4. Social Dominance Flashcards
What is the concept of dominance
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
What is Dominance?
“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)
Dominance status
– Only applicable in context of the dyad
– Describes two-way relationship within dyads
Dominance rank
– 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
Unambiguous hierarchy only exists when:
– Every dyad has a definite dominant and
subordinate member
– There are no unknown relationships
– All triadic relationships are transitive
Transitive and Intransitive Relationships
Transitive Relationship:
A
B
C
Intransitive Relationship:
ACB
BAC
CBA
Methods for Calculating Hierarchies
The I&SI Method (de Vries, 1998)
David’s Score (Gammell et al., 2003)
The Elo-rating Method (Albers & de Vries,
2001)
The Elo-rating Method (Albers & de Vries,
2001)
Estimates and continually updates
dominance ranks of individuals as
interactions occur
David’s Score (Gammell et al., 2003)
Orders individuals on overall interaction
success while taking strength of opponents
into account
The I&SI Method (de Vries, 1998)
Orders individuals in a linear/near-linear
hierarchy
Intrinsic Factors Affecting Dominance Rank
Asymmetries in Resource Holding
Power/Potential (RHP), i.e. fighting ability
Extrinsic Factors affecting Dominance
Rank
– Winner and Loser Effects
– Bystander Effects
Loser Effect
The tendency of an individual, having lost a
contest, to lose subsequent contests
Winner Effect
The tendency of an individual, having won a
contest, to win subsequent contests
Bystander Effects
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
Bystander winner effects
the bystander raises its estimation of an
individual it has just observed win
Bystander loser effects
the bystander lowers its estimation of an
individual it has just observed lose
Evolutionary Significance of Dominance
Tendency for individuals with high
dominance rank to gain greater access to
limited resources
– Food, Mates
Strongest relationships
– Ungulates, Carnivores, Rodents
In general, males exhibit greater variance
in reproductive success than females but
have greater reproductive potential.
What limits m/f reproductive success?
– reproductive success of males limited by
number of matings they can obtain
– reproductive success of females limited by
number of offspring they can produce
Why do some individuals accept the
subordinate role?
– 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
Establishment of dominance relationships in gilthead sea bream juveniles during feeding.
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
Dominance in Gilthead Sea Bream Conclusion:
– 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
Dominance in Gilthead Sea Bream Methods:
– 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
About Gilthead Sea Bream
- 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
