the concept and definition of dominance - drews 1993
DESCRIPTION
Review of the concept and definition of dominance in animal behaviour.TRANSCRIPT
Behaviour 125 (3-4) 1993, © E. J. Brill, Leiden
THE CONCEPT AND DEFINITION OF DOMINANCE IN ANIMAL BEHAVIOUR
by
CARLOS DREWS1)
(Department of Zoology, Cambridge University, Downing Street, Cambridge CB2 3EJ, U.K.)
(With 1 Figure) (Ace. 7-VII-1993)
Abstract
The concept of dominance has contributed greatly to our understanding of social structurc in animals. Over the past three decades, however, a variety of concepts and definitions of dominance have been introduced, leading to an ongoing debate about thc usefulness and mcaning of the concept. Criticisms aimed at one definition of dominance do not necessarilly apply to other definitions. Existing definitions can be structural or functional, refer to roles or to agonistic behaviour, regard dominance as a property of individuals or as an attribute of dyadic encounters, concentrate on aggression or on the lack of it, and be based either on theoretical constructs or on observable behaviour. Thirteen definitions of dominance are reviewed, and their usefulness assessed with respect to their descriptive value. The predictive and explanatory values of definitions are specific to the questions asked in each particular study and are not considered as criteria to judge the usefulness of the dominance concept. By virtue of its high descriptive value, the original definition of dominance by SCHJELDERUPp-EBBE (1922, Z.Psychol. 88: 226-252) emergcd as the basis to formulate a structural definition with wide applicability and which reflects the essencc of the concept: Dominance is an attribute of the pattern of rcpcated, 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. Dominance status refers to dyads while dominance rank, high or low, refers to the position in a hierarchy and, thus, depends on group composition. Dominance is a relative measure and not an absolute property of individuals. The discussion includes reference to the heritability of dominancc, application of dominance to groups rather than individuals, and the role of individual recognition and memory during agonistic encounters.
Introduction
Dominance is a keyword in most studies of social behaviour in gregarious
animals and has contributed greatly to our understanding of social struc
ture, Tables listing dominance studies in a diversity of animal taxa are
1) I thank S.K. ELTRI~<GHAM, G.W. NORTON, and P.C. LEE for valuable discussion.
284 CARLOS DREWS
provided by DEWSBURY (1982) and GAUTHREAUX (1978). Despite the fact that dominance is such an important and widely used concept, there is
still no agreement regarding its meaning. SCH]ELDERUPP-EBBE (1922)
introduced the concept of the peck-order, later to be called dominance,
into the behavioural sciences. He vividly described his observations on
the peck-order of domestic fowl, the dynamics of the hierarchy, and the
determinants of rank. \VILSON (1975) summarized different types of domi
nance hierarchies found in animals. HArm (1986) provided an ample
discussion of the different categories found among dominance relation
ships and rigorously defined the terms commonly used in studies of
dominance. Other conceptual discussions about dominance can be found
in VAN KREVELD (1970), FEDIGAN (1982) and DUNBAR (1988).
A lively debate has underlined the application of dominance in behav
ioural studies over the past three decades (e.g. BERNSTEIN, 1981). GARTLAN
(1968) criticized the different interpretations of dominance because these
often led to ambiguity. He further criticized the fact that the term
dominance is often used without a definition or else is arbitrarily
redefined to fit the findings. ROWELL (1974) pointed out that the defini
tion of dominance is elusive. Investigators are far from a consensus on
how to define and measure dominance (BERNSTEIN, 1981), leading to
disparate opinions regarding its function and evolution. BERNSTEIN (1981)
concentrated on primates but his review of the problems associated with
the concept of dominance has general application. His article is accom
panied by comments from various investigators and thus provides an
overview of the dominance debate and lack of concensus at that time.
One of the central problems of the dominance debate has been that
critics have not always explicitly specified which definitions they advocate
and which they criticize. This has kept the debate going since the criti
cisms may have been justified with respect to a particular definition but
not to others. In this paper, an overview of the diversi ty of definitions of
dominance found in the animal behaviour literature is presented and the
usefulness of each definition assessed with respect to furthering our
understanding of social structure and behaviour. Elimination of some
definitions and finding the common denominator of others lead to a
synthesis illustrating the essence of dominance in behavioural studies.
This synthesis is condensed in the definition of dominance proposed in
the concluding section.
285 THE CONCEPT AND DEFINITION OF DOMINANCE
Categories of d.ornfnance definitions
The terms winner, loser, submissive, subordination and aggression are
part of the specialized vocabulary surrounding the dominance concept.
These terms are defined and used here as follows:
Winner: the contestant that expresses consummatory behaviour according to its initial goal (BAENNINGER, 1981; HAND, 1986). Winner/loser refers to the outcome of one single contest.
Submissive: submissiveness is an active response to an aggressive action by another individual (HANBY, 1976) in which yielding or surrendering are displays given by the loser (HAND,
1986). Submissive behaviour refers to single contests.
Subordination: to lose consistently certain conflict encounters (HAND, 1986). Subordination refers to a pattern based on several contests.
Aggression: actual attacks, threats of attack or encroachments; signals which suggest that attack may occur can be called aggressive (HAND, 1986).
Dominance definitions can be separated into those based on empirical
observations and definitions based on theoretical constructs (GAGE, 1981,
HINDE & DATTA, 1981). These have been referred to as "data-language"
and "theory-language" definitions respectively by HINDE & DATTA
(1981). GAGE (1981) distinguishes two approaches to the study of domi
nance: in the first, the investigator formulates in theory-language the
conditions which must be met by a useful application of the term domi
nance, then derives a testable hypothesis and lets the results of empirical
inquiry support the definition of dominance or else lead to its rejection. In the second approach, the investigator assumes the existence of domi
nance, asserts an operational definition, and proceeds to demonstrate the
utility of the term and definition. This latter approach is similar to the
data-language definitions mentioned by HINDE & DATTA (1981), in which
a particular behavioural interaction is given the name "dominance inter
action". More broadly, dominance is used to describe a particular kind or
set of observable interactions. The dominance definitions based on
empirical observations can in turn be subdivided into structural and
functional ones (BERNSTEIN, 1981). Structural dominance definitions
describe the pattern of an observable type or set of interactions without
referring to their function, whereas functional definitions describe domi
nance from the point of view of its apparent function.
The distinction between definitions based on empirical observations
and theoretical postulates, as well as between structural and functional
definitions is used in this discussion to broadly characterize the definitions
286 CARLOS DREWS
of dominance prescnted below. A further distinction between definitions
is whether they describe agonistic or non-agonistic dominance relation
ships (BERNSTEIN, 1981). First, the definitions of dominance based on
empirical observations are presented. These are ordered from broad
definitions to more specific ones and, as such, they are not mutually
exclusive. Then, a definition based on theoretical constructs is given.
Some definitions are included which are not explicitly referred to in the
literature, but which help in the process of categorization.
Coxrrrrron definitions of d omdnanoe
Definitions based on empirical observations.
1. "Privileged role": animals in a role which subjectively represents a
privileged position with respect to others are dominant. This definition is
illustrated by WILSON'S (1975) description of the dominance hierarchy of
food transfer from forager bees (subordinates) to nurses (dominant).
There is no overt aggression in the relationship and the subordinate bees
acquire dominant status as they grow older. This is a non-agonistic
dominance definition.
The remaining definitions include agonistic behaviour as part of the
dominance concept. First, definitions (2.-4.) are listed which consider
dominance to be an attribute of the individual. In subsequent definitions
(5.-13.) dominance is considered a relative measure, an attribute of
dyadic encounters or relationships and not a property of individuals.
2. "Reproductive status": reproductive dominance in social insects refers
to differences in reproductive status such that the reproductive individual
is the dominant and the non-reproductive ones are subordinates (WILSON,
1975). This structural definition could be regarded as a case of the
"privileged role" definition. The usc of overt aggression by the reproduc
tivcs, howcvcr,justifies a separate mcnt ion of this definition. Wh~ll two or
more paper wasp (Polistes sp.) females start a nest together, one becomes
the egg layer while the others become workers. The queen establishes her
dominant position and controls the other wasps by direct aggression
(\VEST, 1967; EBERHARD, 1969). Here, dominance refers to the reproduc
tive condition achieved and not to the pattern of aggressive interactions.
THE CONCEPT AND DEFINITION OF DOMINANCE 287
If, however, the investigator bases dominance status on the pattern of
aggression, then reproductive dominance is a functional definition
derived from the "dominance is aggressiveness" definition (see below).
3. "Dominance is aggressiveness": a dominance hierarchy is the set of
sustained aggressive-submissive relations among a group of animals
which coexist within one territory (WILSON, 1975). WILSON (1975) is
concerned with " ... dominance behaviour mediated by aggression and
inferentially based upon natural selection at the level of the individual. .. ".
The occurrence of aggressive contests over resources among any social
group of animals is indicative of dominance relationships. The expression
of the dominance system IS based on individual variation III
aggreSSIveness.
4. "Dominance IS a trait that conveys rank": a dominant individual
routinely wins encounters with significantly greater than chance proba
bility against a variety of conspecific opponents. This occurs because that
individual has more of a trait called dominance (or aggreSSIveness or
assertiveness) than do the losers (BAENNINGER, 1981).
5. "Winner is dominant, loser is subordinate": dominance status IS a
synonym for winner and loser used to describe the outcome of any single
dyadic encounter, regardless of whether or not the contest is escalated.
6. "Successful combatant": dominance ranks are established on the basis
of dyadic contests resembling a competition. Generally each dyad meets
on one or few occasions in which the decisive contest takes place. CLUT
TON-BROCK et at. (1979) established the dominance rankings of male red
deer on the basis of fighting success in the rutting season. Similarly, the
ranks of elephant seals are determined through the outcome of escalated
fights in the breeding season (LEBOEUF, 1974). The observed pattern of
interactions resembles HAND'S (1986) aggressive dominance definition, in
which the winner uses or seems willing to use the most aggression.
Dominance scores based on overall fighting success belong to this defini
tion (e.g. BOYD & SILK, 1983, ENS et al., 1990). Another example are
lekking species, in which the contest is sometimes decided on the basis of
acoustic or visual displays and may include escalated fights. This defini
288 CARLOS DREWS
tion neither implies that escalation is avoided nor that individuals recog
nize each other and incorporate past agonistic experiences into contest
decisions.
7. "Dominance IS lack of aggressiveness": dominance refers to the
"peaceful" nature of encounters between animals, in which escalated
fights do not take place and conflicts are resolved using non-agonistic
assessment or submissive behaviour. VESSEY (1981) advocates a use of the
term dominance that conveys its likely function, namely control of
resources and minimum energy expenditure through the use of displays to
control the behaviour of the receiver. Learning from past encounters and
individual recognition are not necessary conditions under this definition.
Typically, an individual recognizes a feature in the opponent which
indicates superiority (e.g. size, weaponry, quality of display) and submits
without a fight. High predictability of outcomes seems necessary under
this definition of dominance. Dominance status is assigned after a single
contest.
8. "Consistent winner of agonistic contests": when A consistently wins
agonistic encounters against B then A is dominant and B subordinate.
This definition is characterized by the asymmetry in the outcome of a
series of contests of any type and implies that A and B meet repeatedly. It
neither implies that high levels of aggression are avoided nor that individ
ual recognition and memory of other contests play a role in contest
decisions.
9. "Consistent winner in a given context": dominance is a descriptive
term for individuals that consistently win dyadic encounters in a given
context (HAND, 1986). A dominance relationship is described for each
competitive context. Dyadic relationships can be pure or mixed, since
they may exhibit different kinds of relationship for different conflict
contexts (HAND, 1986). This definition emphasizes the role of context in
determining the outcome of interactions (e.g. LEE, 1983).
10. "Priority of access to resources": dominance is by definition priority
of access to resources (VAN KREVELD, 1970; MORSE, 1974; SYME, 1974;
WILSON, 1975; GAUTHREAUX, 1978; WOLFE, 1984; WAGNER &
289 THE CONCEPT AND DEFINITION OF DOMINANCE
GAUTHREAUX, 1990). Por-r- & DEVORE (1979) define dominant/ subordi
nate as the winner/loser in contests over resources. The winner is the
contestant which displaces the other or appropriates the opponent's
resource (e.g. CLUTTON-BROCK et al., 1979). Avoidance of escalation dur
ing contests is not a requisite for dominance. It refers to obtaining what
one wants by winning a fight or without having to fight for it (RALLS,
1976). The functional, central statement of dominance is that particular
individuals in social groups have regular priority of access to resources in
competitive situations (CLUTTON-BROCK & HARVEY, 1976). Dominance
describes an asymmetry in the outcome of such contests. High ranking
individuals can be identified by observing the outcome of contests over
resources or by identifying the holders of resources directly (e.g. the male
with the largest harem is by definition the alpha male).
II. "Peck-order" after SCHJELDERUPp-EBBE (1922): if A pecks at Band B
never or seldom reciprocates then A is dominant to Band B is subordi
nate to A (SCHJELDERUPp-EBBE, 1922; ALLEE, 1938). A is the despot and B
is typically afraid of it, adds SCHJELDERUPp-EBBE (1922). According to the
original descriptions of the way in which dominance relationships
develop (SCHJELDERUPp-EBBE, 1922; ALLEE, 1938), dominance implies
that individuals recognize each other. Dyadic dominance status is
assessed on the basis of one agonistic interaction type, namely pecking,
and refers to its consistent, unidirectional pattern over time.
12. "Modified peck-order definition": a slight modification of the "peck
order" definition is to include more than one agonistic interaction type in
the assessment of dominance status. BARRETTE & VANDAL (1986)
rephrased the "peck-order" definition of dominance summarizing its
essence: dominance is an attribute of a relationship between two individ
uals, whenever an asymmetry in the outcome of agonistic interactions is
measured. If a dominant seldom has to fight to supplant a subordinate,
the subordinate is repelled without a need to escalate, then a true domi
nance relationship exists. HAND'S (1986) social dominance relationships
between individuals who meet repeatedly corresponds to this definition.
In agonistic dominance relationships the directionality of the agonistic
encounters is not dependent upon location, as opposed to territoriality
(KAUFMANN, 1983). In order to explain this dominance pattern it has been
290 CARLOS DREWS
argued that one member of the dyad in question consistently submits at
the onset of any encounter as a function of the past history of interactions
with the other member (BERNSTEIN, 1981). Consequently, it may be
assumed that the subjects discriminate between different opponents. A consistent change in the response pattern of two individuals in agonistic
conflicts, following their first contest, indicates that a relationship
between the subjects has been established. The defeated member of the
dyad submits or emits a terminating response in subsequent encounters
with the other member without escalation. On the basis of such a change
from symmetric to asymmetric initial responses in subsequent agonistic
interactions, dyads with a dominance relationship can be differentiated
from those without, since in the latter case each encounter is contested
before yielding. The investigator should not assume that a dominance
relationship exists in each dyad, because unresolved or egalitarian rela
tionships may exist (BOYD & SILK, 1983; HAND, 1986). In summary, the
"modified peck-order definition" is characterized by i) asymmetry in the
outcome of diverse agonistic interactions, ii) avoidance of escalated
encounters mediated by the subordinate's deferring behaviour, and iii)
influence of past encounters on subsequent responses to opponents. The
latter point implies that discrimination on the basis of individual identity
is a necessary element of dominance relationships.
Dominance definition based on theoretical constructs.
The theoretical approach to the study of dominance was introduced by
HINDE (1978) and GAGE (1981) who postulate that dominance must
represent a collection of observable actions, the validity of which can be
empirically verified. The inter-correlation between the observables deter
mines the definition and usefulness of the term or else justifies its
rejection.
13. "Intervening variable": dominance is postulated in theory as an
intervening variable between independent variables and a set of depen
dent variables which are intercorrelated and covary equally in the major
ity of dyads (HINDE, 1978; HINDE & DATTA, 1981). Experience, for exam
ple, influences the direction of agonistic interactions via the intervening
variable "dominance". A dominance/ subordinance relationship implies
THE CONCEPT AND DEFINITION OF DOMINANCE 291
one in which aggression is reduced or (overtly) absent. The pattern of
asymmetry in the various interactions, including non-agonistic ones, may
vary according to the situation. HINDE (1978) uses the term "agressive
dominance" as a subcategory of dominance, to which other, non-agonis
tic, interactions may be related. If aggression and non-agonistic behav
iour are correlated, then both can be considered to be under the influence
of dominance. The "intervening variable" definition is also used by
BAENNINGER (1981), CANDLAND & HOER (1981), and GAGE (1981), among
others.
General attributes of dOininance definitions
There is general agreement about some potentially confounding terms
which should not be equated to dominance. Dominance does not imply
leadership (ALLEE, 1938), and, thus, it is not to be confounded with
"control" (HINDE, 1978): e.g. in baboon (Papio cynocephalusi consortships,
the female may be controlling many aspects of the male's behaviour such
as the direction of movement, while the male remams dominant to the
female.
The association between dominance and aggression differs widely
between the different definitions of dominance (Table 1). Dominance is
generally associated with conflict resolution during agonistic encounters.
The "privileged role" definition of dominance is an exception, in which
status assignement is independent of any agonistic encounters. Fig. 1
shows the minimum set of options encountered on the way to a definition
of dominance which refers to agonistic behaviour. Each possible pathway
in the flowchart leads to a different definition.
'When agonistic encounters are the basis to determine the directionality
of the relationship, definitions of dominance differ with regard to the
expression of overt aggression shown during conflict resolution. In some
definitions overt aggression is the diagnostic feature of a dominance
system. Other definitions do not discriminate between non-aggressive
and escalated dominance interactions and pool all agonistic encounters to
determine status. Yet other definitions explicitly limit the applicability of
the dominance concept to those instances in which conflict resolution
does not include overt aggression or escalated fights (Table 1). In "peck
order" definitions, overt aggression by the dominant individual may be
292 CARLOS DREWS
TABLE 1. Attributes of common definitions of dominance
Ernpdr-ica! observation definitions
Non-agonistic behaviour: Dominance as a role description: - "privileged role"
Agonistic behaviour as part of definition: - "reproductive status" Dominance as a property of the individual: - "dominance is aggressiveness" - "dominance is a trait that conveys rank" Dominance as an attribute of dyadic encounters: - "winner is dominant, loser is subordinate" - "successful combatant" - "priority of access to resources" - "dominance is lack of aggressiveness"
Consistent outcome of dyadic interactions: - "consistent winner of agonistic contests" - "consistent winner at a given context"
Escalation usually avoided: - original "peck-order" - "peck-order" modified
this study -> - essence of dominance
Theoretical construct definition: - "intervening variable"
Attributes
S, P, LD, NT
S/F, (AG), LD, NT
S, AG, LD, IH
S, AG, LD, IH NT S, AG, LD S, AG, LD F, (AG), (ASY), HD S, AG, P, HD S, AG, ASY, HD
S, AG, ASY, HD S, AG, ASY, IR, P, HD S, AG, ASY, IR, P, HD S, AG, ASY, P, HD
AG, NI, HD/LD
S = structural definition, F = functional definition, AG = pattern of agonistic interactions reflects dominance, ASY = asymmetric outcome of contests within a dyad, TR = individual recognition involved, IH = dominance inheritable, NI =dominance not inheritable, P = "peaceful" (no overt aggression during conflict resolution), brackets ( ) = not a necessary condition. LD = low descriptive value, HD = high descriptive value.
the start of an interaction but contests are generally not escalated, given
the default yielding response of the subordinate. These definitions are
included among those in which conflict resolution is usually a "peaceful"
event.
While some definitions consider dominance to be an attribute of the
individual ("dominance is aggressiveness" or "a trait that conveys rank"
definitions), others view dominance as an attribute of dyadic relationships
or of single interactions. Under definitions which do not regard domi
nance as a relationship between individuals, dominance status within
dyads is assigned on the basis of the outcome of a single contest or the
subjects are ranked according to the ratio of individuals defeated to
individuals lost to. Conversely, under those four definitions which regard
dominance as an attribute of a relationship between two individuals,
293 THE CONCEPT AND DEFINITION OF DOMINANCE
IBASIS: AGONISTIC BEHAVIOUR
~ ~
DEFINITION AS THEORETICAL CONSTRUCT
F1JNCTIONAL STRUCTURAL
I V
ESCALATED CONTESTS INCLUDED OR EXCLUDED FROM DEFINITION
v v
OUTCOME OF ONE CONTEST CONSISTENT OUTCOME FROM SEVERAL IS SUFFICIENT CONTESTS BETWEEN SAME INDIVIDUALS
CONTEXTS
RELATIONSHIP
v
EACH CONTEXT TREATED SEPARATELY
OBSERVED PATTERN OF INTERACTIONS CALLED DOMINANCE
DOMINANCE DEFINITION
Fig. I. Flowchart illustrating points of decision when dominance definitions related to agonistic behaviour are formulated.
294 CARLOS DREWS
dominance status is assigned on the basis of the outcome of several
conflicts, if a consistent asymmetry in favour of one dyad member is
observed (Table I). The dyadic asymmetry in contest outcome is a
possible, but not necessary element of the "priority of access to resources"
definition.
The asymmetry in the direction of the outcome of contests arises from
one individual consistently winning and the other consistently losing
consecutive encounters. Ideally, status assignment should only be made in
those dyads in which the asymmetry is statistically significant over a set
period of time. A dominance relationship is just one possible relationship
between two individuals. There are unresolved and egalitarian relation
ships in which there is no clear asymmetry in the outcome of contests
(HAND, 1986). A dominance relationship between individuals, thus
implies that the same individuals meet and resolve conflicts on several
occasions (HINDE & STEVENSON-HINDE, 1976) in a clearly unidirectional
pattern.
The word "relationship" is ambiguous in the context of dominance
definitions. A dominance relationship can be understood as a mental
experience of the individuals concerned. This view has been criticized by
ALTMANN (1981) and is associated with those definitions of dominance
which imply that individual recognition operates during interactions (e.g. "peck-order" definitions). A simpler use of the term "relationship" refers
strictly to data, to the interaction between the role of winner and loser
among two individuals during a series of agonistic encounters. The latter
use corresponds to the "consistent winner of agonistic encounters" and
"the consistent winner at a given context" definitions.
Some advocates of dominance as an attribute of dyadic relationships
have argued that dominance presupposes individual recognition (e.g. WYNNE-EDWARDS, 1962; ROWELL, 1974; HINDE & STEVENSON-HINDE,
1976). Past conflicts may influence the outcome of future encounters (e.g. mice Mus sp.: GINSBURG & ALLEE, 1942; rhesus monkeys Maraca mulatta:
ROSE et al., 1972, 1975). Individual recognition, however, is not a neces
sary condition to explain those cases in which one individual consistently
submits to another, familiar individual without an escalated fight taking
place. At the onset of each conflict the opponents may assess one another
on the basis of a morphological feature or display which correlates well
with competitive ability (KODRIC-BROWN & BROWN, 1984) regardless of
----------
295 THE CONCEPT AND DEFINITION OF DOMINANCE
past experiences with the same opponent. This pattern of "peaceful"
conflict resolution corresponds to the "dominance is lack of aggressive
ness" definition. Individual recognition and memory of past encounters is
an important ability when such predictive cues are not available and
fighting ability can only be assessed in escalated contests or inferred from
observation of the opponent's behaviour towards other, known members
of the social group.
In conclusion, individual recognition is not a necessary condition to
produce the behavioural pattern observed under any of the dominance
definitions, although advocates of the "peck-order" definition envision
dominance as an identity relationship between two individuals. The
hypothesis that individuals use individual recognition in their assessment
of contest success has to be tested in each particular case.
Domdrrarrce and heritability
Dominance can only be inheritable when it is a property of individuals
(Table 1). Several breeding studies claim to have selected particularly
dominant individuals or to show that dominance status has an inheritable
component (e.g. Nlo0RE, 1990; DEWSBURY, 1990; and references therein).
An investigator can successfully breed for dominant individuals on the
basis of the "dominance is aggressiveness" definition. Aggressiveness has
been shown to have an inheritable component in several species (e.g. chickens, Gallus domesticus: GUHL et al., 1960; dogs, Canisfamiliaris: SCOTT
& FULLER, 1965; sticklebacks, Gasterosteus aculeatus: BAKKER, 1986; sil
vereyes, Zosterops lateralis: KIKKAWA et al., 1986; fruit flies, Drosophila
melanogaster: HOFFMANN, 1988). On the other hand, breeding experiments
suggest that there is a genetic component to the determinants of rank,
when dominance is defined as an attribute of relationships (DEWSBURY,
1990).
Explicit definition of dominance and careful formulation ofthe conclu
sions of breeding experiments are essential to avoid misunderstandings
about the heritability of dominance. Claims regarding the heritability of
dominance traits are bound to evoke criticism by the advocates of domi
nance as an attribute of conflict resolution and of dominance as a descrip
tion of role. Dominance as an attribute of an interaction or of a relation
ship between two individuals is a relative measure which cannot be
296 CARLOS DREWS
selected for (GARTLAN, 1968; ROWELL, 1974; BERNSTEIN, 1981; BARRETTE,
1987). Natural selection operates on absolute, competitive properties of
individuals and not on relative dominance status. Dominance ranks
depend on the group composition and are, therefore, not an inheritable
property of an individual either (DUNBAR, 1988). Dominants and subordi
nates behave differently, but these are not genetically distinct roles, or
genetically fixed alternative strategies, since subordinates are fully capa
ble of behaving as dominants given the appropriate circumstances for a
change in status (MCGUIRE et al., 1984). Furthermore, most individuals in
a hierarchy are simultaneously subordinate to some and dominant to
other members of the group. The issue of the heritability of dominance
illustrates how a given definition of dominance may have applications
which are incompatible with other definitions of the term.
Descriptive, predictive and explanatory value of dominance
One limitation of definitions based on observations rather than theory is
that these are not open to empirical investigation. If another definition is
proposed, there is no methodology to determine which of the definitions
is appropriate and the question remains one of semantics rather than
science (GAGE, 1981). Nevertheless, criteria such as the descriptive, pre
dictive and explanatory value can be used to differentiate between
definitions.
The descriptive value of dominance.
Dominance has a high descriptive value when its definition refers to
something for which no other single term existed before and the term is
useful when it can be used to differentiate that something from something
else. In addition, dominance can be used as a descriptive tool to test the
possibility of merging, and hence simplifying, categories of behaviour
(CANDLAND & HOER, 1981). Thus, the descriptive value of a dominance
definition is high if it serves efficiently the process of categorization. The
descriptive value is an absolute property of a definition, irrespective of the
theoretical context in which it is used. Contrary to some contentions
(BERNSTEIN, 1981; HINDE & DATTA, 1981), the descriptive value of a
dominance definition may justify keeping the definition without it being
predictive or explanatory. Neither the predictive nor the explanatory
297 THE CONCEPT AND DEFINITION OF DOMINANCE
value are inherent absolute qualities of the definition but rather a func
tion of the theoretical context in which the concept is used and of the
questions asked. In assessing the usefulness of the dominance concept,
one can first estimate its descriptive value, then test empirically whether
the definition is supported by the data, and lastly assess the explanatory
value of using the concept for a particular question.
In the following definitions, dominance has a low descriptive value
because it is used as a synonym of other, already existing terms, such as
aggressiveness, winner, or an arbitrarily chosen status or role: "domi
nance is aggressiveness", "winner is dominant, loser is subordinate",
"successful combatant", "reproductive status", and "the privileged role"
definition. The use of dominance following these definitions does not help
to describe, predict or explain any phenomena better than do its syn
onyms. SYME (1974) argued, with respect to context specific asymmetries
in the outcome of agonistic interactions, that if each group has a large
number of "dominance orders" then the concept is effectively useless. An
asymmetry in the outcome of particular interactions is not a sufficient
justification to introduce a dominance concept, either as a descriptive
tool or an explanatory mechanism (DREWS, 1973; SYME, 1974).
The "dominance is a trait that conveys rank" definition is used to
collectively refer to all those behavioural characteristics of an individual
which are decisive in the outcome of an agonistic conflict. Dominance in
this sense has a high descriptive value. Dominance definitions which
include consistency in the direction of the outcome of dyadic contests
and/or lack of aggressive escalation during conflict resolution, also have a
high descriptive value in that they describe formerly unrecognized
phenomena.
In general, the functional definition of dominance, i.e. "priority of
access to resources", describes the access to resources mediated by ago
nistic contests. Por-e & DEVORE (1979) refer more specifically to the
pattern of context specific access to resources. This definition equates
dominance with non-egalitarian access to resources, and consequently
has a high descriptive value since there was no other term to dennote that
phenomenon.
Dominance in theory language is a hypothetical construct to investi
gate the common denominator of certain categories of behaviour (CAND
LAND & HOER, 1981), and is similar to constructs such as "stress",
298 CARLOS DREWS
"motivation" and "drives" (MAXIM, 1981). Dominance is a useful con
cept because it may enable simplifying our description: by using domi
nance as an intervening variable between independent and dependent
variables, we would reduce the number of links needed to describe the
interaction between both sets of variables (HINDE, 1978). Economy in
description is a first step in explanation (HINDE, 1978). When agonistic
rank has a high predictive value in determining the outcome of other
dyadic relationships, it is useful to abstract dominance as a description of
some aspects of social structure (DEAG, 1977; HINDE, 1978). The descrip
tive value of dominance as an intervening variable is a function of the
inter-correlation between different interaction types and can be tested
empirically. In female primates, for instance, well inter-correlated vari
ables could be "supplants", "grooming", and "submissive", possibly with
a weaker link to "priority of access" (HINDE & DATTA, 1981). We know,
however, that there is lack of consistency even within agonistic categories
since context is likely to influence the pattern observed (Por-r & DEVORE,
1979; LEE, 1983; HAt'lD, 1986). If the dependent variables are unlikely to
be well correlated then, following GAGE (1981), the intervening variable
definition can be rejected. The usefulness of dominance, however, does
not depend on a correlation between dominance order and other aspects
of social behaviour. Dominance is still useful in the description of a
particular type of social structure, in which by some criterion of bossing
related to aggression, the individuals can be arranged in a hierarchical
order (HINDE, 1978).
The predictive value of dominance.
Dominance has a high predictive value when the direction or outcome of
a given interaction can be accurately predicted on the basis of past
observations of dominance behaviour. Dominance is, however, a variable
which remains dynamic and, thus, predictability needs neither to be
perfect nor permanent; ontogeny alone guarantees that physical abilities
vary (BERNSTEIN, 1981). "Prediction" (sensu BERNSTEIN, 1981) alludes to
the degree of confidence with which the statistical asymmetry in dyadic
contests predicts the outcome of any given subsequent conflict within the
same dyad. Cardinal dominance ranks have been calculated on the basis
of the probability of winning contests (BOYD & SILK, 1983). Hence,
299 THE CONCEPT AND DEFINITION OF DOMINANCE
dominance is useful as a shorthand term to indicate that the outcome of
an agonistic interaction between two individuals is predictable with some
practical level of certainty (ROWELL, 1974). "Prediction" can also be used
to refer to the reliability with which the statistical asymmetry in dyadic
contests predicts the direction of other, non-agonistic interactions outside
the context of dominance.
The predictive value of a dominance definition is only of interest,
therefore, when the investigator uses dominance relationships to antici
pate the behaviour of individuals. The level of accuracy of the prediction
is not an attribute of the definition itself but of the behaviour of the study
animals, and the usefulness of such a prediction depends on the questions
asked in each particular case. Accurate prediction alone can be a heuris
tic value of a dominance definition without it being explanatory. This
approach has yielded contrasting results, for some authors claim that
dominance does predict a wide variety of social interactions (e.g. RICH
ARDS, 1974; SEYFARTH, 1976, 1980; CHENEY, 1978) and others point out
the lack of correlation between different measures of dominance (GAR
TLAN, 1968; SYME, 1974; BERNSTEIN, 1981; BRAIN, 1981). Variation in the
definitions of dominance contributes to the discrepancy in such results.
The explanatory value of dominance.
It has been contended that the concept of dominance as an explanation of
behaviour requires that it should actually predict priority of access to
resources at least sometimes (RICHARDS, 1974; DEAG, 1978). This require
ment, though, implies a priori that dominance influences the pattern of
access to resources or else that priority of access to resources be part of
the definition of dominance. Predictions about patterns of resource
access, however, are not necessary for the concept of dominance still to be
explanatory. Dominance has a high explanatory value when the introduc
tion of the term and measurements of dominance reduce the magnitude
of formerly unexplained variance in the data. The explanatory value
arises from finding which variables depend on dominance since, in this
way, dominance improves our understanding of social organization
(BERNSTEIN, 1981). It is difficult, nevertheless, to define which is an
independent measure of dominance and which are its dependent vari
ables (BERNSTEIN, 1981). The explanatory value can be an inherent qual
300 CARLOS DREWS
ity of theoretical definitions of dominance (see next paragraph) but is not
a necessary property of structural definitions. It is rather a function ofthe
theoretical context in which the concept is used and of the questions
asked by the investigator.
With regard to theoretical definitions of dominance, HINDE (1978)
argued that the concept of dominance as an intervening variable has
explanatory value if the following conditions are satisfied: (I) the investi
gation is concerned with more than one dyad, (2) each dyad has a
multiplex relationship involving comparable complementary interactions
in which one bosses the other, and (3) the pattern of inbalance in those
interactions is similar in the different dyads. The usefulness of dominance
increases with the variety of correlations among dependent variables
(HINDE & DATTA, 1981). In contrast, CANDLAND & HOER (1981) argued
that dominance as an intervening variable is a descriptive tool which
serves the process of categorization and is not explanatory. Dominance as
an intervening variable does not make any inferences about the direction
of causality in the observed correlations among dependent variables.
Moreover, dominance as an intervening variable is, by definition, not an
empirical variable. Consequently, it cannot be incorporated into an
empirical model to attempt to improve the fit between predictions and
observations. Thus, dominance as an intervening variable can be a pow
erful descriptive tool but is of low explanatory value with respect to
questions about the nature of the observed behaviour.
The (in)adequacy of dOIninance definitions
Much of the controversy around the concept of dominance has arisen
from the variety of definitions and usages given to the term. Most of the
definitions of dominance are structural and as such, they are all justified
on semantic grounds (GAGE, 1981). Parsimony, however, dictates that
there should be an upper practical limit to the number of new definitions
created for the same term and that their justification should depend on
their descriptive power. Ideally, for the concept to be more useful and to
reduce ambiguity, all users of dominance should refer to one and the
same phenomenon. In the following discussion I evaluate the adequacy of
the dominance definitions listed above and synthesize the essence of a
unitary dominance concept for behavioural studies. The criteria used to
301 THE CONCEPT AND DEFINITION OF DOMINANCE
categorize the definitions into appropriate and less appropriate are their
respective descriptive values and their affinities to the original definition
of dominance as described by SCH1ELDERUPp-EBBE (1922). The original
definition is not only taken as a reference because it happens to be the
first definition, but also because it has a high descriptive value and called
our attention to a distinct behavioural phenomenon. It is noteworthy that
in view of the controversy around dominance definitions, SADE (1981)
suggested to look back at the early literature on dominance, which is clear
and straightforward in the definitions and use of the concept (e.g. ALLEE,
1938; COLLIAS, 1944).
Most definitions of dominance listed above, including the original
"peck-order" definition, have in common that they refer to agonistic
behaviour. Dominance should be reserved to its already widely estab
lished use for patterns of interaction, in which the direction of comple
mentarity is initially established through aggression, andfor in which
aggressive behaviour is potentially present (HINDE, 1978). Its usefulness
should not be diluted with other cases of complementarity in interactions,
e.g. as referred to by WILSON (1975) with respect to food passage in honey
bees. For this reason, as well as because of their low descriptive value, the
"privileged role" and the "reproductive status" definitions of dominance
are inadequate. Also, those definitions which refer to dominance as a
synonym of aggressiveness, winnerfloser or "successful combatant" are
inadequate on the basis oftheir low descriptive value. Dominance should
not be defined as a synonym of any other already existing term.
BAENNINGER (1981) understands dominance as a trait which combines
several different intercorrelated variables (see HINDE, 1978), and explic
itly defines dominance as a property of individuals. Similarly, WILSON'S
(1975) mention of dominance as equivalent to aggressiveness implies that
dominance is a variable, individual trait. Definitions of dominance as a
trait of individuals ("dominance is aggressiveness", "dominance is a trait
which conveys rank") are incompatible with those definitions which
regard dominance as an attribute of dyadic encounters or relationships,
including SCH1ELDERUPp-EBBE'S "peck-order" definition.
Discontent with the "dominance is aggressiveness" definition has been
emphasized by several authors. It is generally agreed that dominance
refers to the patterning of interactions between individuals and not to the
amount of aggressive behaviour that they show (e.g. JAY, 1965;
302 CARLOS DREWS
KAUFMANN, 1967; CHALMERS & ROWELL, 1971; ROWELL, 1974; SYME,
1974; BERNSTEIN, 1976; 1981; HINDE, 1978). Rather, aggression can be
viewed as an expression of dominance (BERNSTEIN, 1976). Whilst domi
nance may depend on aggression or potential aggressiveness, it does not
necessarily correlate with them (LOCKWOOD, 1979; BERNSTEIN, 1981). In a
principal factor analysis of wolf (Canis lupus) behaviour, the absolute level
of agonistic behaviour was not part of the dominance factor detected
(LOCKWOOD, 1979). The results of a dominance and communication
analysis in children support the theoretical conception of dominance, that
emphasizes the relationship between individuals rather than the coercive
behaviour of some group members (CAMRAS, 1984).
Although aggressiveness is known to vary between individuals (e.g. CUHL et al 1960), the levels of aggression observed in natural agonistic
contests do not necessarilly reflect these differences. The game theoretical
approach to the study of aggressive competition (e.g. PARKER, 1974;
CARYL, 1980; MAYNARD-SMITH, 1982; ENQUIST & LEIMAR, 1990) suggests
that all individuals have the potential to express aggression, but that the
aggression observed is a circumstantial product of the cost/benefit ratio
of using it. Hence, the directionality of aggression commonly used to
assign dominance status is not necessarilly related to an aggressive prop
erty of the individuals concerned, but rather to the fact that some individ
uals defer upon being attacked because their chances of winning a given
contest are low. A definition of dominance based on the outcome of
several dyadic conflicts relates more to SCHJELDERUPp-EBBE'S (1922)
"peck-order" definition than the "dominance IS aggressiveness"
definition.
In the previous paragraphs, those definitions of dominance were con
sidered inadequate which were not related to agonistic interactions at all,
had a low descriptive value because they referred to dominance as a
synonym of an already existing term, and/or described dominance as an
inherent attribute of individuals rather than of interactions between
them. Those definitions which refer to dominance as an attribute of
conflict resolution patterns (Table I) are now discussed, bearing in mind
that SCHJELDERUPp-EBBE'S definition is characterized by the asymmetry in
the outcome of dyadic encounters and the fact that conflicts are generally
resolved by the deference of the loser without escalation. The only defini
tions which regard asymmetry and lack of escalation as necessary ele
303 THE CONCEPT AND DEFINITION OF DOMINANCE
ments of dominance are the original "peck-order" definition and the
"modified peck-order definition". Definitions which consider one of these
conditions as necessary include the "dominance is lack of aggressiveness"
(lack of escalation), "consistent winner of agonistic contests" (asym
metry), and the "consistent winner at given contexts" definition (asym
metry). Asymmetry and lack of escalation mayor may not be given in the
conflicts considered in the "priority of access to resources" definition,
which, thus, departs more noticeably from the "peck-order" definition.
The "priority of access to resources" definition of dominance has been
subject to criticism (e.g. SVME, 1974; BERNSTEIN, 1981; BARRETTE & VAN
DAL, 1986). Attention on advantages to dominants leads to frame a
definition of dominance based on priority of access to incentives, while
ignoring structure in favour of consequences (BERNSTEIN, 1981). Such
functional definitions are problematic when different strategies yield
similar benefits (examples in BERNSTEIN, 1981). If dominance is measured
on access to only some, specific incentives it is then of no explanatory
value to understand the principles of social organization.
The use of the "priority of access to resources" definition is oflimited
value to the study of dominance, because dominance more generally
refers to all conflict resolution instances, while not all conflicts are over
resources (HAND, 1986). Further, studies using the "priority of access to
resources" definition of dominance sometimes claim to describe an effect
of dominance on resource access, a circular statement which arises from
measuring dominance on the basis of the pattern of resource access (e.g. GAUTHREAUX, 1978; SVME, 1974; ApPLEBV, 1980). This functional defini
tion is, hence, inadequate to study whether high dominance rank per se is
advantageous. The interpretation of an aggressive order must be
restricted to aggressive behaviour unless it can be correlated with a
quantitative demonstration of general priority of access to resources
(SVME, 1974). In addition, when measuring dominance on the basis of
access to incentives, there is sometimes the problem of identifiying what
are incentives (BERNSTEIN, 1981). The constraints of the "priority of
access to resources" definition illustrated above, nevertheless, do not
make it less valid with respect to the "peck-order" definition. The "prior
ity of access to resources" definition, however, is concerned with a
particular kind of interaction, namely contests over resources, irrespec
tive of a dyadic consistency in their outcome and of the degree of
304 CARLOS DREWS
escalation involved. For this reason, this definition is incompatible with
respect the dominance concept of SCH]ELDERUPp-EBBE (1922). A similar
argument applies to the "intervening variable" definition, which also
lacks affinity with the original definition of dominance.
Few authors have objected to the "peck-order" definition. HINDE &
DATTA (1981) argued that if dominance/ subordinance is assessed in terms
of only one dependent variable (here: pecking), then dominance is merely
descriptive and has no explanatory value. Dominance would be merely a
way of describing the data in other words. I argued above that the
explanatory value is not a property of the definition but of the context in
which it is used. Clearly, the original definition was concerned with only
one kind of interaction, namely pecking, which would limit its appli
cability to other taxa. The "modified peck-order definition" includes
other complementary agonistic interactions in an analogous way to
SCH]ELDERUPp-EBBE'S treatment of pecking. This modified definition also
derives its high descriptive value from referring to dominance as a consis
tent pattern in dyadic interactions whereby deference rather than esca
lated fights are the rule, a phenomenon which deserves a description on
its own. Memory and individual recognition are implicit in the "peck
order" definition as proximate mechanisms to explain the deference
behaviour. These mechanisms may apply in some cases but need not be
necessary for the consistent deference behaviour to be observable. Mech
anisms and function should not form part of the definition and used
instead within hypotheses concerning the causation of dominance
relationships.
The feature recognition criterion and dODlinance relationships
Broad definitions of dominance do not preclude the study of dominance
across different sizes, sexes and age categories, and even between groups,
populations or species (e.g. GAUTHREAUX, 1978). SEYFARTH (1981) argued,
however, that it makes little functional sense to lump together all age-sex
classes in studying dominance, because we know about the variety of
different selective presures acting on each class. If the outcome of contests
can be predicted by location (territoriality) or a relational attribute which
correlates with the direction of outcomes (e.g. size, age, sex) then it is not
useful to describe each of them as a special type of agonistic dominance
305 THE CONCEPT AND DEFINITION OF DOMINANCE
(BERNSTEIN, 1981). Such a view tacitly implies that dominance relation
ships exist as long as the investigator does not identify one single reliable
predictor of contest outcome. From this perspective, dominance relation
ships reflect the investigator's ignorance about the identity and interrela
tion of determinants of conflict outcomes and dominance would cease to
exist when these are understood. This example emphasizes the impor
tance of explicitly specifying exactly how dominance is defined (or per
ceived) by each investigator. However, if dominance is viewed as the
consistent asymmetry in the outcome of contests between two individuals
whereby the subordinate generally defers to the dominant without escala
tion, then identifying the determinants of this pattern is a necessary step
towards explaining it and no identified determinant should invalidate the
phenomenon.
In a rigorous application of the "peck-order" definition of dominance,
memory of past encounters and individual recognition determine the
behaviour in dominance dyads. Such a definition implies a relationship
between each of two individuals and thus, it refers to dominance as a
much more specific phenomenon than just asymmetrical outcomes in
non-escalated contests within a dyad. When observed agonistic patterns
are equivalent to those expected by a peck-order dominance, we need to
know whether identity of the opponent is used to predict the outcome of a
contest, before a peck-order dominance relationship is inferred. This
question can be approached by witnessing the first contests between
unfamiliar individuals and then observing the corresponding change in
agonistic response over time. In stable social groups, changes in status
suggest that identity recognition may be used by opponents instead of
predictive morphological features when such features do not change as
frequently as dominance status.
ALTMANN (1981) regards dominance relationships as cognitive experi
ences which should be reserved to the higher primates and humans. He
argues that as long as it is not shown that individuals react to a relation
ship, rather than to agonistic behaviour past or present or correlations
thereof, parsimony dictates that relationships need not be inferred. If a
general feature of the opponent (like sex or age) is used at the onset of
each encounter to decide whether the contest should be escalated or
avoided then past experience of the opponent and its identity would be
irrelevant. The feature-recognition criterion is probably used during most
306 CARLOS DREWS
dominant/ submissive interactions between individuals which meet only
once, as explained in the "dominance is lack of aggression" definition.
BERNSTEIN (1981) regards the dominant individual as taking an active
part in the dyadic dominance relationship when it acknowledges immedi
ate submission rather than attacking. There is no need to postulate an
identity relationship on that ground, if the dominant individual follows
the simple rule of not attacking when the opponent submits immediately
(a behavioural feature). Por-r- & DEVORE (1979) discuss the adaptive value
of stopping further attack once the opponent has submitted, in contexts in
which a relationship between the two individuals is irrelevant.
Individuals, sex, groups, or species: the units of domfrrarrce
The concept of dominance has been mostly utilized to characterize the
behaviour of individuals. It has been also applied to the relationship
between categories such as sexes, groups, and species. The working
hypothesis in studies of intersexual dominance (e.g. RALLS, 1976;
DESROCHERS et al., 1988) is that one sex may exclude the other from
limiting resources. Such an exclusion is referred to as dominance, resem
bling the "priority of access to resources" functional definition. Domi
nance is not to be interpreted as the agent causing resource monopoliza
tion because dominance is measured on the basis of the outcome of all
agonistic encounters, most of which may be over resources. Dominance
in this context is descriptive, not explanatory.
Intergroup dominance is similar to the dominance relationships in
dyads of familiar individuals, because in intergroup contests often the
entire group behaves as a unit which is known to the opponent group
from previous encounters. Intergroup dominance in wild rhesus monkeys
has been described on the basis of supplants, avoidance, or fights between
groups (SOUTHWICK et al., 1965). This usage of the term corresponds, at
the group level, to the "consistent winner of agonistic contests"
definition.
Interspecific dominance after MORSE (1974) is the priority of access to
resources that results from successful attacks, fights, chases or supplanting
actions present or past. It represents one mechanism of interference
competition. For example, gulls (Larus sp.) dominate curlews (Numenius
arquata), while curlews dominate small waders (ENS et al., 1990). ~WAGNER
307 THE CONCEPT AND DEFINITION OF DOMINANCE
& GAUTHREAUX (1990) refer to MORSE'S (1974) definition as the definition
of dominance in general. GAUTHREAUX (1978) discussed the ecological
significance of interspecific dominance following the "priority of access to
resources" definition. Other claims that the concept of dominance can be
applied to groups, populations and species (VVILSON, 1975) have referred
to the "winner is dominant, loser is subordinate", or the "dominance is
lack of aggression" definitions. Such definitions were shown above to be
inadequate at the level of individuals, and the same reasoning applies to
their application to units of higher order.
A further problem of applying the concept of dominance to interactions
outside the familiar social group is that this use is not compatible with
definitions of the term that imply a relationship between the interactants.
Advocates of the latter definition argue that dominance hierarchies are
only possible in small groups because individual aquaintance is a prereq
uisite (WYNNE-EDWARDS, 1962; ROWELL, 1974). In the usage of domi
nance beyond the confines of the familiar group, the individual identity of
the opponent and past agonistic experiences with that particular individ
ual are often irrelevant to the decisions of the contestants. In interspecific
dominance interactions the dyadic conflict is probably settled by recogni
tion of species specific attributes of the opponent.
The crucial criterion to justify the use of dominance for higher order
categories is not the choice of category, but rather the definition of
dominance used. When dominance is used beyond the level of dyadic
interactions between single conspecifics there is the danger that analogies
of dominance will be confused with homology (BERNSTEIN, 1981).
The essence of d orrri'narrce i synthesis and definition
Despite a great variety of dominance definitions, it is generally agreed
that dominance refers to agonistic behaviour. Several definitions of domi
nance were rejected on the grounds of their low descriptive value. The
original definition of dominance by SCHJELDERUPp-EBBE (1922) described
a distinct phenomenon in chicken, which is regarded here as the basis for
a more general concept of dominance with broader applicability. The
high descriptive value of this dominance concept justifies its use; predic
tion and explanation are applications of dominance, which originate in
the particular field of interest of each investigator. The essence of domi
308 CARLOS DREWS
nance which emerges from the above discussion IS summarized in the
following, structural definition of the term:
Dominance is an attribute of the pattern of repeated, agonistic interac
tions 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.
Operational definitions of dominance, based on the above definition, can
be formulated in each particular study according to the choice of subjects
and the theoretical framework used. Although this definition concen
trates on dyadic interactions (because these are readily observable), it
does not preclude the possiblity that the outcome is influenced by the
nearby presence of other individuals, which may tacitly or overtly support
one of the contestants (see KAWAI (1958, 1965) for an introduction to the
concept of dependent rank).
A semantic clarification complements this definition: dominance status
and dominance ranks are different measures (HINDE, 1978; BERNSTEIN,
1984; BARRETTE & VANDAL, 1986; DUNBAR, 1988). This distinction
applies to the definitions of dominance which refer to the pattern of
dyadic encounters (Table 1). Dominance status refers to a relationship
between two animals and depends on an animal's attributes compared to
those of the other, while rank refers to the relative position within a group
and, hence, depends on group composition. Dominance status refers to
the status of one individual within a given dyad and can be either
dominant or subordinate according to the direction of the statistically
significant asymmetry in the outcome of several contests. Dominance
rank refers to the position of one individual in a dominance hierarchy and
can be expressed at an ordinal level either numerically, in greek letters (a = top rank, Q = bottom rank, SCHJELDERUPp-EBBE, 1922) or qualitatively
as high or low, but not as dominant or subordinate.
In general, dominance ranks are calculated after assessment of domi
nance status in all possible dyads of the group. The resulting hierarchy
can be linear, but does not necessarilly have to be so (ApPLEBY, 1983).
Dyadic dominance/ subordinance relationships and the dominance hier
archy are not necessarily related and the first does not imply the existence
309 THE CONCEPT AND DEFINITION OF DOMINANCE
of the other in a social group (HINDE, 1978). The limitations of ordinal
ranks, in which by definition the distance between adjacent ranks is the
same, have lead some investigators to develop indices which reflect the
more realistic "dominance distances" that separate animals in a hier
archy (e.g. BOYD & SILK, 1983; ARCESE & LUDWIG, 1986; ZUMPE &
MICHAEL, 1986; DREWS, in prep.).
With respect to the above definition, dominance has been viewed from
different perspectives. At a general level dominance is seen as a descrip
tive tool (e.g. CANDLAND & HOER, 1981). ALTMANN (1981) and SEYFARTH
(1981) maintain that dominance relationships and dominance hierarchies
have no function and are not ends in themselves or cognitive experiences
of the animals, but simply shorthand, structural descriptive terms used by
the observer. BERNSTEIN (1981) argued that dominance can be regarded
as a relative measure used to illustrate one attribute of a dyadic relation
ship. SMUTS (1981) sees dominance relationships as a useful estimate of an
individual's ability to influence the behaviour of another for its own
benefit, through that individual's power to inflict physical injury. Por-t- &
DEVORE (1977) view agonistic dominance as an unavoidable product of
cost/benefit considerations during competitive interactions. They, conse
quently, frame dominance under the theory of games for aggressive
competition.
Other investigators concentrate on the fact that escalated fights are
generally avoided and regard dominance as a dimension ofthe communi
cation system (e.g. CHANCE, 1956; MAXIM, 1981). The subordinate may
signal defeat before the dominant completes the attack or immediately
when intention to attack is signaled by stereotyped movements or vocaliz
ations. This is seen as evidence that a communication system has evolved
(SADE, 1981). The lack of agreement in the way that investigators perceive
dominance is evident, and preference for one interpretation or the other
is bound to remain arbitrary.
The structural definition proposed above simplifies the debate around
the dominance concept because it makes no assumptions about the men
tal experiences of the subjects or about those of us investigators who use
the concept. This definition provides a frame for future studies on domi
nance which can deal with more specific aspects, such as the role of
memory and individual recognition, as well as the identification of deter
minants and consequences of dominance status.
310 CARLOS DREWS
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