ANIMAL BEHAVIOUR, 2002, 63, 637–648
doi:10.1006/anbe.2001.1897, available online at http://www.idealibrary.com on
ARTICLES
Postconflict behaviour of wild Indian langur monkeys: avoidance of
opponents but rarely affinity
VOLKER SOMMER, ALISON DENHAM & KATHERINE LITTLE
Department of Anthropology, University College London
(Received 24 November 1999; initial acceptance 11 February 2000;
final acceptance 29 August 2001; MS. number: 6414R)
Friendly postconflict (PC) interactions between former opponents have been described for a large number
of primate species held in captivity. We investigated conflict management behaviour for wild Hanuman
langurs, Semnopithecus (Presbytis) entellus entellus, in India, using a large sample of over 6000 agonistic and
affinitive interactions recorded in one one-male/multifemale troop and three all-male bands. We
compared dyadic PC affinity with the dyadic baseline affinity during the overall observation time to
minimize biases of traditional matched-control samples. PC affinity was recorded during only 15% of all
dyads (immature male–immature male 0%, adult male–adult male 0%, adult male–immature male 5%,
adult male–adult female 0%, adult female–adult female 42%). PC affinity is probably absent amongst
males because their dominance relationships are strongly asymmetrical, leaving little room for emotional
insecurity. Dyads among females, on the other hand, reflect frequent rank changes and close kinship
which probably corresponds to higher levels of emotional uncertainty and greater need for PC affinity.
Overall, PC affinity reached only 26% of the randomly expected value. Thus, the vast majority of langur
monkey opponents avoided each other after conflicts. Avoidance as a low-cost option for group-living
animals to cope with conflicts is often not possible in captivity. This suggests that reports of high rates of
reconciliation may be at least partly artefacts of captivity.

2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.
Members of many primate species approach former
opponents shortly after a conflict and initiate sociopositive behaviours such as embracing, grooming or
huddling (see reviews in Walters & Seyfarth 1987;
Kappeler & van Schaik 1992; Silk 1998; Aureli & de Waal
2000). Such responses are believed to be part of conflict
management brought about by selective pressures
that favour cooperation. Friendly reunions may reduce
tension and anxiety, increase tolerance and decrease the
likelihood of future conflict, thus effectively serving as
‘reconciliation’ (sensu de Waal & van Roosmalen 1979).
However, a reconciliatory function cannot easily be
demonstrated and not all sociopositive postconflict interactions might reflect direct efforts to repair disharmonized relationships. Some authors therefore prefer more
descriptive terms such as ‘postconflict friendly reunion’
or ‘peaceful postconflict contact’ (see Cords 1993 and
definitions in Aureli & de Waal 2000, page 387f).
Correspondence: V. Sommer, Department of Anthropology, University
College London, Gower Street, London WC1E 6BT, U.K. (email
V.Sommer@ucl.ac.uk).
0003–3472/02/$35.00/0

Various hypotheses try to explain the occurrence of
friendly reunion. The minimum cognitive capacity
hypothesis (Gallup 1982) assumes that only certain
species are capable of displaying such behaviour but does
not address its potential adaptive value. The social evolution hypothesis assumes that conflict management is a
condition for group living and thus predicts a roughly
equal rate of reconciled conflicts for all dyads (de Waal
1986b). The dominance style hypothesis expects more
egalitarian species to reconcile more often than those
with despotic hierarchies (de Waal 1989). Other explanations expect friendly postconflict contact only for
particular dyads. The reconciled hierarchy hypothesis
predicts that dominant animals grant reconciliation to
opponents in species with formalized submissive signals
(de Waal 1986b). The good relationship hypothesis predicts that certain group members reconcile to maintain
valuable interindividual relationships (de Waal 1986a).
Finally, the dominance asymmetry hypothesis states
that postconflict reunions are more likely if the
resource-holding potential of opponents is similar,
rendering the relationship more symmetrical and thus
637
2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.
638
ANIMAL BEHAVIOUR, 63, 4
generating insecurity about who is dominant and who
subordinate (Thierry 1990).
Friendly reunion after conflict (i.e. reconciliation) has
been reported for about 30 primate species (Aureli & de
Waal 2000, page 383) and is particularly frequent for the
genera Macaca (see Matsumura 1996, and references
therein) and Pan (e.g. de Waal & van Roosmalen 1979; de
Waal 1987). However, current research suffers from various shortcomings: for example (1) the variability between
groups of the same species (cf. de Waal & Luttrell 1989;
Call et al. 1996; Castles et al. 1996) is rarely addressed; (2)
the majority of studies investigate only a small fraction of
the dyads that exist in a given group; (3) all but a handful
of reports (see Discussion) are restricted to captivity;
and (4) few studies refer to colobines (McKenna 1977;
Ren et al. 1991; Björnsdotter et al. 2000). The lack of
field studies is especially regrettable since postconflict
behaviour in the wild may differ from that in captivity
where animals cannot easily maintain their distance
from a former opponent. In addition, interspecies variability can be understood only if a wider range of
social systems is investigated, and colobines are certainly
underrepresented in this respect.
In this paper we attempt to fill this gap by presenting
the first data on wild colobines. The data were recorded in
Jodhpur, northwest India, for two types of groups of
Indian langur monkeys: a one-male–multifemale troop
and three all-male bands. The data set is one of the largest
ever used in a study on postconflict interactions and
includes several dyadic categories (male–female, female–
female, male–male). We expected postconflict contacts to
differ between these types of dyads since they reflect
varying balances of cooperation and competition. For
example, females are philopatric and closely interrelated
(facilitating high levels of cooperation) whereas males
change groups frequently and are hardly ever in the
company of related adult conspecifics (translating into
high levels of competition). Such differences may
allow us to assess the validity of some of the functional
hypotheses about friendly postconflict contacts.
METHODS
Study Site and Population
Jodhpur (240 m above sea level) is in northwest India in
the state of Rajasthan at the eastern edge of the Great
Indian Desert. The climate is dry, with maximum temperatures of up to 50C during May and June and minimum temperatures around OC during December and
January. Jodhpur receives 90% of its scanty rainfall
(annual average 360 mm) during the monsoon (July–
September). The town stands on a hilly sandstone plateau
which covers ca. 85 km2.
The plateau is inhabited by a geographically isolated
population of about 1200–1300 Hanuman langurs,
Semnopithecus (Presbytis) entellus entellus (Rajpurohit &
Sommer 1991), which has been monitored since 1967
(Mohnot 1974). All langur groups forage on the natural
vegetation, which is xerophytic open scrub, and some
groups raid crops. In addition, the majority are fed by
local people for religious reasons. Proportions of natural,
provisioned and raided food items vary considerably
between groups (Sommer & Mendoza-Granados 1994).
The reproductive units are 27–29 multifemale/one-male
troops (average size 38.5 members, range 7–93). Each
troop occupies a home range of ca. 0.5–1.3 km2. Males
emigrate from their natal troops and join one of the
12–14 all-male bands (average size 11.8 members, range
2–47). Band ranges comprise 1.5–3.5 km2 but are not well
defined, because individual males can move over areas of
more than 20 km2.
Bands invade troops in an unpredictable pattern.
Changes of the adult resident male can be rapid takeovers (occurring in days) or gradual processes (up to
several months) with temporary multimale stages and
successive short adult male tenures (interim residencies;
Sommer 1988). Residencies of single adult males in
bisexual troops range from just a few days to at least 74.0
months, with an average of 26.5 months. Stable onemale situations are typical for 94.5% of a given troop’s
history. Therefore, troops are termed ‘harems’ (Sommer &
Rajpurohit 1989; Sommer et al. 1992).
Data Collection
The present study comprises about 2000 h of observation by V.S. on one troop and three bands living under
varying ecological conditions (Table 1). All group members were known individually. Study periods lasted
between 11 and 17 months. Observations were approximately equally distributed throughout the day (0600–
1800 hours) and year. Data are presented on all group
members with the exception of infant and juvenile members of the harem troop. These individuals were still
dependent on their mothers and not yet integrated into
the dominance hierarchy.
The analysis is based on a distinction between agonistic
and affinitive interactions briefly categorized below (for
details, see e.g. Hrdy 1977; Dolhinow 1978; Sommer
1996). We collected data ad libitum (Altmann 1974)
while focal-animal sampling on other topics was carried
out simultaneously. The data sets were pooled. The
observer changed his position within the group every
30 min with rotation of the randomly selected focal
animal, thus minimizing the potential bias that particular
individuals were overrepresented in the ad libitum
sample. In a forested area, ad libitum records underreported langur interactions by 22% compared to pure
focal-animal samples (Podzuweit 1994). The bias is probably smaller in the open Jodhpur habitat. For the same
reason, it is also unlikely that affinitive acts will be
recorded less than agonistic acts which are typically more
conspicuous. While this sampling procedure does not
easily allow a context analysis it greatly increases the data
density necessary to calculate baseline rates for individual
dyads (cf. Cords 1993).
The data set includes 37 monkeys. All of them were
focal animals except two adult males who succeeded each
other as harem residents of the bisexual troop. Interactions of these two males were recorded ad libitum and
SOMMER ET AL.: POSTCONFLICT BEHAVIOUR OF LANGURS
Table 1. Details of the study groups of langur monkeys at Jodhpur and methodology
Male band
Harem troop
Kailana-I
Machiya
Canal
Chopasani
Nov 1981–Sep 1982
288
Sep 1986–Dec 1987
72
Sep 1986–Mar 1988
56
Oct 1986–Feb 1988
59
6F
2F, 1M
3F
1
2
2
3
4F, 3M
3F, 4M
26
20.4
2
1
6
1
1
1
4
10
8.8
4
3.6
10
7.0
Focal observations
Hours‡
Animals
Dyads
Mean h/dyad
Minimum h/dyad
Maximum h/dyad
660
All adult females
77
573
234
660
515
All males
45
384
79
515
397
All males
6
316
234
397
420
All males
42
207
10
420
Habitat§
Range size (ha)
Open scrub
Gardens, fields
Human habitations
Water access
75
+++
—
+, —
+++
349
+++
—
+, —
+, —
165
++
++
+
++
142
+
+++
++
+++
Diet (annual feeding time)
Provisioned food (%)
Natural food (%)
Crop raiding (%)
22.2
77.8
0.0
2.4
97.7
0.0
3.0
93.8
3.2
15.6
64.6
19.8
Observation period
Total days*
Group composition†
Adult (old)
Adult (middle-aged)
Adult (young)
Immature (subadult)
Immature (juvenile)
Immature (infant)
Total members
Mean members/month
*In bands mostly dawn-to-dusk follows.
†For age classification, see Rajpurohit et al. 1995. F=female; M=male. The harem troop’s adult male (given as 1M) was replaced once during
the study period (June 1982). Bands contained only males; not all were present throughout the study because of group transfers. Some
individuals changed age classes during the study.
‡Continuous focal-animal sampling with almost equal diurnal and annual distribution. Additional scan and ad libitum sampling was carried out
during most study periods. Focal hours=subsample of present study.
§+ + + =much/many; + + =moderate; + =little/few, —=none.
in conjunction with focal samples of their 11 adult
females.
Agonistic acts (roughly in order of increasing intensity;
cf. Borries et al. 1991) were as follows.
(1) Being avoided: A moves towards B; B anticipates A’s
approach and moves away.
(2) Displace (‘A causes B to leave’): A and B are close to
each other or A approaches B. The individuals will sometimes have aggressive acoustic, visual or tactile contact
(see categories below). B moves away. A occupies position
or resource previously controlled by B.
(3) Vocalize at: A directs grunts, guttural vocalization
or teeth grinding (canines or molars) towards B.
(4) Threat: A bares canines towards B, often while
vocalizing (face threat); A raises hand(s) towards B (hand
threat); A jumps towards B (lunge threat).
(5) Fence: A prevents B from approaching further or
acquiring a resource, typically through briefly raising
both arms and threatening A.
(6) Hit or kick: A hits or kicks B, typically while A is
stationary.
(7) Pull or push ear or fur: A pulls/pushes ear(s)/fur of B
with one or both hands.
(8) Jump at: A jumps into B’s flank or on to B’s back,
often quadrupedally, typically while B moves quickly.
(9) Chase: A runs after B who flees.
(10) Bite: in females, virtually always ‘mock biting’;
males sometimes draw blood.
Affinitive acts (roughly in order of increasing intensity;
cf. Borries et al. 1994) were as follows.
(1) Grunt-and-grin: Mild vocalization accompanied by
bared-teeth display.
(2) Pat jaw: A strokes B’s jaw or pulls hair around B’s
face.
(3) Pull head: A pulls B’s head towards A.
(4) Kiss: A muzzles B’s head, often the jaw and lip
region.
(5) Embrace: A puts arms around neck or back of B who
will often reciprocate. One or several of the preceding categories could initiate an embrace or be associated with it.
(6) Move in circle: two animals describe a circle while
embracing each other.
639
640
ANIMAL BEHAVIOUR, 63, 4
(7) Invite allogrooming: A presents body parts to B,
typically flank or back or belly while raising arm(s).
(8) Allogrooming: coordinated movement through a
groupmate’s fur with one or both hands or mouth.
Particles may be removed in the process.
Agonistic female–female encounters are short events of
usually not more than a few seconds. Male–male conflicts
can be prolonged and may result in wounding (e.g.
Dolhinow 1972; Hrdy 1977). Affinitive embrace interactions do not exceed a few seconds but most allogrooming is considerably longer (among adult troop females:
5.9–68 min, N=1194; among male band members: 1.9–
23 min, N=2005; Sommer 1996).
For the purpose of this study, we considered all agonistic and affinitive acts to be events and not states. The
analysis is thus based on frequencies of behaviours.
Combinations of consecutive agonistic acts (e.g. pull fur+
hit; bite+chase) and affinitive acts (e.g. pat jaw+embrace;
invite allogrooming+allogrooming) within the same
minute were counted as only a single event. Continuous
interactions, mostly allogrooming, that span several minutes were counted as a single event; an interruption had
to last for at least 30 s before an interaction qualified as a
new event. Transforming grooming states into grooming
events is justified because grooming duration and grooming frequency are highly correlated in Jodhpur langurs
(rs =0.964, Borries et al. 1994). Polyadic conflicts are rare
in langurs and almost absent amongst females (cf. Borries
et al. 1991; Borries 1994); mutual grooming (A grooms B
while B grooms A; rare) and polyadic grooming (e.g. A
and B groom C; not uncommon) were broken down into
dyads.
Some related types of interaction were excluded. (1)
Sexual harassment: copulations of the harem holder were
frequently disturbed by one or several females (Sommer
1989). The male responded with threats or chases. Since
these resembled ‘mock attacks’ and were often polyadic,
they were excluded from the analysis. (2) Infanticide: one
of the two harem holders was infanticidal, resulting in
various aggressive attacks and joint defence by females
(Sommer 1987). Infanticidal attacks in conjunction with
the replacement of harem residents can be expected
only every 2.2 years and thus represent a particular type
of conflict outside the focus of the present study. (3)
Mounting: same-sex dorsoventral contacts resembling a
heterosexual copulation were excluded because they represent an ambiguous mixture of agonistic and affinitive
patterns (Srivastava et al. 1991). (4) Huddling: this behaviour, although common amongst many Old World primates, is very rarely seen in the Jodhpur langurs. It was
not observed during the study period (apart from females
who held immatures and huddled over them). (5)
Proximity: close spatial contact is commonly seen but
much of it seemed to be caused by the need to share
shady or comfortable spots rather than being a reflection
of affiliation. Several other studies explicitly excluded
decreased interindividual distances because of such an
ambiguous motivational basis (cf. Kappeler & van Schaik
1992). The exclusion of proximity is also the reason that
we avoid the broader term ‘affiliation’ in favour of the
more specific ‘affinity’.
Data Analysis
The ways in which postconflict contact is measured
alter the results of an analysis (see review in Kappeler &
van Schaik 1992). Many previous studies compared
behaviour during postconflict observations (PC) with that
during matched-control observations (MC). Suitable MCs
should correspond closely with characteristics of the PC.
MCs are often carried out the following day at the same
time and for the same length of time as the corresponding
PC. The PC/MC method has various disadvantages. (1) It
is basically designed for captivity. (2) It is questionable if
MCs can ever reproduce all conditions of the corresponding PC, for example, with respect to proximity of
opponents after a conflict has occurred. In the field, it is
close to impossible to define MCs that sufficiently match
the environmental and social context of PCs, such as
subgroup composition, spatial distribution of group
members, visibility, food availability and intake, temperature and external disturbances including predation risk.
These variations affect how likely it is that an affinitive
interaction between certain individuals will occur during
the MC, devaluating PC–MC comparisons considerably.
(2) The concentration on specific PC/MC pairs will
typically result in a rather sketchy documentation of
the overall dyadic pattern of interaction and often
yields dyadic samples of less than 10. (3) The period
following a conflict is likely to be influenced by its
outcome, for example whether the opponents reconcile,
and is thus not an appropriate ‘neutral’ comparison (Silk
1997).
Therefore, we did not analyse specific MC samples.
Instead, we calculated interaction rates for individual
dyads, and compared the (observed) rates of dyadic PC
affinity during a given time window after the conflict to
the (expected) rates of dyadic baseline affinity during the
overall observation time, a variation of the ‘rate method’
(de Waal 1987; Judge 1997) and the ‘time rule method’
(Aureli et al. 1989).
We recorded PC affinity immediately after an aggressive interaction. Consecutive affinitive events (e.g. pat
jaw plus embrace) within the same PC minute were
counted only once. Continuous affinity that spanned
several minutes was counted as a single event unless the
interaction was interrupted for more than 30 s. In reality,
interruptions of PC affinity were almost nonexistent. The
PC period was defined as being 3 min long since other
studies have mostly found that friendly reunions occur
immediately after the conflict (Veneema et al. 1987). The
likelihood of recording affinitive PC interactions in standard PC–MC studies decreases with longer PC periods
because of increased background noise caused by affiliation during the baseline situations (Veneema et al. 1994).
Our own method is not prone to such bias since all
recorded affinitive events are analysed anyway. As an
additional control, we calculated affinity during a 15-min
PC window to minimize the likelihood of false negatives.
We tested whether observed PC affinity was above
expected baseline levels of affinity. Baseline levels were
defined as affinitive acts/h of observation time while two
animals had the opportunity for dyadic interaction, that
SOMMER ET AL.: POSTCONFLICT BEHAVIOUR OF LANGURS
is, were members of the same group. This procedure
controls for monkeys that died, disappeared, immigrated,
emigrated or were temporarily absent from the group.
The latter refers to males only, as bands regularly split in
a fusion–fission pattern. Such subunits may lose visual
and acoustic contact with each other. The subunits will
often merge again during the day, but males may also
leave particular bands for several days or weeks (for
histories of study groups, see Sommer et al. 1992;
Rajpurohit et al. 1995). Male bands as well as harem
troops were otherwise very cohesive.
The following is an example of the calculation of rates
of dyadic PC affinity and dyadic baseline affinity. Adult
females 12 and 11 were permanent members of troop
Kailana-I during the 660 h of observation in that group
(cf. Table 1). During this period, 24 agonistic and 61
affinitive interactions were recorded for this dyad which
translates into an expected baseline rate of PC affinity of
0.11/h (61 affinitive interactions1.2 h/660 h). Two
affinitive interactions occurred within 3 min of an agonistic interaction, thus counting as PC affinity. PC observation time was 1.2 h (24 events3 min=72 min). This
translates into an observed rate of PC affinity of 1.67/h
which is well above the baseline.
There is no statistical method to test whether observed
and expected PC affinity differ significantly since pairs
had at best a few affinitive PC interactions (see Results).
Other authors also refrain from tests of significance even
if they analyse dyadic interactions via the PC–MC
method. For example, these count as ‘attracted pairs’ (i.e.
reconciled dyads) where PC affinity ‘occurred earlier in
the PC than in the MC observations’ (Call et al. 1999:
166). ‘Earlier’ is as descriptive as our use of ‘above or
below expectation’. Both approaches reflect difficulties
with small sample sizes which primatological research
will often face.
We refrain from calling affinitive PC interactions above
baseline levels ‘reconciliations’ because we do not know
enough about the motivational state of the former
opponents. Nevertheless, one could argue that, from a
heuristic point of view, PC affinity above baseline levels
could serve as an operational definition (cf. Cords 1993)
of reconciliation.
Our baseline method requires two additional steps. (1)
Affinitive acts during the first 3 min at the beginning of
each observation block were discarded because they
might represent a PC affinity that followed an agonistic
act that took place just before observations began.
Agonistic acts during the last 2 min of a given observation
block were also discarded since they might be followed by
affinitive PC interactions just after the observation ended.
(2) Baseline affinity might be inflated against PC affinity
if aggression occurs at times with lower overall affiliation.
Theoretically, aggression could be more common
during travel or feeding whereas affinity could be more
common during resting. However, this was not the case
since the hourly distribution of agonistic and affinitive
events covaried and did not differ significantly
(Kolmogorov–Smirnov test: D=0.065, N=13, NS).
Nevertheless, our method is not without biases. Unlike
‘traditional’ MC samples, we did not try to select situ-
ations similar to the PC, for example with respect to close
spatial distance of two animals. The procedure will
therefore bias against rates of affinitive baseline interactions (perhaps even more than an MC sample).
However, a reverse bias is introduced by the ad libitum
sampling since sometimes either the agonistic or the
affinitive interaction in the context of a conflict will go
unrecorded. This lack of records will bias against rates of
PC affinity, thus reducing the first error.
On the other hand, our method enables us to sample
many more PC situations than traditional studies,
whether or not one wants to conduct additional baseline
calculations. The combination of ad libitum with focalanimal sampling ensures a data density that allows the
reconstruction of solid sociometric matrices which provide background information about dominance ranks,
grooming networks and long-term dynamics of social
relationships (e.g. Borries et al. 1991, 1994). Furthermore,
the method can be used a posteriori and might facilitate
analysis of field data for other species, which are urgently
needed.
RESULTS
We identified 1365 agonistic events and 4862 affinitive
events in the four monkey groups (Fig. 1). However, a
mere 43 affinitive postconflict (PC) interactions were
recorded within 3 min of conflicts (Fig. 2) while a
single other affinitive interaction occurred up to 15 min
PC.
PC affinity was restricted to 25 of 170 dyads (14.7%),
representing a small fraction (26.1%) of the randomly
expected interactions (calculation: 3 min following each
of 1365 agonistic events amount to 68.3 h, which equal
3.4% of total observations; in this time, 3.4% of all 4862
affinitive events should have occurred, i.e. 165). No PC
affinity was recorded in band Canal and only single
episodes in bands Machiya (1.7% of potential dyads) and
Chopasani (1.2% of potential dyads). In the harem troop,
41 interactions were recorded in 23 of 76 dyads (30.3% of
potential dyads), with 6 of 23 dyads being reciprocal. The
number of affinitive PC events was either one (12 dyads),
two (10 dyads), three (one dyad) or four (two dyads). PC
events exceeded the expected dyadic rates in all recorded
instances.
Thus, 120 of 145 dyads (82.8%) had agonistic interactions but no PC affinity. The vast majority of former
opponents not only failed to establish peaceful PC contacts but also avoided affinity with each other after
conflicts.
Rates of interactions broken down for sex and age
(AF=adult female, AM=adult male, IM=immature male)
differed markedly (Fig. 3a). AM–AM dyads had the most
frequent agonistic and affinitive contact. All other age-sex
classes had much lower overall rates but affinity was 4–9
times higher than agonism amongst AM–AF, AF–AF and
IM–IM dyads. Percentages of dyads with agonistic/
affinitive interactions were as follows: AM–AF (22 dyads)
81.8/95.4%; AF–AF (55 dyads) 100.0/100.0%; AM–AM (17
dyads) 88.2/100.0%; AM–IM (50 dyads) 76.0/86.0%;
IM–IM (26 dyads) 73.0/100.0%.
641
ANIMAL BEHAVIOUR, 63, 4
(a)
Harem troop Kailana-1
Recipient
Agonism
Actor
Age
Rank
Female
F12
F11
F4
F7
F1
F13
F2
F8
F3
F6
F9
M20
M43
Y
1.3
F12
0.2
0.6
0.3
0.5
0.2
Y
2.3
F11
3.5
0.8
0.5
0.3
0.3
0.3
0.2
0.3
0.3
0.6
1.3
0.4
1.3
O
4.0
F4
0.6
2.0
0.9
0.2
0.6
0.2
0.3
0.2
0.2
0.4
M
4.0
F7
1.1
1.4
0.8
O
5.0
F1
1.2
2.4
0.2
0.3
0.2
0.2
Y
5.3
F13
0.5
2.1
0.5
0.5
0.6
O
7.0
F2
3.3
2.4
2.1
0.8
2.1
1.1
0.8
0.2
0.6
0.2
0.2
0.6
0.4
0.5
0.4
0.4
O
7.0
F8
0.8
0.8
0.9
0.6
0.6
1.5
0.3
0.2
0.6
0.8
0.2
0.2
0.4
0.4
0.2
0.9
O
97
F3
0.9
0.8
0.9
1.5
1.8
1.2
1.2
1.4
0.3
0.6
0.2
0.4
O
10.0
F6
1.2
2.9
1.4
2.0
1.5
1.5
2.6
2.6
2.1
0.5
0.6
M
A
10.3
F9 M20
0.5
2.7
0.8 0.2
1.7 0.4
0.8 0.6
0.9
1.1 0.2
2.4 1.9
1.1
1.7
A
M43
2.0
1.0
10.0
1.0
0.6
Affinity
644 Events
Female
F12
F11
F4
F7
F1
F13
F2
F8
F3
F6
F9
M20
M43
F12
Female
F12
F11
F4
F7
F1
F13
F2
F8
F3
F6
F9
M20
M43
F12
3.6
9.1
5.6
4.2
6.5
1.8
2.9
5.0
4.8
2.7
F11
5.6
7.9
6.7
8.5
5.0
1.7
2.6
2.9
1.1
1.5
F4
10.5
1.8
3.5
2.4
3.6
1.1
1.7
1.4
1.2
2.1
F7
7.9
5.8
6.2
3.9
3.6
3.3
3.5
3.3
2.0
1.4
F1
6.5
4.7
2.4
4.7
5.2
0.6
2.0
1.5
1.1
0.5
F13
12.9
3.6
6.1
3.2
3.3
F2
3.8
1.1
3.0
3.5
0.9
5.6
0.9
2.6
2.1
3.6
5.3
7.6
2.6
0.6
4.8
0.2
F8
3.3
2.0
2.4
3.2
0.8
3.0
3.3
1.2
1.8
2.6
0.2
0.4
F3
8.9
2.0
2.4
3.5
2.0
3.2
2.3
2.4
0.6
1.7
F6
7.1
0.6
2.4
2.4
1.1
4.7
1.1
2.3
2.0
0.6
0.2
F9 M20
9.7 1.0
1.2 0.2
4.8 1.7
3.2 0.2
0.6 0.8
10.0 3.6
2.4 0.8
4.2 2.1
2.3 0.8
0.2 3.1
1.5
M43
0.4
3.4
4.3
6.4
14.1
3.4
9.8
6.4
13.3
0.9
1.3
PC affinity
2747 Events
0.3
0.3
F11
0.3
0.2
F4
0.3
F7
F1
F13
F2
0.2
0.3
0.3
F8
0.2
F3
F6
0.2
M43
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.2
0.2
0.2
0.5
0.2
0.2
0.2
0.2
0.3
41 Events
(b)
Male band Machiya
Actor
Agonism
F9 M20
0.3
0.2
0.3
Age
A Y/A
S/Y
Rank
1.0
1.1
2.3
Male M86 M87 M89
M86
6.4
M87
4.4
0.0
M89 12.7
M88
3.8
1.0
M4.6
0.4
M90
0.2
M91
0.2
M93
M92
0.2
M94
0.0
Male band Chopasani
Recipient
Y J2/S
2.6
3.9
M88 M4.6
2.5
5.7
2.6
0.8
7.6
3.9
0.2
J2/S
5.1
M90
1.3
0.7
2.7
0.7
0.5
J1/2 J1/2
5.6
6.6
M91 M93
1.3
1.3
3.5
3.5
1.6
0.8
1.4
1.6
1.4
0.5
1.2
0.0
0.8
0.8
1.4
0.4
0.2
Male band Canal
Recipient
0.2
J1/2 J1/2
7.6
9.1
M92 M94
2.0
3.9
1.9
2.5
2.7
1.2
0.6
1.5
1.5
0.5
1.5
0.7
0.5
0.2
Affinity
388 Events
Male M86 M87 M89 M88 M4.6 M90 M91 M93 M92 M94
3.8
M86
3.8
2.5
1.3
0.0
M87 20.3
8.3
5.5 1.1
0.2
0.4
19.2 1.0
0.2
0.2
2.3
0.5
M89 10.2 12.3
M88 19.1
8.1 20.2
0.4
0.2 0.2
5.1
M4.6
1.3
2.3
1.2
0.5
1.0
1.2 0.8
2.4
M90
0.2
0.7 0.5
0.2
0.2 1.0
0.2
M91
1.3
0.4
0.6
1.0 0.8
4.9 2.5
4.4
M93
3.8
1.8
3.9
0.6 0.8
1.5
7.4
1.7 31.1
6.4
M92
0.7
0.4
0.8 0.6
1.2
2.3
1.2
2.4
M94
7.6
0.7
1.5
0.2 3.2
1.7
6.6 31.8 2.7
PC affinity
642
Male M86 M87 M89 M88 M4.6 M90 M91 M93 M92 M94
M86
M87
0.2
M89
M88
M4.6
M90
M91
M93
M92
M94
1051 Events
1 Event
Age
A
O
O A/O A/O J2/S
Rank
1.0
1.3
1.8
3.0
3.1
3.8
Male M76 M49 M10 M125 M204 M205
M76
19.4
1.7
M49
10.7 113.0 1.5
0.5
8.1
M10
2.5 0.2
M125
102.7
41.1
M204
1.0
M205 1.0
2.0
0.5
M208 0.5
M209 1.0
0.8 0.3
0.8
M207
M206
5.6
1.0
Recipient
J2/S
S J2/S
J2
4.4
5.4
6.5
6.8
M208 M209 M207 M206
1.9
5.3
2.1
1.4
5.6
1.2
1.2
1.4
0.5
Age
Y/A Y/A
S/Y
J2
Rank
1.4 1.6
3.0
4.0
Male M240 M120 M121 M250
9.6
5.5
1.3
M240
M120 6.3
1.5
3.8
M121 0.3
3.4
1.3
M250 1.3
125 Events
2.6
0.9
0.6
208 Events
Male M76 M49 M10 M125 M204 M205 M208 M209 M207 M206
M76
0.5 16.6
0.5
0.5
0.5
1.0
M49
1.0
1.5
2.5
1.5
1.0
1.4
3.6 6.0
1.7
M10
M125 13.3 10.3
10.3
5.7
M204
5.6
4.6
0.5
0.5
M205 3.9
13.1
1.4
2.0
5.7
4.6
9.7
6.9
M208 2.4
0.2
1.4
0.5 2.9
6.6
2.0
2.6
M209 1.5
0.3
3.7
5.8
2.4
3.2
M207
5.8
2.5
8.6
2.0
3.2
4.6
M206 1.5
2.0
6.0 10.0
3.1 8.6
3.8
5.8
4.6
Male M240 M120 M121 M250
21.4 12.1 1.3
M240
M120 19.9
5.5
M121 29.0 15.9
5.5
3.0 23.0
M250 5.5
502 Events
562 Events
Male M76 M49 M10 M125 M204 M205 M208 M209 M207 M206
M76
M49
M10
M125
M204
M205
M208
M209
M207
M206
0.5
1 Event
Male M240 M120 M121 M250
M240
M120
M121
M250
0 Events
Nonexisting
dyad
Figure 1. Agonism, affinity and postconflict affinity in (a) a harem troop and (b) three male bands. Female age classes: Y=young, M=middle
aged, O=old; male age classes: J1=Juvenile-1, J2=Juvenile-2, S=subadult, Y=young adult, A=prime adult, O=old (see Rajpurohit et al. 1995
for definitions of age classes). Individuals are arranged in descending dominance rank from left to right and from top to bottom (cf. Borries
et al. 1991). Cells are standardized as dyadic events/100 h.
SOMMER ET AL.: POSTCONFLICT BEHAVIOUR OF LANGURS
Table 2. Behavioural categories and contexts of agonistic and
affinitive baseline and postconflict interactions
PC affinity/100 h
5
4
Harem troop Kailana-I
(41 events)
3
Male band Canal
(0 events)
2
Male band Machiya
(1 event)
1
Male band Chopasani
(1 event)
0
2
1
3
4
5 6 7 8 9 10 11 12 13 14 15
Minute postconflict
(a)
SD 0.71
0.4
Agonism
Affinity
877
0.3
279
885
Mean dyadic events/h
0.2
2518
0.1
229
63
0
0.5
0.4
0.3
315 353
581
127
AM-AF
AF-AF
AM-AM
AM-IM
IM-IM
(22 dyads) (55 dyads) (17 dyads) (50 dyads) (26 dyads)
(b)
1.31
SD
3.35
Expected PC affinity
Observed PC affinity
41
0.2
0.1
0
Conflict context (baseline=561
events)*
Natural food
Provisioned food
Position, shade
Allogroom
Other/unknown
25.3
24.4
23.3
6.2
20.7
19.0
28.5
16.6
16.6
19.0
Agonism (baseline=1365 events)
Displace
Hit/kick
Pull/push
Chase
Teeth grind
Other
69.5
13.3
5.2
5.6
4.3
2.3
62.8
20.9
11.6
2.3
0.0
2.3
Affinity (baseline=4862 events)
Allogroom
Embrace
Other
94.2
5.6
0.2
48.8
51.1
0.0
Category
Figure 2. Postconflict affinity within a 15-min window in four langur
study groups.
0.5
Baseline
(%)
Postconflict
sample
(% of 43
cases)
2
AM-AF
AF-AF
AM-AM
AM-IM
IM-IM
(18 dyads) (55 dyads) (15 dyads) (38 dyads) (19 dyads)
Figure 3. Dyadic events/h among four langur age–sex class permutations. Means are given +SD. AF=adult female; AM=adult male;
IM=immature male. Numbers above bars indicate total events. (a)
Agonism and affinity. (b) Expected and observed affinitive events
within 3 min postconflict (PC).
We used the frequency of dyadic conflict to calculate
expected and observed rates of PC affinity (Fig. 3b). There
was no PC affinity in AM–AF, AM–AM and IM–IM dyads
despite some of the highest expected rates. Observed rates
for AM–IM dyads were 6.0 times higher than expected
and those for AF–AF dyads 39.2 times.
We compared the pattern of PC interactions with
baseline expectations (Table 2). (1) The contexts of
baseline conflicts and conflicts followed by PC affinity
were similar and included disputes over food, position
and grooming partners. (2) PC affinity was more
easily triggered by conflicts that involved physical contact (hit/kick; push/pull) than by nonphysical displacements. (3) Opponents expressed PC affinity more often
than expected via embracing, whereas grooming was
underrepresented.
PC affinity was more often initiated by the loser
of a conflict (58.5%) than by the winner (41.5%).
All categories were observed in all study groups.
*Harem troop Kailana-I.
Subordinates who directed PC affinity to the winner used
embracing more often than allogrooming (58.3 versus
42.7%; N=24). Dominants who directed PC affinity to the
loser used embracing less often than grooming (33.3
versus 66.6%; N=18).
Conflicts related to sexual harassment of copulations
and infanticidal attacks were excluded from the quantitative sample. In any case, PC affinity was not observed
between opponents in such instances.
We tested the possibility that specific agonistic interactions were not followed by PC affinity but that dyads
maintained some general reconciliatory balance over a
longer period. Therefore, we compared dyadic agonistic
and affinitive frequencies to see if pairs with more conflict also had more affinity (Fig. 4). However, no such
correlation was found in any study group (harem troop
Kailana-I, AF–AF dyads only: rS = 0.30, N=55, P=0.025;
male band Machiya: rS = +0.08, N=45, P=0.587; male
band Canal: rS = +0.43, N=6, P=0.399; male band
Chopasani: rS = 0.03, N=42, P=0.861).
Finally, we tried to identify predictors for dyads that
showed PC affinity. Dominance rank could be relevant
because animals that are closer in rank may have stronger
relationships than those further apart. The two incidences
of PC affinity amongst males do not lend themselves to
such analysis but for females, no correlation existed between PC affinity and dominance rank distance (rS =
0.011, N=55, NS; data on rank from Borries et al. 1991).
However, female relationships could overall be characterized as strong, as indicated by the positive ratio of
baseline affinity to agonism (cf. Fig. 3a). On average,
seven affinitive dyadic interactions occurred before one
643
ANIMAL BEHAVIOUR, 63, 4
10
0.30
(a)
0.20
0.10
0.00
0.40
0.30
0.02
0.04
0.06
0.08
0.63
0.20
0.19
0.10
0.02
0.04
0.06
0.16
(c)
0.20
0.10
0.00
0.02
0.04
0.06
0.08
0.40
0.30
(d)
0.20
2.10
0.10
0.40
0.20
0.00
6
4
2
0.02
0.04
0.06
Dyadic agonism/h
5
10
15
20
25
Ratio affinity/agonism per dyad
30
Figure 5. Postconflict affinity among adult langur females as a
function of the baseline ratio of affinity and agonism. x/C: Dyad
with/without postconflict affinity.
0.08
0.40
0.30
8
0
(b)
0.00
Observed – expected
PC affinity/h
0.40
Dyadic affinity/h
644
0.08
Figure 4. Affinity as a function of agonistic interactions in four langur
study groups. (a) Harem troop Kailana-I; (b) male band Machiya;
(c) male band Canal; (d) male band Chopasani. ◆, x/ , e, C:
Dyad with/without postconflict affinity; : female–male dyad; ◆, e:
female–female dyad; x, C: male–male dyad.
agonistic act was recorded and not a single AF–AF dyad
had more agonistic than affinitive events. The ratio was
higher for dyads without PC affinity (XSD=8.68.0,
N=32) than for dyads with PC affinity (4.23.5, N=23;
Mann–Whitney U test: Z=1.80, P<0.05, one-tailed; Fig.
5). This indicates that females with relatively weaker
sociopositive relationships were more likely to initiate PC
affinity.
DISCUSSION
In this first analysis of postconflict (PC) interactions in
wild colobines, we found rates of PC affinity well below
baseline in all four study groups of Hanuman langurs.
Interindividual rates were also low since 82.8% of
all dyads had no PC affinity at all. What might be
responsible for the relative lack of friendly reunions of
opponents in wild langurs?
Hypotheses About Reconciliation
The minimum cognitive capacity hypothesis (Gallup
1982) would assume that colobines lack individual recog-
nition and memory to reconcile. This is unlikely given
that (1) langur social life is complex (e.g. Hrdy 1977;
Sommer 1996), (2) captive colobines show some degree of
friendly PC reunion (McKenna 1977; Ren et al. 1991;
Björnsdotter et al. 2000) and (3) the study langurs were
able to avoid affinity with each other.
Lack of PC affinity and a considerable dyadic variation
in overall affinity also does not support the social
evolution hypothesis which views reconciliation as a
prerequisite of group living (de Waal 1986b).
PC affinity in Hanuman langurs did not correlate with
rank. Therefore, support is also lacking for the reconciled
hierarchy hypothesis which suggests that dominants
grant friendly PC contacts to those who acknowledge
their superior rank (de Waal 1986b).
The dominance style hypothesis predicts that a more
relaxed style in which dominant individuals are relatively
tolerant of low-ranking conspecifics correlates with high
levels of reconciliation ( de Waal 1989; de Waal & Luttrell
1989). All langur females were affinitive with all other
adult troop females and the same is true for 95.5% of
female–male and 92.5% of male–male dyads (cf. Fig. 3). In
this sense, the langurs were very tolerant of other group
members. Hanuman langurs often live sympatrically with
rhesus monkeys, Macaca mulatta (Hrdy 1977; Sommer
1996), who are certainly more despotic in their dominance style; yet (captive) rhesus cannot be said to show
lower levels of PC affinity (de Waal & Luttrell 1989). Low
rates of friendly reunions should also be associated with
low levels of victim initiation (de Waal 1989) but more
than half of all langur PC affinity was initiated by the
victims. In this respect it should be kept in mind that
categories of ‘dominance style’, which were developed
largely for cercopithecine monkeys and chimpanzees, Pan
troglodytes (de Waal 1989), may have to be redefined to
accommodate colobines.
The good relationship hypothesis maintains that
animals reconcile particularly valuable dyads (de Waal
1986a). A ‘good relationship’ could be defined as having
high affinity and low agonism compared to other dyads
(Watts 1995). However, the langur data do not support
this hypothesis. It is true that AM–AM dyads could be
characterized as ‘bad relationships’ since they showed less
baseline affinity than agonism (mean ratio 0.9) and no
PC affinity. On the other hand, AF–AM dyads (ratio
SOMMER ET AL.: POSTCONFLICT BEHAVIOUR OF LANGURS
affinity/agonism=3.5) and IM–IM (ratio 9.0) should
count as ‘good relationships’ but neither showed PC
affinity. Only AM–IM dyads (ratio 1.5) and AF–AF dyads
(ratio 4.3) showed PC affinity. Nevertheless, those AF–AF
dyads with PC affinity did not have higher ratios of
baseline affinity/agonism (4.2) than those without (8.6;
see Fig. 5). Olive baboons, Papio anubis, reconcile more
often when they are closer in rank (Castles & Whiten
1998) and thus perhaps have a relatively strong relationship worth ‘repairing’. Again, this finding could not be
replicated for langurs. Further general support for the
hypothesis would have been generated if dyads with
higher agonistic baseline rates also had higher baseline
affinity. However, a reverse correlation was found (cf.
Fig. 4).
The dominance asymmetry hypothesis states that
frequent reconciliation corresponds with high levels of
bidirectional or undecided conflicts, that is, weak dominance asymmetries (Thierry 1990). A simple measure of
dominance asymmetry can be obtained by calculating
the proportion of dyads within a given age-sex class
permutation whose agonistic interactions did not include
reversals or rank changes (cf. Fig. 1). This produces the
following results: AM–IM 71.1%, IM–IM 63.2%, AF–AM
55.6%, AM–AM 46.7%, AF–AF 34.5%. Thus, dominance
relationships amongst females were the least asymmetrical, and did indeed display the vast majority (95.3%)
of observed PC affinity. In addition, more PC affinity
(32.5%) than expected (18.5%) occurred after contact
aggression. PC affinity after contact aggression was
restricted to female langurs, suggesting that females dispute each other’s dominance position more often than
males. This should correspond with higher levels of
emotional uncertainty (Aureli & van Schaik 1991) and a
relatively greater need for PC affinity (cf. Cords & Aureli
1993). Our data thus lend general support to this hypothesis although the lack of a correlation between PC
affinity and close dominance rank remains somewhat
contradictory.
Context Analysis
Embracing was greatly overrepresented as a means to
initiate PC affinity whereas allogrooming was underrepresented (cf. Table 2). The preference for brief exploratory touches instead of extended body contact probably
reflects the tension that exists between opponents shortly
after a conflict. Nevertheless, subordinates seemed to be
more insecure after a conflict than dominants. This is
reflected in the finding that ‘appeasements’ from losers to
winners included a greater proportion of embracings than
‘reassurances’ directed from winners to losers.
Our study could not replicate the finding for some wild
primates that PC affinity was greatly reduced after conflicts over food (Aureli 1992; Matsumara 1996; Castles &
Whiten 1998) which is considered to be a heavily contested resource. Competition over food should be less
intense in colobines than in cercopithecines or chimpanzees since colobine diets contain more scattered leaves of
low calorific value. In the study langurs, displacements
over natural food were twice as frequent as expected and
displacements over provisioned food four times (Borries
et al. 1991). This indicates that langurs, too, compete for
food, and even more so if a desired resource is clumped,
such as fruits, vegetables or wheat cakes which local
people distribute. Nevertheless, PC affinity after conflicts
over food was similar to expected levels (cf. Table 2).
Some studies restrict PC analysis to aggression that
includes physical contact considering that only severe
conflicts might trigger the need to reconcile. However,
exclusion of PC affinity after less severe aggression would
hardly alter the results for wild langurs. The proportion of
conflicts after which affinity was observed would merely
increase from 43/1365 (3.2%) to 15/385 (3.9%). On the
other hand, PC affinity did occur after displacements and
was only slightly less common (62.8%) than expected
(69.5%). This draws attention to the fact that observers
may sometimes be mistaken in their judgement of what
constitutes a ‘severe’ conflict. Being displaced may well
have greater emotional impact than being hit. We are far
from being able to apply such considerations to the study
of nonhuman primates.
Our study does not address third party involvement (cf.
contributions in Aureli & de Waal 2000). Nevertheless, a
preliminary analysis reveals the occurrence of PC interactions that could be labelled as ‘consolation’ (affinity
towards the loser), ‘congratulation’ (affinity towards the
winner) and ‘protectionism’ (affinity of mothers directed
towards individuals that were aggressive towards their
offspring).
Sex Differences In PC Affinity
Wild langur females showed PC affinity more often
(41.8% of dyads) than dyads involving males (1.9%).
Female relationships were also less individualistic and
asymmetrical than those of males (compare the cluster of
female dyads in Fig. 4a with the dispersed male dyads in
Fig. 4b–d). These findings could be due to sex differences
(less intense intrasexual competition amongst females)
but may also be linked to the higher degree of genetic
relatedness in troops than bands. Paternity certainty at
Jodhpur is assumed to be very high, so that infants sired
during the tenure of given harem holders are at least
paternal half-siblings (Sommer & Rajpurohit 1989; for
genetic data on one-male troops in a different population, see Borries et al. 1999). Consequently, close kinship networks develop within troops, particularly because
female transfer has not been observed. The majority of
female dyads should therefore be resilient against
upheavals conflicts could cause. Pairs with lower ratios of
baseline affinity to agonism compensated for their relatively weaker sociopositive relationships in that they were
more likely to initiate PC affinity (see Fig. 5). Females may
need to minimize the damage that strained relationships could cause since they depend heavily on their
troopmates’ cooperation to meet challenges such as
recruitment of babysitters, home range disputes with
neighbours, defence against infanticidal males or
protection against predators (Hrdy 1977; Sommer 1996).
Males, on the other hand, showed hardly any PC
affinity. This may be due to different life history
645
646
ANIMAL BEHAVIOUR, 63, 4
trajectories. Immature males leave their natal troops and
cohorts of emigrants are often comprised of close relatives. Indeed, agonism was rare amongst immature males
while levels of affinity were high (Fig. 3a), as was the case
among (related) females. Serious aggression was absent
among immature members of male bands and with it the
need for PC affinity. However, nontroop males suffer
high mortality and will frequently transfer between
groups again. As a result, (half-)brothers have little likelihood of growing up together. Therefore, at least the
highest ranks in bands are composed of nonrelated ‘individualistic’ males. They compete heavily among each
other for access to females while alliance formation and
polyadic support are rare (Sommer 1988; Rajpurohit &
Sommer 1993). Adult males had the highest average
levels of affinity of any age-sex class combination (owing
to half a dozen strong grooming relationships; see
Figs 1b, 4b–d, 5) but also by far the most frequent
conflicts (Fig. 1a). This agonism establishes clear-cut
asymmetrical dominance relationships which again carry
little insecurity. Relationships are often short lived
because males tend to leave bands frequently (Rajpurohit
et al. 1995). Thus, there is little need to mend relationships, as in unrelated mountain gorilla, Gorilla gorilla,
females (Watts 1995).
A comparison with gorillas, where females tend to seek
peaceful PC contacts with males (Watts 1995), may also
be useful to understand the absence of PC affinity in
AF–AM dyads in wild langurs. The relationship of harem
holders and females differs greatly between Hanuman
langurs and gorillas. Unlike gorilla males, langur males do
not intervene in female conflicts, do not herd females or
display towards them and rarely participate in hostile
encounters with neighbouring troops (Sommer 1996).
Thus, langur females have much less of a reason to
appease males and to seek reassurance from them. Langur
males compete with females for food, and conflicts can
also arise over infants if females perceive males as a
threat. However, langur male–female relationships are by
and large of a secure nature, with consequently little need
for PC affinity.
Conflict Modulation Through Avoidance
The 43 affinitive interactions within 3 min of PC
amongst wild langurs represent only 14.5% of the random expectation. It is difficult to decide how this
proportion compares with other studies given the
tremendous variation in methodology. Nevertheless,
these low levels of PC affinity among wild langurs seem
peculiar given that the literature stresses its ubiquity. Our
unorthodox finding is not likely to be caused by sampling
errors, given that four groups were studied in depth for
11–17 months. Rather, the findings draw attention to
differences between studies in captivity and the wild. At
first glance, the few field studies of primate PC behaviour
seem to support the generalized idea that primates
reconcile. However, limited evidence for this claim is
revealed on closer scrutiny. All studies used variations of
the problematic matched-control (MC) sampling (see
Methods), the majority were based on single groups
and some on relatively few agonistic events. A review
reveals that the majority of studies did indeed document
few or no friendly PC contacts (commonly called
‘reconciliation’ in these reports).
(1) Vervets, Cercopithecus aethiops (Cheney & Seyfarth
1989): N=299 PC observations; 2% of nonkin and 14% of
kin dyads were reconciled.
(2) Longtailed macaques, Macaca fascicularis (Aureli
1992): 156 agonistic events; 14% showed PC affinity, 1%
in the MC.
(3) Moor macaques, Macaca maurus (Matsumura
1996): 48 agonistic events; 40% were reported as
reconciled. However, no difference existed between PC
and MC affinity once corrected for the small distance of
individuals after conflicts.
(4) Chacma baboons, Papio ursinus (Cheney et al. 1995;
Silk et al. 1997): 514 PC observations; 12% of conflicts
with nonkin and 31% with kin were reconciled. However,
most reconciliation was vocal and thus nontactile.
(5) Olive baboons (Castles & Whiten 1998): of 590
opponent pairs, 85% were excluded because they constituted single observations; 16% of the remaining ca. 90
conflicts were reconciled as opposed to 2% in the MC.
(6) Mountain gorillas (Watts 1995): after 504 conflicts in two groups, no reconciliation was observed
amongst adult females, adult males or immatures. Only
adult female–adult male dyads had above-baseline
reconciliation.
The rarity or lack of friendly PC reunion in wild
primates draws attention to the possibility that conflicts
are modulated through avoidance. Our data analysis does
not reveal if the lack of PC affinity is correlated with or
caused by spatial PC avoidance, but it is hard to imagine
that opponents will maintain close PC proximity and just
forego affinitive interactions. Aureli (1992, page 335)
suggested that ‘withdrawal does not restore the disturbed
relationship with the former aggressor’. However, to
move and temporarily to stay away is probably at least as
effective in terminating the stress experienced in conflicts
(Aureli et al. 1989) as a fast PC reunion. Avoidance
circumvents the emotional insecurity that accompanies
tactile contact with a current adversary. This should be
especially uncomfortable for the loser of a conflict
although future research will perhaps reveal more subtle,
nontactile modes of friendly PC contacts such as the
vocal exchanges reported for chacma baboons (Silk et al.
1997).
The low-cost option of temporarily avoiding contact
with opponents is not easily available to captive primates,
and certainly not to the extent of field conditions. This is
also true for an early captive study of Hanuman langurs
reporting that over half of all aggressive encounters were
followed by grooming, although these figures were not
compared with baseline expectations (McKenna 1977).
Similarly, in wild longtailed macaques, the victim tended
to avoid the former aggressor when reconciliation did
not take place (Aureli 1992) and avoidance was also a
common PC strategy in mountain gorillas (Watts 1995).
One could argue that wild primates that travel in
relatively cohesive groups, such as langurs, will not
easily move away from opponents because this entails
SOMMER ET AL.: POSTCONFLICT BEHAVIOUR OF LANGURS
considerable risks such as encounters with unfamiliar
environments, predators or hostile neighbouring groups.
However, the crucial difference to a captive setting is that
subordinates can flee far and away if they want to. A
dominant attacker in pursuit must similarly shoulder
the increased risks associated with leaving the core of
the group and is likely to learn this trade-off rapidly,
consequently refraining from extended pursuit. The
space available to captive animals, on the other hand, is
finite. Subordinates are likely to learn that they cannot
easily escape from a pursuit and may therefore prefer
to approach the animal with whom they had a current conflict. The size of the enclosure matters little in
this respect which may explain why macaques show
more or less the same patterns of peaceful PC contact
under varying population densities (Judge & de Waal
1997).
Nevertheless, we do not want to imply that captive
studies of PC behaviour do not provide valuable insights;
above all, they demonstrate the behavioural flexibility of
nonhuman primates in varying environments. However,
it is likely that the majority of reports of reconciliation amongst primates are artificially inflated by the
conditions of captivity.
References
Altmann, J. 1974. Observational study of behavior: sampling
methods. Behaviour, 49, 227–267.
Aureli, F. 1992. Post-conflict behaviour among wild longtailed macaques (Macaca fascicularis). Behavioral Ecology and
Sociobiology, 31, 329–337.
Aureli, F. & van Schaik, C. P. 1991. Post-conflict behaviour in
long-tailed macaques: II. Coping with the uncertainty. Ethology,
89, 101–114.
Aureli, F. & de Waal, F. B. M. (Eds) 2000. Natural Conflict
Resolution. San Diego: California University Press.
Aureli, F., van Schaik, C. & van Hooff, J. 1989. Functional aspects
of reconciliation among captive long tailed macaques (Macaca
fascicularis). American Journal of Primatology, 19, 39–51.
Björnsdotter, M., Larsson, L. & Ljungberg, T. 2000. Post-conflict
affiliation in two captive groups of black-and-white guereza
Colobus guereza. Ethology, 106, 289–300.
Borries, C. 1994. Ecology of female social relationships: Hanuman
langurs (Presbytis entellus) and the van Schaik model. Folia
Primatologica, 61, 21–30.
Borries, C., Sommer, V. & Srivastava, A. 1991. Dominance, age,
and reproductive success in free-ranging female Hanuman langurs
(Presbytis entellus). International Journal of Primatology, 12, 231–
257.
Borries, C., Sommer, V. & Srivastava, A. 1994. Weaving a tight
social net: allogrooming in free-ranging female langurs (Presbytis
entellus). International Journal of Primatology, 15, 421–443.
Borries, C., Launhardt, K., Epplen, C., Epplen, J. T. & Winkler, P.
1999. DNA analyses support the hypothesis that infanticide is
adaptive in langur monkeys. Proceedings of the Royal Society of
London, Series B, 266, 901–904.
Call, J., Judge, P. G. & de Waal, F. B. M. 1996. Influence of kinship
and spatial density on reconciliation and grooming in rhesus
monkeys. American Journal of Primatology, 39, 35–45.
Call, J., Aureli, F. & de Waal, F. B. M. 1999. Reconciliation patterns
among stumptailed macaques: a multivariate approach. Animal
Behaviour, 58, 165–172.
Castles, D. & Whiten, A. 1998. Post-conflict behaviour of wild olive
baboons. I. Reconciliation, redirection and consolation. Ethology,
104, 126–127.
Castles, D., Aureli, F. & de Waal, F. B. M. 1996. Variation in
conciliatory tendency and relationship quality across groups of
pigtail macaques. Animal Behaviour, 52, 389–403.
Cheney, D. L. & Seyfarth, R. M. 1989. Redirected aggression and
reconciliation among vervet monkeys, Cercopithecus aethiops.
Behaviour, 110, 258–275.
Cheney, D. L., Seyfarth, R. M. & Silk, J. B. 1995. The role of grunts
in reconciling opponents and facilitating interactions among adult
female baboons. Animal Behaviour, 50, 249–257.
Cords, M. 1993. On operationally defining reconciliation. American
Journal of Primatology, 29, 255–267.
Cords, M. & Aureli, F. 1993. Patterns of reconciliation among
juvenile long-tailed macaques. In: Juvenile Primates (Ed. by M. E.
Pereira & L. A. Fairbanks), pp. 271–284. Oxford: Oxford University
Press.
Dolhinow, P. J. 1972. The North Indian langur. In: Primate Patterns
(Ed. by P. J. Dolhinow), pp. 181–238. New York: Holt, Rinehart &
Winston.
Dolhinow, P. J. 1978. A behavior repertoire for the Indian langur
monkey (Presbytis entellus). Primates, 19, 449–472.
Gallup, G. 1982. Self-awareness and the emergence of mind in
primates. American Journal of Primatology, 2, 237–248.
Hrdy, S. B. 1977. The Langurs of Abu. Female and Male Strategies
of Reproduction. Cambridge, Massachusetts: Harvard University Press.
Judge, P. 1991. Dyadic and triadic reconciliation in pigtail macaques
(Macaca nemestrina). American Journal of Primatology, 23, 225–237.
Judge, P. & de Waal, F. B. M. 1997. Rhesus monkey behaviour
under diverse population densities: coping with long-term
crowding. Animal Behaviour, 54, 643–662.
Kappeler, P. & van Schaik, C. P. 1992. Methodological and
evolutionary aspects of reconciliation among primates. Ethology,
92, 51–69.
McKenna, J. 1977. Patterns and functions of grooming
behavior among the common Indian langur monkey. Kroeber
Anthropological Society Papers, 50, 3–12.
Matsumura, S. 1996. Postconflict affiliative contacts between
former opponents among wild moor macaques (Macaca maurus).
American Journal of Primatology, 38, 211–219.
Mohnot, S. M. 1974. Ecology and behaviour of the common Indian
langur, Presbytis entellus. Ph.D. thesis, University of Jodhpur.
Podzuweit, D. 1994. Sozio-O
} k̈ologie weiblicher HanumanLanguren (Presbytis entellus), in Ramnagar, Südnepal. Ph.D. thesis,
Universität Göttingen.
Rajpurohit, L. S. & Sommer, V. 1991. Sex differences in mortality
among langurs (Presbytis entellus) of Jodhpur, Rajasthan. Folia
Primatologica, 56, 17–27.
Rajpurohit, L. S. & Sommer, V. 1993. Juvenile male emigration
from one-male troops in Hanuman langurs (Presbytis entellus): a
long-term study of intrasexual competition. In: Juvenile Primates
(Ed. by M. Pereira & L. Fairbanks), pp. 86–103. New York: Oxford
University Press.
Rajpurohit, L. S., Sommer, V. & Mohnot, S. M. 1995. Wanderers
between harems and bachelor bands: male Hanuman langurs
(Presbytis entellus) at Jodhpur in Rajasthan. Behaviour, 132, 255–
299.
Ren, R., Yan, K., Su, Y., Qi, H., Liang, B., Bao, W. & de Waal,
F. M. B. 1991. The reconciliation behavior of golden monkeys
(Rhinopithecus roxellanae roxellanae) in small breeding groups.
Primates, 32, 321–327.
Silk, J. B. 1997. The function of peaceful post-conflict contacts
among primates. Primates, 38, 265–279.
Silk, J. B. 1998. Making amends. Adaptive perspectives on conflict
remediation in monkeys, apes, and humans. Human Nature, 9,
341–368.
647
648
ANIMAL BEHAVIOUR, 63, 4
Silk, J. B., Cheney, D. L. & Seyfarth, R. M. 1997. The form and
function of post-conflict interactions between female baboons.
Animal Behaviour, 52, 259–268.
Srivastava, A., Borries, C. & Sommer, V. 1991. Homosexual
mounting in free ranging female Hanuman langurs (Presbytis
entellus). Archives of Sexual Behaviour, 20, 487–512.
Sommer, V. 1987. Infanticide among free-ranging langurs (Presbytis
entellus) at Jodhpur (Rajasthan/India). Recent observations with a
reconsideration of hypotheses. Primates, 28, 163–197.
Sommer, V. 1988. Male competition and coalitions in langurs
(Presbytis entellus) at Jodhpur, Rajasthan, India. Human Evolution,
3, 261–278.
Sommer, V. 1989. Sexual harassment in langur monkeys (Presbytis
entellus). Competition for ova, sperm, and nurture? Ethology, 80,
205–217.
Sommer, V. 1996. Heilige Egoisten: Die Soziobiologie indischer
Tempelaffen. Munich: C. H. Beck.
Sommer, V. & Mendoza-Granados, D. 1994. Play as an indicator of
habitat quality: a field study of langur monkeys (Presbytis entellus).
Ethology, 98, 1–16.
Sommer, V. & Rajpurohit, L. S. 1989. Male reproductive success
in harem troops of Hanuman langurs (Presbytis entellus).
International Journal of Primatology, 10, 293–317.
Sommer, V., Srivastava, A. & Borries, C. 1992. Cycles, sexuality,
and conception in free-ranging female langurs (Presbytis entellus).
American Journal of Primatology, 28, 1–27.
Thierry, B. 1990. Feedback loop between kinship and dominance: the macaque model. Journal of Theoretical Biology, 145,
511–521.
Veenema, H. C., Das, M. & Aureli, F. 1994. Methodological
improvements for the study of reconciliation. Behavioural
Processes, 31, 29–38.
de Waal, F. B. M. 1986a. Conflict resolution in monkeys and apes.
In: Primates: The Road to Self-sustaining Populations (Ed. by K.
Benirschke), pp. 341–350. Berlin: Springer.
de Waal, F. B. M. 1986b. The integration of dominance and social
bonding in primates. Quarterly Review of Biology, 61, 459–479.
de Waal, F. B. M. 1987. Tension regulation and nonreproductive
functions of sex in captive bonobos (Pan paniscus). National
Geographic Research, 3, 318–335.
de Waal, F. B. M. 1989. Dominance ‘style’ and primate social
organization. In: Comparative Socioecology (Ed. by V. Standen &
R. A. Foley), pp. 243–263. Oxford: Blackwell.
de Waal, F. B. M. & Luttrell, L. M. 1989. The similarity principle
underlying social bonding among female rhesus monkeys. Folia
Primatologica, 46, 215–234.
de Waal, F. B. M. & van Roosmalen, A. 1979. Reconciliation
and consolation among chimpanzees. Behavioral Ecology and
Sociobiology, 5, 55–66.
Walters, J. R. & Seyfarth, R. M. 1987. Conflict and cooperation. In:
Primate Societies (Ed. by B. B. Smuts, D. L. Cheney, R. M. Seyfarth,
R. W. Wrangham & T. T. Struhsaker), pp. 306–317. Chicago:
University of Chicago Press.
Watts, D. P. 1995. Post-conflict social events in wild mountain
gorillas (Mammalia, Hominoidea). I. Social interactions between
opponents. Ethology, 100, 139–157.