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Counter aggression and reconciliation in Assamese macaques (Macaca assamensis).

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American Journal of Primatology 56:215–230 (2002)
Counter Aggression and Reconciliation in Assamese
Macaques (Macaca assamensis)
MATTHEW A. COOPER* AND IRWIN S. BERNSTEIN
Department of Psychology, University of Georgia, Athens, Georgia
Patterns of aggressive and affiliative behavior, such as counter aggression and reconciliation, are said to covary in the genus Macaca; this is
referred to as the systematic variation hypothesis. These behavior patterns constitute a species dominance style. Van Schaik’s [1989] socioecological model explains dominance style in macaques in terms of withinand between-group contest competition. Dominance style is also said to
correlate with phylogeny in macaques. The present study was undertaken to examine phylogenetic and socioecological explanations of dominance style, as well as the systematic variation hypothesis. We collected
data on counter aggression and reconciliation from a habituated group of
Assamese macaques (Macaca assamensis) at the Tukeswari Temple in
Assam, India. The proportion of agonistic episodes that involved counter
aggression was relatively low. Counter aggression, however, occurred more
often among males than among females, and it was most common when
females initiated aggression against males. The conciliatory tendency for
this group of Assamese macaques was 11.2%. The frequency of reconciliation was low for fights among males and for fights among females, but
reconciliation was particularly rare for opposite-sexed opponents. Female
social relationships were consistent with the systematic variation hypothesis, and suggest a despotic dominance style. A despotic dominance style
in Assamese macaques weakens the correlation between dominance style
and phylogeny in macaques, but it is not inconsistent with the socioecological model. Male–female relationships were not well explained by
the despotic-egalitarian framework, and males may well have more tolerant social relationships than do females. Sex differences need to be
considered when categorizing species according to dominance style. Am.
J. Primatol. 56:215–230, 2002. © 2002 Wiley-Liss, Inc.
Key words: Macaca assamensis; reconciliation; counter aggression;
dominance style; sex differences
Contract grant sponsor: National Geographic Society; Contract grant number: 5862-97.
*Correspondence to: Matthew Cooper, Center for Brain Science and Health, Georgia State University, 24 Peachtree Center Ave. NE, Atlanta, GA 30303. E-mail: biomcc@langate.gsu.edu
Received 28 February 2000; revision accepted 30 January 2002
DOI: 10.1002/ajp.1076
Published online in Wiley InterScience (www.interscience.wiley.com).
© 2002 Wiley-Liss, Inc.
216 / Cooper and Bernstein
INTRODUCTION
Dominance is recognized by an asymmetry in the pattern of aggression and
submission in agonistic encounters [Bernstein, 1981]. Physical abilities and social skills both influence dominance relationships. Consequently, dominance hierarchies are rarely perfectly linear. Even among macaques, where dominance
relationships are pervasive, subordinates contest aggression in a variety of species (M. arctoides [de Waal & Luttrell, 1989], M. mulatta [Bernstein & Ehardt,
1985], M. nigra [Petit et al., 1997], and M. tonkeana [Thierry, 1985]). Bidirectional aggression in some cases may reflect the influence of alliances, testing by
the subordinate, and the process of rank acquisition among immature animals.
Bidirectional aggression may also indicate social tolerance. For example, bidirectional aggression has been related to a lower intensity of aggression and less
exclusion around a limited water source [Thierry, 1985; de Waal & Luttrell, 1989].
If dominants are forced to “tolerate” subordinates when they are physically incapable of preventing the subordinates’ retaliation, their “social tolerance” is not
tolerance at all. Alternatively, a dominant animal may tolerate insubordination
from valuable social patterns such as kin, grooming partners, sexual partners,
alliance partners, or individuals that aid against an external enemy, such as
another group or predators.
Social tolerance is related not only to the frequency of bidirectional aggression, but also to the intensity of aggression, the expression of reconciliation, kin
biases in affiliative behavior (such as grooming), and patterns of agonistic aiding
and infant care [Thierry, 2000]. In despotic societies, subordinates should readily
submit and rarely contest clumped resources. Affiliative relationships among dominants and subordinates should be weak, and reconciliation rare. Animals may
affiliate and form alliances with kin, and mothers should be restrictive with their
offspring. In species with a more tolerant dominance style, access to resources
should be less strongly linked to dominance rank and subordinate animals should
be less likely to immediately submit. Relationships among dominants and subordinates should permit high levels of affiliative contact and reconciliation. Social
bonds with kin may be less important, and mothers should be less restrictive.
These behavior patterns should covary and constitute a species’ dominance style
(the systematic variation hypothesis) [Thierry, 2000; Castles et al., 1996; de Waal
& Luttrell, 1989; Thierry, 1985]. These behavior patterns are interrelated, so
factors influencing one type of behavior should influence the rest. Cords and
Aureli [2000] suggested that, at least for reconciliation, variation depends on the
value, security, and compatibility of the relationship.
While the systematic variation hypothesis predicts the covariation of behavior that comprises dominance style, two theories have been proposed to explain
interspecies variation in dominance style. Van Schaik’s [1989] socioecological hypothesis states that the distribution of resources influences the form of resource
competition [Sterck et al., 1997]. When resources occur in small clumps, and
access within groups is resolved by contest competition, subordinates may learn
to submit immediately to dominant individuals whenever there is any possibility
of an agonistic encounter. This leads to despotic dominance relationships marked
by a high frequency of submissive signaling [de Waal & Luttrell, 1989; Thierry,
1985]. When resources occur in larger clumps, priority of access to incentives
within groups may only sometimes be resolved by contest competition, and between-group competition may become important. In this case, subordinates may
wait for some aggressive signal from a dominant before submitting or withdrawing. This is considered to indicate greater tolerance and less despotic relation-
Counter Aggression and Reconciliation / 217
ships [Preuschoft & van Schaik, 2000]. When resources are not clumped, and
within-group competition is mainly of a scramble variety, then egalitarian relationships should prevail. In this case, subordinates show initial resistance to a
dominant, dominants use milder forms of aggression that do not elicit prompt
withdrawal, or dominance relationships do not exist.
The phylogenetic hypothesis states that closely related macaques will show
similar dominance styles [Matsumura, 1999; Thierry, 2000]. This hypothesis predicts a less immediate effect of ecology. It predicts that dominance styles should
reflect the ecological pressures for greater or lesser contest competition within
and between groups in the niches of the subgenera in the genus Macaca. The
socioecological and phylogenetic hypotheses are not mutually exclusive. While
the socioecological hypothesis advocates the importance of ecological factors that
select for variation in dominance style, the phylogenetic hypothesis stresses the
importance of phylogenetic constraints on the expression of dominance style. No
doubt both ecological and phylogenetic processes are at work.
This study examined the dominance style of Macaca assamensis, the
Assamese macaque. Since M. assamensis belongs to the Sinica group of macaques,
and members of this group are hypothesized to have more tolerant social relationships than members of the Fascicularis group, which includes M. fascicularis,
M. mulatta, M. fuscata, and M. cyclopis (Fig. 1), the phylogenetic hypothesis
predicts tolerant social relationships. Alternatively, since our study group lived
in a temple environment where food was clumped and restricted, and where
between group competition was virtually nonexistent, the socioecological hypothesis predicts despotic social relationships. Regardless of the role of phylogenetic
and ecological factors, the systematic variation hypothesis predicts that the
behavior patterns that constitute dominance style vary as a set. Thus, we predicted that levels of counter aggression would correspond to levels of reconciliation, regardless of whether those levels indicated despotic or tolerant social
relationships.
METHODS
Study Site
This study was conducted on a group of Assamese macaques living at the
Tukeswari temple in the district of Goalpara in the state of Assam, India. The
group lived on the temple grounds and on the steep, boulder-strewn hill behind
the temple. The hill was sparsely forested and surrounded by farmland. The
main temple was at the base of the hill and a second, smaller temple was at the
top of the hill, 110 m above the temple grounds. The monkeys raided nearby rice
fields and stole food from shops and houses. Local priests fed the monkeys daily
at each temple site, and the monkeys received food from worshipers as well.
Feeding was intense and competitive at the temple sites. Sporadic offerings could
extend feeding bouts for up to an hour.
Subjects
The group consisted of 64 animals, all well habituated and individually recognizable. No births or deaths occurred during the study period. Fourteen females and 14 males were judged to be over 4 years of age (sexually mature).
Eight females and 5 males were estimated to be 3 years of age (pubertal), and
the remainder of the group consisted of 16 juveniles and seven yearlings. Age
218 / Cooper and Bernstein
Fig. 1. The phylogenetic tree is taken from Delson [1980]. Dominance style is indicated above species for which data are available. T = tolerant, D = despotic, I =
intermediate, and ? = a degree of uncertainty. The dominance style for Sulawesi macaques is based on M. maurus, M. nigra, and M. tonkeana. This classification differs
from Thierry [2000] in that he considered Sulawesi macaques more tolerant than all other macaques, and M. fascicularis intermediate. References: 1Abegg et al. [1996],
2
Aureli et al. [1997], 3Castles et al. [1996], 4Chaffin et al. [1995], 5Matsumura [1996], 6Matsumura [1998], 7Ogawa [1995], 8Petit et al. [1997], 9Preuschoft et al. [1998],
10
Silk [1994], 11Silk and Samuels [1984], 12Silk et al. [1981], 13Taub [1980], 14Thierry [1985], 15de Waal and Luttrell [1989], 16de Waal and Ren [1988], and 17Zhao [1996].
Counter Aggression and Reconciliation / 219
estimates were made at the start of the study and were based on size and the
eruption of canines in males. Aside from mother–infant relationships, kinship
was unknown.
Procedures
A team of three observers collected data from October 1997 to February
1998. We began data collection after establishing better than 85% agreement
in focal sampling using a pre-established ethogram. Only M.C. and I.B. collected the post-conflict (PC) samples, and M.C. collected all focal samples.
We conducted focal observations on all 28 sexually mature animals. During focal samples, we recorded the identity of the initiator and recipient, the
type of behavior, and the time when the behavior occurred. The focal sample
ethogram included affiliative behavior, sexual behavior, and agonistic behavior. Our ethogram was modeled after the behavior of stumptail macaques (M.
arctoides) [Bertrand, 1969]. We also included the lip-grin, as described for
Assamese macaques [Hill & Bernstein, 1969]. Other behavioral definitions
match those used by de Waal and Luttrell [1989] and Castles et al. [1996].
Aggressive behavior included, in order of greater intensity: open-mouth threat,
lunge, charge, chase, contact aggression, bite, and severe bite. We scored all
agonistic responses individually for third-party aggression, indicating the direction of support. Counter aggression was defined as the recipient of aggression responding with aggressive behavior of any intensity. Counter aggression
did not require that opponents use aggressive signals simultaneously, nor did
it require that the fight end in a draw. Each subject was observed for 4 hr
(approximately 24 samples of 10 min each), and the order of selection was
randomized. Focal observations were restricted to periods when the monkeys
were not receiving food from priests, worshipers, or local people. An effort
was also made to reduce human interference by not performing focal observations when the monkeys were actively engaged with people. Prior to the start
of each focal sample we recorded the identity of every animal in view and its
distance from the focal subject. Distances from the focal subject were divided
into three categories: within 5 m, between 5 and 25 m, and over 25 m.
We also recorded data on aggression ad libitum. We recorded data in the
same fashion as during the focal samples. To be sure we accurately identified
the initiator and recipient of aggression in the ad libitum data, we analyzed
only those episodes for which we were confident we observed the beginning of
the encounter. We based dominance relationships on the presence of clear
submissive behavior, such as silent bared-teeth display, avoid, and flee. When
submissive types of behavior were accompanied by counter aggression, the
episode was not used for determining dominance relationships.
We performed a 10-min PC focal sample after all agonistic episodes between sexually mature animals and between sexually mature and pubertal
animals that involved a charge or more intense aggression. The PC sample
began immediately following the last agonistic response in the conflict. If fighting started again within 2 min the PC sample was extended. We used the
same data collection protocol for PC samples as for focal samples. We collected PC samples on all dyads in polyadic fights, although the two main
opponents were also identified. The main victim was the animal initially attacked, and the main aggressor was the animal that attacked most intensively and longest. For fights among sexually mature animals, priority as focal
subject was given to the animal for which we had the least amount of data.
220 / Cooper and Bernstein
The sexually mature animal was always chosen as the focal subject in fights
with pubertal animals. We attempted to sample each subject an equal number of times as an initiator and recipient of aggression. Complete counterbalancing, however, could not be achieved because some animals were rarely the
recipients of aggression.
Although methods used to measure reconciliation differ, studies often employ a matched control (MC) sample that can be compared to the PC sample.
The ideal MC sample should resemble the corresponding PC sample in every
way, but should not occur shortly after aggression. In captivity a planned MC
sample is typically performed the following day at the same time as the corresponding PC sample, but is postponed if the subject was recently engaged
in an agonistic interaction. This procedure controls for the daily fluctuation
in group activity associated with husbandry. In field studies the appropriate
MC sample is selected from baseline data, while correcting for the availability or distance between former opponents [Aureli, 1992]. In this study, MC
samples were selected from the pool of focal samples. The appropriate focal
sample was selected by matching the distance between subjects at the start
of the focal and PC sample. In the case of a tie, the focal sample closest to the
date of the PC sample was chosen. Focal samples were not performed when
the animals received food from humans. Consequently, MC samples do not
represent bouts of intense feeding. In contrast, PC samples include fights during feeding and nonfeeding conditions. We felt the MC samples were appropriate comparisons for the PC samples in the feeding condition because the
amount of affiliative contact between former opponents during PC samples
was not significantly different in the feeding and nonfeeding conditions
(Wilcoxon: Z (18) = 1.73, P > .05; see discussion for further explanation).
Analysis
Counter aggression. In the analysis of counter aggression, we used only
aggressive encounters that involved charges or more intense forms of aggression.
The victim’s response to aggression was divided into four types: 1) submit immediately; 2) hold ground and confront the opponent, but neither submit nor respond with aggression; 3) respond with aggression and eventually submit; and
(4) respond with aggression and never submit. In category 1 the recipient of
aggression issued a bared-teeth display or squeal, and/or fled. In category 2 the
recipient of aggression oriented toward the aggressor, walked backward if the
aggressor approached, and lip-grinned. In general, category 2 included ambiguous responses that could not be scored as clearly submissive or aggressive. Categories 3 and 4 combined measured counter aggression.
We analyzed the responses to aggression as weighted means. We calculated
the percentage of responses for each subject in each category, and then calculated a mean and standard deviation (SD) for all animals. The total number of
responses in each category is shown in Table I. We used two-tailed Mann-Whitney
U-tests and Wilcoxon matched-pairs tests for statistical analysis. To partially
compensate for the large number of planned comparisons, we set the significance
level at P < .01.
Reconciliation. The occurrence of reconciliation was analyzed using the PC/
MC method as developed by de Waal and Yoshihara [1983], and the time-rule
method as developed by Aureli et al. [1989] and Aureli and van Schaik [1991].
For the PC/MC method, the minute during which former opponents initiated
affiliative contact was compared in the PC and MC samples. Each PC-MC pair
Counter Aggression and Reconciliation / 221
TABLE I. Sample Sizes for Responses to Aggression
No. of subjects
Response total
Submit
Hold ground
Aggression &
submit
Aggression &
no submit
All
All
males
M-M
F-M
All
females
M-F
F-F
41
1858
1377
205
59
19
827
485
148
33
19
658
417
127
24
18
169
68
21
9
22
1031
892
57
26
22
637
554
33
20
21
394
338
24
6
217
161
90
71
56
30
26
The four responses to aggression include: 1) submit immediately, 2) hold ground and confront opponent,
but neither submit nor respond with aggression, 3) respond with aggression and eventually submit, and
4) respond with aggression and never submit. Individual subjects were pooled and the total frequency of
each response type is given. The order of each dyad represents the initiator and recipient of aggression,
respectively. For example, F-M means a female initially attacked a male, and the male’s response is shown
in the table.
was summarized as attracted, dispersed, or neutral depending on whether
affiliative contact between former opponents occurred earlier in the PC, earlier
in the MC, or at the same time, respectively. If affiliative contact did not occur
during one of the samples, the sample was assigned the maximum value. For
each focal individual, let a be the number of attracted samples, let d be the
number of dispersed samples, and let t be the total number of samples (including
neutral samples). Then the conciliatory tendency equals (a – d)/t [Veenema et al.,
1994]. Conciliatory tendency is a measure of reconciliation that takes into account baseline levels of affiliation, and is appropriate for within- and betweenspecies comparisons. A conciliatory tendency was calculated for each focal subject,
regardless of who initiated reconciliation.
For the time-rule method we recorded the minute during which former opponents initiated the first affiliative contact in the PC and MC samples. We
compared the distribution of first affiliative contacts in the PC and MC samples
using the Kolmogorov-Smirnov test. If this test was significant we performed a
Wilcoxon matched-pairs test over the time period during which the PC and MC
distributions differed. The Wilcoxon matched-pairs test accounted for individual
variability, and ensured that the Kolmogorov-Smirnov test was not biased by
the extreme behavior of a few individuals. We used the results of the time-rule
analysis to make further comparisons. For example, the number of fights reconciled (according to the time rule) was compared for male–male and female–
female opponents.
Mann Whitney U-tests or Wilcoxon matched-pairs tests were used for statistical analysis. When sample sizes were too small for individual analysis, data
were pooled and we used the z-test approximation to the binomial. All tests were
two-tailed, and the significance level was P < .05. We had 208 PC-MC pairs when
one sample was taken per fight, and 247 PC-MC pairs when multiple samples
were included from polyadic fights. Compared to fights for which only one PCMC sample was taken (17.2%, SD = 10.9), including additional PC-MC samples
from polyadic fights (16.7%, SD = 9.9) did not significantly alter the amount of
affiliative contact between former opponents in the PC samples (Wilcoxon: Z (18)
= 0.47, P >.05). Consequently, all 247 PC-MC pairs were used for analysis. Fights
among the 41 mature and pubertal animals were distributed among 19 mature
subjects. The number of PC-MC samples per subject ranged from 8 to 21. One
aggressor–victim dyad was sampled 10 times, and these two subjects also had
222 / Cooper and Bernstein
the most PC-MC samples. The sample sizes are shown for each subdivision of
the data set in Table II.
RESULTS
Counter Aggression
We observed 1,858 aggressive encounters. The victim of aggression submitted immediately in a mean of 72.5% of encounters (SD = 23.7, n = 41) (see Table
I for the raw data). Victims held ground in a mean of 10.9% of encounters (SD =
10.9, n = 41), fought back but eventually submitted in a mean of 3.2% of encounters (SD = 3.2, n = 41), and fought back without submission in a mean of 13.4%
of encounters (SD = 17.9, n = 41). The mean percentage of counter aggression
was 16.6% (SD = 18.6, n = 41), i.e., 3.2% + 13.4%.
Sex differences. Males were the victims of 827 aggressive episodes. They
received aggression from males and females in 658 and 169 episodes, respectively. Females were the victims of 1,031 aggressive episodes, and they received
aggression from males and females in 637 and 394 episodes, respectively. Figure
2 shows sex differences in the mean percentage of the four types of responses to
aggression. Females submitted immediately in a mean of 87.5% of aggressive
encounters (SD = 8.0, n = 22), while males submitted immediately in a mean of
55.1% of aggressive encounters (SD = 24.4, n = 19) (Mann-Whitney: U (21, 18) =
23.0, P < .001). Males held ground in a mean of 17.7% of encounters (SD = 12.6,
n = 19), while females held ground in 5.0% (SD = 3.3, n = 22) (Mann-Whitney: U
(21, 18) = 75.5, P < .001). Males also fought back against their opponent without
submission in a mean of 23.1% of encounters (SD = 22.7, n = 19), while females
fought back in 5.1% (SD = 4.2, n = 22) (Mann-Whitney: U (21, 18) = 40.0, P <
.001). Overall, males showed more counter aggression (mean = 27.2%, SD = 22.2,
n = 19) than did females (mean = 7.5%, SD = 5.6, n = 22) (Mann-Whitney: U (21,
18) = 37.0, P < .001).
Figure 3 shows the responses to aggression for the four different sex-class
combinations. Fights between males were more likely than fights between females
to result in the victim holding ground and confronting its opponent, and the victim
counter-attacking its opponent and winning (confront: male mean = 18.1%, SD =
14.4, n = 19, female mean = 5.2%, SD = 5.5, n = 21; Mann Whitney: U (20, 18) =
81.0, P = .001; counter aggression: male mean = 18.2%, SD = 23.5, n = 19, female
mean = 5.5%, SD = 6.9, n = 21; Mann Whitney: U (20, 18) = 101.0, P < .01). Males,
nonetheless, showed immediate submission in a mean of 60.1% of encounters with
other males (SD = 27.0, n = 19). Males were more likely to submit when they were
the victims of male aggression (mean = 60.1%, SD = 27.0, n = 19) than the victims
of female aggression (mean = 35.6%, SD = 35.5, n = 18) (Wilcoxon: Z (17) = 2.58,
TABLE II. Reconciliation Sample Sizes
Type of PC-MC pairs
No. of subjects
No. of PC-MC pairs
Mean (SD)
Total
Feeding
Non-feeding
Male-male dyads
Female-female dyads
Male-female dyads
19
19
19
9
10
17
247
125
122
106
58
83
13.0 (4.5)
6.6 (3.0)
6.4 (2.1)
11.8 (3.5)
5.8 (2.3)
4.9 (2.1)
Two subjects did not have any fights with oppositely sexed opponents. The number of PC-MC pairs is pooled
for all subjects. The mean represents the mean number of PC-MC samples per subject.
Counter Aggression and Reconciliation / 223
Fig. 2. The mean percentage for each of the four types of responses is shown for male and female subjects (mean ± SD).
P = .01). Likewise, counter aggression occurred more often when males were attacked by females (mean = 55.5%, SD = 39.0, n = 18) than by males (mean =
21.8%, SD = 23.5, n = 19) (Wilcoxon: Z (17) = 3.10, P < .01). In contrast to males,
when females received aggression they were more likely to submit immediately
than to show the other three types of responses combined, regardless of the sex of
the opponent (aggression received from females (mean = 88.2%, SD = 11.9, n = 21):
Wilcoxon: Z (20) = 4.03, P < .001; aggression received from males (mean = 87.4%,
SD = 8.0, n = 22): Wilcoxon: Z (21) = 4.11, P < .001).
224 / Cooper and Bernstein
Fig. 3. The mean percentage for each of the four types of responses to aggression is shown for different
types of dyads (mean ± SD). The order of the dyad indicates the direction of the initial aggression; for
example, female–male means female initiates aggression against male. Thus, the response is shown for the
second member of the dyad.
Reconciliation
Demonstration of reconciliation. Former opponents were more likely to
make affiliative contact during the PC sample (16.7%, SD = 9.9) than during the
MC sample (5.8%, SD = 7.3) (Wilcoxon: Z (18) = 2.98, P < .01). The PC-MC method
indicated that the proportion of attracted PC-MC pairs (15.7%, SD = 9.8) was
greater than the proportion of dispersed PC-MC pairs (4.6%, SD = 6.1) (Wilcoxon:
Z (18) = 3.0, P < .01). The overall mean conciliatory tendency was 11.2% (SD =
12.6, n = 19).
The time-rule analysis indicated that former opponents contacted sooner after the conflict than they did during the control period, and that the maximum
difference between the PC and MC distributions occurred within the first 2 min
(Kolmogorov-Smirnov: D = .422, n = 19, P < .05). This result was also confirmed
at the individual level. Subjects contacted former opponents more often in the
Counter Aggression and Reconciliation / 225
first 2 min of the PC sample (10.1%, SD = 6.8) than in the first 2 min of the MC
sample (0.9%, SD = 2.7) (Wilcoxon: Z (18) = 3.22, P < .01). For subsequent comparisons, any fight that was followed by affiliative contact between the former
opponents in the first 2 min of the PC sample was considered reconciled. The
PC-MC method yielded very similar results on the following comparisons, but for
simplicity this is not shown.
Selective attraction. Affiliation after a conflict was highly selective. Former
opponents accounted for 20.0% (SD = 13.8) of affiliative partners in the PC
samples, while they accounted for only 5.5% (SD = 8.5) during the MC samples
(Wilcoxon: Z (18) = 2.62, P < .01). If the increased affiliation between former
opponents after a fight was the result of a general tendency for opponents to act
affiliatively, then there should have been no specific increase in affiliation between former opponents.
Initiation of reconciliation. We investigated whether recipients of aggression initiated reconciliation more often than did original aggressors, and whether
recipients of aggression did so more often than they initiated other affiliative
interactions. The analysis was limited to those fights in which the initiation of
aggression was unambiguous. Owing to the small sample size, individual data
points were pooled together. Aggressors initiated reconciliation in 33 of 44 interactions, while victims initiated reconciliation in the remaining 11 interactions (P
= .006, binomial probability). Former aggressors initiated affiliative contact during the MC sample in 11 of 14 interactions, while victims initiated affiliative
contact in the remaining three interactions (P = .029, binomial probability). Recipients of aggression initiated reconciliation less often than aggressors, and recipients of aggression did not initiate affiliative contact proportionally more often
than they did during baseline.
Severity of aggression. We analyzed the proportion of fights reconciled
according to the severity of aggression. Former opponents reconciled 12.9% of
116 fights involving a charge or chase, 11.8% of 76 fights involving manual contact aggression, and 8.5% of 47 fights involving biting. We categorized severe
biting separately, and none of these eight fights were reconciled. Thus, the severity of aggression did not affect the frequency of reconciliation.
Feeding and nonfeeding conditions. Fights that occurred when food was
offered by (or taken from) priests, worshipers, or local people were compared to
fights that occurred in other contexts, which we refer to as a nonfeeding context.
The nonfeeding context included fights that occurred while foraging on natural
foods, but these fights were considered different because of the intense and competitive situation created by provisioning. Animals reconciled 10.3% (SD = 9.0) of
their fights in the nonfeeding context, and 10.1% (SD = 11.9) in the feeding context (Wilcoxon: Z (18) = .28, P > .05). The mean percentage of fights reconciled
was not significantly different.
Sex differences. Male–male, female–female, and male–female opponents
reconciled 14.9% (SD = 6.2), 10.2% (SD = 14.6), and 5.1% of their fights (SD =
13.1) (Kruskal-Wallis: [χ2 (2, n = 19) = 9.52, P < .01]). A Mann-Whitney U-test
indicated that male–male opponents reconciled more often than did male–female
opponents. Male–female opponents rarely reconciled, but, interestingly, three of
the four fights reconciled by opposite-sexed opponents involved the alpha male.
DISCUSSION
Counter Aggression
The proportion of counter aggression in this study (16.6%) is considered low
to moderate for macaques. Although this is the only data of its kind for this
species, it suggests that Assamese macaques may have a relatively rigid domi-
226 / Cooper and Bernstein
nance hierarchy. de Waal and Luttrell [1989] found that the proportion of counter
aggression in stumptail macaques (19%) was greater than in rhesus (9%), and
interpreted this difference as evidence of relaxed dominance relationships in
stumptails. More recently, counter aggression has been found to range from 1%
of aggressive episodes in pigtail macaques (M. nemestrina) [Castles et al., 1996]
to 56% in crested black macaques (M. nigra) [Petit et al., 1997]. On the other
hand, intraspecies variation in counter aggression can be as large as the difference between stumptails and rhesus, e.g., counter aggression in Japanese
macaques ranges from 12% [Chaffin et al., 1995] to 20% [Petit et al., 1997]. This
highlights the caution necessary when making a species-wide generalization for
Assamese macaques.
Sex differences in counter aggression suggest considerable variation in dominance relationships in Assamese macaques. Males counter-attacked opponents
in 27% of their encounters, while females did so in only 8% of their encounters.
Males also held their ground in fights more often than did females, and this type
of confrontation was most common in fights among males. These male–male conflicts were characterized by the dominant animal charging the subordinate, and
the subordinate facing his opponent, backing up, and teeth chattering. The teeth
chatter was not clearly a submissive signal. At times both the advancing and
retreating males simultaneously teeth chattered. Teeth chattering was also used
to enlist support [but see Aureli et al., 1994]. The tendency for males to face
their opponent is similar to the pattern of aggression describe for stumptail
macaque males. In stumptail macaques, males are wounded in their forequarters more frequently than are females [Whitten & Smith, 1984]. In this study,
counter aggression occurred most frequently when females initiated aggression
against males. Females often received aid from the alpha or beta male, but when
they did not the male victim tended to counter attack. Dominance relationships
for females therefore seemed much more strict than for males.
Reconciliation
This group of Assamese macaques had a conciliatory tendency of 11.2%, which
is similar to the 9% in rhesus [de Waal & Ren, 1988; recalculated by Veenema et
al., 1994], 12% in non-kin in Japanese macaques [Aureli et al., 1997], and 14% in
non-kin in long-tailed macaques [Aureli et al., 1997]. This group of Assamese
macaques, although not a member of the Fascicularis group, had a conciliatory
tendency similar to species of that group. Their conciliatory tendency was far
below that of stumptail, Barbary (M. sylvanus), liontailed (M. silenus), and crested
black macaques (41% [de Waal & Ren, 1988; recalculated by Veenema et al.,
1994]; 31% non-kin [Aureli et al., 1997]; 63% [Abegg et al., 1996]; and 25% [Petit
et al., 1997], respectively). Reconciliation is a relatively good index of dominance
style [Castles et al., 1996], and the low conciliatory tendency in this group of
Assamese macaques suggests that they have a despotic dominance style. Consistent with this interpretation is the finding that the recipients of aggression initiated reconciliation less often than the initiators of aggression, a characteristic of
species with a despotic dominance style [de Waal, 1993; Castles & Whiten, 1998a].
Additional research will be necessary to determine whether the conciliatory tendency found here is characteristic of the species.
Although not statistically significant, intense bouts of feeding decreased
affiliative contact among former opponents in the PC samples. Since fights in
the feeding condition were compared to MC samples from the nonfeeding condition, we may have underestimated the level of reconciliation during feeding bouts.
Counter Aggression and Reconciliation / 227
We are confident that fights during feeding bouts were reconciled at least as
often as fights in other contexts. Castles and Whiten [1998a] found that fights
over food were reconciled less often than were fights in other contexts, although
they also found that fights over food produced the same amount of behavioral
indicators of stress in the opponents as did fights in other contexts [Castles &
Whiten, 1998b]. This is consistent with the hypothesis that fights over food damage social relationships, and that reconciliation is delayed while feeding takes
priority. We agree that fights over food damage social relationships, but suggest
that reconciliation may not always be delayed. Conditions such as the distribution of food, the proximity of foragers, and the duration of a feeding bout probably influence whether reconciliation is delayed.
Phylogenetic and Socioecological Hypotheses
The low-to-moderate level of counter aggression, and the low frequency of
reconciliation observed in this study suggest that this group of Assamese macaques
have a relatively despotic dominance style. A despotic dominance style does apply to female social relationships. Females reconciled their fights infrequently
and rarely initiated counter aggression. Insofar as the correlation in macaques
between dominance style and phylogeny is based on female social relationships,
these data on Assamese macaques weaken that correlation. A phylogenetic analysis
suggests that tolerant social relationships are the ancestral condition for
macaques, and that only recently has the Fascicularis group shifted to despotic
social relationships (Fig. 1) [Matsumura, 1999; Thierry et al., 2000]. Despotic
dominance styles, however, can develop outside the Fascicularis group. For example, a despotic dominance style in pigtail macaques does not easily fit into a
phylogenetic framework (Fig. 1). Intermediate dominance styles have been suggested to help account for patterns in species such as pigtail macaques [Thierry,
2000]. Assamese macaques may provide another example of the evolution of relatively despotic female social relationships outside of the Fascicularis group.
Our knowledge of the role of habitat in shaping dominance style is still incomplete. Data on long-tailed macaques suggest that reconciliation in wild groups
is similar to that in captive groups [Aureli, 1992; Aureli et al., 1989]. Certainly
not all captive groups of macaques have despotic social relationships. So the immediate effect of clumped resources on dominance style is limited. The long-term
effects of a temple environment, however, are unknown. We do not know when
the Tukeswari Temple was constructed, but the religious site is hundreds of years
old. The presence of Assamese and rhesus macaques in the area, and the Hindu
custom of offering food to monkeys suggest that some monkeys have been receiving food at this location for many generations. How animals that have lived commensally with humans for generations differ from their wild counterparts might
provide another means of investigating the socioecological hypothesis. At present,
we cannot be sure whether the despotic social relationships in our study group
are due to the temple habitat or are representative of the species.
Systematic Variation
The low-to-moderate proportion of counter aggression, and the low frequency
of reconciliation observed in this study are consistent with the systematic variation hypothesis. Female social relationships in particular support the systematic
variation hypothesis. Male–female social relationships, however, are not easily explained by dominance style. If affiliative and agonistic behavior covary at a dyadic
228 / Cooper and Bernstein
level, then those dyads that reconcile frequently should have high levels of counter
aggression. In Assamese macaques, when females initiated aggression against
males, males counter-attacked females, and the sexes rarely reconciled. If counter
aggression was due to social tolerance, then females were tolerant of males. Counter
aggression between males and females probably reflects a power imbalance. Sexual
dimorphism in macaques makes counter aggression against females a low-risk competitive strategy for males. In contrast, counter aggression against males would be
a high-risk strategy for females. A similar power imbalance was observed in a
group of Japanese macaques in which all seven observed episodes of counter aggression occurred when a subordinate female attacked an adult male [Chaffin et
al., 1995]. In our group, females appeared to resist the presence of adult males in
the group. Adult males remained in the group by both aggressive assertion and
high rates of grooming directed toward females [Cooper & Bernstein, 2000].
In bonnet (M. radiata), Barbary, and stumptail macaques, males frequently
affiliate and appear to have behavioral mechanisms that reduce social tension.
[Silk, 1994; Paul et al., 1996; Estrada, 1984]. Assamese macaque males also appear to have tolerant social relationships. Males in this study reconciled their
fights, and they also frequently groom and mount each other [Bernstein & Cooper, 1999; Cooper & Bernstein, 2000]. Hill [1994] suggested that low sex ratios
make affiliative relationships among males more likely. The fact that these four
species live in groups with relatively even sex ratios may, in part, relate to the
tolerant social relationships among males. In addition, the males in these species are single-mount ejaculators and may have reduced or delayed dispersal
[Caldecott, 1986; Pusey & Packer, 1987; Moore, 1992].
The despotic social relationships observed among females, and the tolerant
social relationships observed among males confuse species-wide generalizations
about dominance style. Sex differences in affiliative and aggressive behavior need
to be considered when categorizing species according to dominance style. For
example, in Barbary macaques, males tend to ignore one another in competitive
situations while females tend to compete directly for limited resources [Preuschoft
et al., 1998]. The authors thought this tolerant response to aggression by males
resulted from males attempting to avoid injury, rather than from males having
strong social bonds.
ACKNOWLEDGMENTS
This research was conducted in cooperation with the Indo-U.S. Primate
Project, principal investigator Professor S.M. Mohnot. A special thank-you goes
to Arun Srivastava, Scientist-in-Charge of the Northeast Indo-U.S. team; Prabal
Sarkar, who was working on his own dissertation on Assamese macaques at the
Tukeswari temple; and Mohibul Haque, who helped us collect the data. We are
indebted to the people of the Goalpara district, who cooperated with us in so
many ways, officially and unofficially. We are also grateful to Filippo Aureli,
Carolyn Ehardt, and three anonymous reviewers for their helpful comments on
an earlier version of the manuscript.
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