transitive and Intransitive Relationships

Answer 6

Transitive Relationship:
A
B
C
Intransitive Relationship:
ACB
BAC
CBA

Question 7

Methods for Calculating Hierarchies

Answer 7

The I&SI Method (de Vries, 1998)
David’s Score (Gammell et al., 2003)
The Elo-rating Method (Albers & de Vries,
2001)

Question 8

The Elo-rating Method (Albers & de Vries,
2001)

Answer 8

Estimates and continually updates
dominance ranks of individuals as
interactions occur

Question 9

David’s Score (Gammell et al., 2003)

Answer 9

Orders individuals on overall interaction
success while taking strength of opponents
into account

Question 10

The I&SI Method (de Vries, 1998)

Answer 10

Orders individuals in a linear/near-linear
hierarchy

Question 11

Intrinsic Factors Affecting Dominance Rank

Answer 11

Asymmetries in Resource Holding
Power/Potential (RHP), i.e. fighting ability

Question 12

Extrinsic Factors affecting Dominance
Rank

Answer 12

– Winner and Loser Effects
– Bystander Effects

Question 13

Loser Effect

Answer 13

The tendency of an individual, having lost a
contest, to lose subsequent contests

Question 14

Winner Effect

Answer 14

The tendency of an individual, having won a
contest, to win subsequent contests

Question 15

Bystander Effects

Answer 15

Also known as Eavesdropping
Individual’s assessment of the RHP of
another individual changes based on the
outcome of a contest that it has observed

Question 16

Bystander winner effects

Answer 16

the bystander raises its estimation of an
individual it has just observed win

Question 17

Bystander loser effects

Answer 17

the bystander lowers its estimation of an
individual it has just observed lose

Question 18

Evolutionary Significance of Dominance

Answer 18

Tendency for individuals with high
dominance rank to gain greater access to
limited resources
– Food, Mates
Strongest relationships
– Ungulates, Carnivores, Rodents

Question 19

In general, males exhibit greater variance
in reproductive success than females but
have greater reproductive potential.
What limits m/f reproductive success?

Answer 19

– reproductive success of males limited by
number of matings they can obtain
– reproductive success of females limited by
number of offspring they can produce

Question 20

Why do some individuals accept the
subordinate role?

Answer 20

– Cost/benefit ratio
* Risk of injury
* Value of the resource
* Future opportunities
– Alternative mating strategies
– Cost of cheating
* Differential production and maintenance costs
* Social control of deception

Question 21

Establishment of dominance relationships in gilthead sea bream juveniles during feeding.

Answer 21

Dominant fish had significantly greater growth
rates than subordinates
* All α animals were larger than β animals at end
of experiment
– Differences were not significant

Question 22

Dominance in Gilthead Sea Bream Conclusion:

Answer 22

– Subordinate fish have lower food intake and
grow less than dominant fish
– Formation of dominance hierarchies may
affect metabolism and energy consumption
– Dominance hierarchy acting as a stressor
under these experimental conditions
* Subordinates show high levels of plasma cortisol
– Care needed when extrapolating to
commercial conditions
* Higher stocking densities than in experiment

Question 23

Dominance in Gilthead Sea Bream Methods:

Answer 23

– Three different experimental groups
* Two, five or ten fish per tank
– Fish fed three times per day until apparent satiation
* Fish began to chew but ejected whole pellets from mouth
– Fish behaviour recorded before, during and after
each feeding period with a video camera
* Social rank determined based on a number of behaviours
– Approach, attack, rebuff, chase behaviour
– Other variables measured
* Location of fish in tank during feeding
* Fish mass
* Blood and tissue samples

Question 24

About Gilthead Sea Bream

Answer 24

• Inhabits sea grass beds and sandy bottoms
  – Commonly to depths of 30m
• Euryhaline
  – Feeds in protected coastal waters
  – Open sea for breeding
• Schooling species
• One of most important fish in Mediterranean
  aquaculture