Dissertation FCT

1. 1
NEREA AMEZCUA-VALMALA
(FCT grant reference SFRH/BD/69069/2010)
PhD Dissertation title: Sociality, networking, and conflict management
strategies in hominoid primates
PhD Research project presented to the Scientific Board of ISCSP, The
University of Lisbon
(Research project present for the doctored degree in Social Sciences,
Anthropology speciality)
Supervisor: Profa. Doutora Catarina Casanova (ISCSP)
Co-supervisor: Prof. Doutor Fernando Colmenares (Universidad Complutense de Madrid,
Spain)
Instituto Superior de Ciências Sociais e Políticas da Universidade de
Lisboa
May 2017

2. 2
INDEX
1. Introduction -----------------------------------------------------------------------------------3
1.1.State of the Art. ------------------------------------------------------------------------ 3
1.2.Summary of Project and Research Goals--------------------------------------- 5
2. Methodology ----------------------------------------------------------------------------------6
2.1.Study groups and housing conditions----------------------------------------------6
2.2.Data collection---------------------------------------------------------------------------9
2.3.Chronogram----------------------------------------------------------------------------12
3. Results, discussion and final remarks-------------------------------------------------12
3.1.Study 1: Activity budgets and socio-0spatial behaviour
in captive groups of hominoids: A comparative study
of chimpanzees and gorillas--------------------------------------------------------13
3.2.Study 2: A system for recording and coding social
interactions: the case of conflict management strategies--------------------14
3.3.Study 3: Conflict management strategies in groups of
chimpanzees and gorillas: a comparative study------------------------------16
4. References-----------------------------------------------------------------------------------18

3. 3
1. INTRODUCTION
1.1 State of the Art
Living in groups is a behavioural strategy that has been selected for in a
large number of animal species, including humans and other hominoid primates
(Standen & Foley, 1989). Although sociality is a widespread phenomenon, the
specific mechanisms and processes that may give rise to and maintain the
structuring and cohesion of social groups remain poorly understood. For
example, many social groups are the outcome of several individuals exploiting
resources (food, mates, friends, allies) that are locally concentrated. In other
words, they happen to be together because they are attracted to the same
resources, but not to one another. Moreover, in many of such groups, the
individuals do not have individualised relationships with any one partner within
their groups. In large contrast, there are other species in which the individuals
live in highly cohesive societies where group members are clearly attracted to
one another, develop strong affective bonds, and establish long term
personalized partnerships, sometimes for life (De Waal & Tyack, 2009; Hinde,
1983).
The primate order, that includes humans, is made of reputedly social
species (Dunbar, 1988; Lee, 1999). However, although they tend to live in social
groups, the characteristics of their grouping units can be very variable both within
and across species. This means that the very same outcome (group life) may
arise through a variety of processes that may be activated by different
mechanisms. For example, the groups tend to contain subgroups or networks or
cliques and the individuals tend to exhibit quantitative and qualitative differences
in their social behaviour depending on whether they are interacting with their
partners versus other individuals outside their social network. In several studies
in which this issue has been subjected to scrutiny, researchers have found that
regardless of a group’s size, individuals tend to cultivate relationships with just a
few of their members, those that belong to the same network (Dunbar, 1989;
Henzi, Lycett, & Weingrill, 1997). This implies that social time is really a serious
constraint on the chances that individuals have of maintaining membership in

4. 4
large networks. It appears that individuals have a quota for social time and that
the way they deal with this constraint can be very different from one individual to
another and can also vary as a function of environmental factors. It has been
argued that networking reflects the attempts on the part of the incumbent
individuals to maximise fitness (and other more proximate functions, for example,
psychological well-being) via establishing and maintaining relationships with
valuable partners, i.e., those that may make a greater contribution to their fitness
(Arnold & Whiten, 2001, 2003; Colmenares, 2006; Cords, 1997; de Waal, 1986b,
1989, 1997; Hemelrijk, Meier, & Martin, 1999; Mitani, Merriwether, & Zhang,
2000; Mitani, Watts, Pepper, & Merriwether, 2002; Noe, de Waal, & van Hooff,
1980).
The study of social relationships and group structure has traditionally been
based on the recording and analysis of dyadic interactions. However, if sociality
is an important outcome that benefits group members, even though at varying
extents, one should expect that individuals were concerned about the interactions
between their companions. In other words, one should expect relatively high rates
of polyadic interactions in which third-parties or bystanders intervene in ongoing
agonistic and/or affiliative dyadic interactions between their fellows. For example,
individuals should exhibit aggressive, peaceful or impartial interventions when
two group members are engaged in an agonistic encounter, especially if one of
the antagonists is a friend or an ally. On the other hand, and by the same token,
individuals should be expected to express their concern when their friends are
engaged in friendly interactions with third-parties, as these interactions may
weaken their bonds and jeopardize their investments. The studies that have been
done with this perspective in mind have yielded very important insights about the
polyadic nature of the relationships that maintain group structure and have
reconciled theory and observations (Aureli & de Waal, 2000; de Waal, 2000; de
Waal & van Roosmalen, 1979).
In addition to these issues, there is the position that social life has fuelled
the evolution of intelligence and of that part of the brain that is more directly
involved in sustaining advanced socio-cognitive skills (i.e., neocortex). Thus,
under such labels as the Machiavellian hypothesis and the social brain
hypothesis, authors have looked to see how the demands of a complex social

5. 5
environment have shaped the mental abilities that socially living primates (and
other social animals) appear to display (Byrne & Whiten, 1997; Dunbar, 1998).
These abilities should surface especially in situations that are cognitively
demanding, for example, when an individual has to direct motivationally different
behavioural patterns towards several partners with whom a simultaneous
interaction is taking place, or has to keep an eye on uninvolved third parties in
order to anticipate and influence the course of their likely intervention (Boesch &
Tomasello, 1998; Castles, 2000).
1.2 Summary of Project and Research Goals
Sociality is a widespread behavioural strategy among animals. Humans
and the other primates stand out for being both very social and sociable and for
having evolved a highly developed social intellect. This research co-supervised
by scientists from Portugal and Spain, studies the mechanisms that drive sociality
in hominoid species (humans and non-human apes). We collected observational
data on several captive groups of gorillas and chimpanzees. First, we analysed
and compared the distribution of their daytime on different social and non-social
activities. Sociability was be assessed by studying social interactions and the
characteristics of several proximity measures. These measures included three
socio-spatial indices (i.e., sociality, closeness, gregariousness), and the analysis
of their social networks within two arms’ reach. Second, we developed a
recording and coding system that includes new perspectives over the treatment
and the analysis of conflicts in social groups. This system provides information
on the polyadic nature of their interactions during conflicts and on the role of
relationships with third-parties. Finally, we studied conflict management
strategies in gorillas and chimpanzees housed in all-male groups, we applied the
coding system earlier developed to analyse conflicts and assessed gorillas and
chimpanzees dominance styles.

6. 6
2. METHODOLOGY
2.1 Study groups and housing conditions
The subjects of this study were 39 adult hominoid primates, 26
chimpanzees (Pan troglodytes spp.) and 13 western lowland gorillas (Gorilla
gorilla gorilla), housed at different captive settings. I collected behavioural and
socio-spatial data on 16 male and 10 female chimpanzees from three social
groups, and on nine male and four female gorillas from two social groups (Table
1).
Three social groups of chimpanzees were studied:
1. An all-male group: Individuals were housed at La Vallée des Singes
(France); most individuals were related and they arrived together in the
park in 1998. All of them came from a pharmacological laboratory in the
Netherlands, but no research had been conducted on them. This AMG
was studied during two periods, during the first period the group consisted
of 10 eight to 13 years old adolescent and young adult chimpanzees;
during the second period one of the members had died and the group was
composed of nine young adult males. Chimpanzees had access to an
indoor facility and an outdoor island surrounded by water canals. In winter
time, both enclosures were available except when weather conditions
were harsh or when the canals’ water was frozen. In most of spring and
summer months the access to the indoor enclosure was locked. The
indoor enclosure was composed of 4 interconnected cages totalling
around 300m2
, with “ecosol” substrate and straw, both horizontal and
vertical structures and contained ropes, nets and other enrichment
materials. The island totalled 7000m2
and was provided with trees, natural
vegetation and foraging items, and was enriched with a termite mound
replica with honey inside. During the first study period chimpanzees were
studied under three different housing conditions: when the park was
closed to visitors chimpanzees were observed in the indoor enclosure

7. 7
(condition 1: indoors/non-visitors) and in the outdoors island (condition 2:
outdoors/non-visitors), when the park was open to visitors chimpanzees
were observed in the island (condition 3: outdoors/visitors). During the
second period, chimpanzees were only studied in the island and with the
presence of visitors (condition 3).
2. A multi-male/multi-female group: Individuals were housed at the Zoo-
Aquarium of Madrid (Zam). This group was composed of nine sexually
mature individuals, four adult and young adult males aged 11 to 14 years
old, one seven years old adolescent male and four adult females. The
chimpanzee exhibit consisted of an outside 469 m2
cage with some vertical
platforms, different height levels and visual barriers. The perimeter of the
cage was surrounded by walls of glass. The park was open daily and the
presence of visitors was common, animals were fed several times a day
and water was available ad libitum.
3. A one-male/multi-female group: Chimpanzees were housed at the
Jardim Zoologico de Lisboa, Portugal (Jzl). This group was composed of
12 individuals, one adult male, six adult females and their five infant
offspring, only the seven adults were subjects in the study. Data were
collected while the animals stayed at the outdoor facility.
The
chimpanzees’ exhibit was surrounded by water canals and naturalistic
stone walls totalling 1092 m2
, with vertical wooden platforms, ropes, grass
lawn ground, condemned trees and enrichment items. Water was
available ad libitum.
Two social groups of gorillas were studied:
1. An all-male group: Gorillas were housed at Loro Parque in Tenerife,
Spain. This group was composed of six males of which two were 12 year
old blackbacks and four were 19 to 24 years old silverbacks. The gorilla
exhibit consisted of an outdoor terrace with natural vegetation, wooden
structures, trunks, rocks, waterfalls and different height levels where they
could move freely. Subjects were isolated in individual dormitories for the

8. 8
two main daily meals (morning and night) and to sleep overnight. Animals
were fed three times a day and were provided with enriching feeding items.
Water was available ad libitum. Data were collected under two conditions,
during the most part of the study gorillas had access to the whole terrace
of 3500 m2
(condition 1: whole terrace or spatially non-crowded), but
during a small period, due to maintenance and improvement works of the
terrace, the access was restricted to one half of the terrace (condition 2:
half terrace or spatially crowded).
2. A one-male group: Gorillas were housed at La Vallée des Singes in
France. This group was composed of 12 individuals where only four were
fully grown up adults, the silverback alpha male and three females. The
other eight individuals were the offspring to the females and the silverback,
of which one was an adolescent female of seven years of age and two
males were blackbacks. Adult and adolescent individuals were studied:
the silverback, the three adult females, the two blackbacks and the
adolescent female. During the study period the individuals were in a 4500
m2
island with trees and natural vegetation and trunks and it was
surrounded by water canals.

9. 9
Table 1: Study groups and conditions
1. Structure: AMG: all-male group; MMG: Multi-male/multi-female group; OMG: One-male/multi-
female group. 2. Age category: based on Howell et al. (2006) for chimpanzees and on Watts
(1990) for gorillas: Sb : Silverback; Bb : Blackback; Ado: adolescent. 3. Facility: Ind: indoors
cages, is: island, out: outdoors cages, te: terrace. 4. Study sites: LSV: La Vallée des Singes, La
Vienne, France; ZAM: Zoo- Aquarium Madrid, Spain; JZL: Jardim Zoologico Lisboa, Portugal; LP:
Loro Parque, Tenerife, Spain. * In the whole terrace condition n=6, in the half terrace condition
n=5.
2.2 Data collection
I used a variety of sampling and recording methods. I relied on scan
sampling to collect data on proximity measures and activity categories; on focal-
group continuous sampling to collect baseline behavioural and social interaction
measures of individuals and dyads. Recording techniques included both
continuous and time-sampling methods.

10. 10
Via scan sampling, the frequency of the activities and socio-spatial
information of all the individuals were recorded on all study groups. These records
included information on the identity and proximity category of neighbours. Group
scan data were collected every 15 minutes or more to ensure independence
between consecutive observations, in Lvsh gorilla group, focal-scan data were
collected using a 5 minutes interval between consecutive scans.
Focal-group and group scan observations provided information about
proximity patterns and activities budgets. I collected data on various proximity
categories: contact (C), within one arm’s reach (P1), within two arms’ reach but
beyond one arm’s reach (P2), and within 3 m but beyond two arms’ reach (P3), I
collected an additional distance category for gorillas, within 5 m but beyond 4
meters (P4). Activity budgets included both solitary and social interactions and
were mutually excluding categories. Scan data provided a total of 1294 group
scan observations distributed across the 4 study groups and conditions, and 227
focal scan at the Lvsh group (see table 2: data collection).
Via group-focal sampling, social interactions and several non-social and
self-directed behaviours were recorded in the chimpanzees’ and gorillas’ AMG.
Data collection included 43 observation hours of the chimpanzee AMG and 27
hours and 30 minutes in gorillas. From the overall data collection, three periods
that were determined by the occurrence and temporality of conflicts were
distinguished: periods without conflicts (non-conflict), with conflicts (conflict) and
after conflicts (post-conflict). Behavioural information on all individuals was
collected during 15 minutes long periods at 15-s intervals as indicated by an MP3
on affinitive, agonistic, social play and self-directed behaviours (Table data
collection and study conditions).

11. 11
Table 2: Data collection and study conditions
GROUP CONDITIONS DATA COLLECTION
Group-
scans
Focal-group continuous
minutes
LVS07 C1: Indoors/non visitors
C2: outdoors/non visitors
C3: outdoors/visitors
C1: 178
C2: 85
C3: 103
C1:
2597
Non-
conflict :1559
Conflict : 549
Post-conflict :
489
LVS09 Outdoors/Visitors 192
ZAM Outdoors/Visitors 318
JZL Outdoors/Visitors 129
LP C1: Outdoors/Visitors
whole terrace
C2: Outdoors/Visitors half
terrace
C1: 227
C2: 62
C1:
1650
Non-conflict:
1044
Conflict: 324
Post-conflict:
282
Focal-
scans
LVSh Outdoors/Visitors 227

12. 12
2.3 Chronogram
Draft Proposal to
Supervisors
2009 Accepted
FCT Grant Project 2010 Submitted and accepted: FCT grant
reference SFRH/BD/69069/2010
Data collection and data
coding completed
2014 Accomplished
Data analysis completed 2015 Accomplished
Review findings with
Supervisors
2015 Accomplished
Writing PhD dissertation
chapters completed
2016 Accomplished
Final PhD manuscript draft
finished
May
2017
Accomplished
Submission of the PhD final
draft to the Scientific Board
May
2017
Ready to be submitted
Oral examination of the
PhD research dissertation
July
2017
Waiting for acceptance
3. RESULTS, DISCUSSION AND FINAL REMARKS
This dissertation comprises several chapters. Chapter 1 is a general
introduction that summarizes the major theoretical frameworks and empirical
findings relevant to the objectives addressed in the present dissertation work. It
also spells out the general objectives tackled in the study. Chapter 2 provides
some background information on the study groups and the general methodology.
Chapters 3 to 5 have a paper-format layout. Two of them (chapters 3 and 4)
address a number of empirical questions relating to group structure and conflict
management strategies, whereas the third one (chapter 5) proposes a system for
recording and coding behavioural interactions in socially living animals, especially
during agonistic conflicts. Finally, chapter 6 provides a general discussion of the
main results obtained in this research project and ends with some final remarks.
In the following, I briefly describe some of the major findings from the three
studies:

13. 13
3.1 Study 1: Activity budgets and socio-spatial behaviour in captive groups
of hominoids: A comparative study of chimpanzees and gorillas
The analysis of the activity budgets in captivity and compared to several
wild populations revealed great variability in both species. It seems that the
demography of groups had consequences on the distribution of time budgets and
that males were the most responsible for affiliative exchanges. Independently of
their grouping patterns and, in particular, of their sex-ratio, chimpanzees were
more likely to invest in social activities, were closer, more sociable, more
gregarious and their networks were more cohesive than those of gorillas.
We found out that the demographic composition of groups was likely to
impact on the type of social exchanges and proximity relationships, and also on
stress responses. Male bonding was evident in the all-male group in which social
interactions and proximity relationships were more intense than in the other two
colonies, besides a community composed only by males was found in the multi-
male group. In the all-male group individuals aggressed, affiliated and emitted
more self-directed behaviours. In the one-male group contact was reduced but
despite that stress responses were higher in the multi-male than in the one-male
group, we failed to find increased aggression in the multi-male group due to
mating competition.
It seems that in gorillas, housing several males together can be a useful
husbandry practice but that should be implemented with caution. Individuals
aggressed one another in the all-male group, whereas they did not at all in the
one-male group. Although living in one-male groups may be the optimal strategy
for gorillas, the number of males to be housed outnumber the available groups
and thus all-male groups may become an adequate housing alternative. The role
that keepers play to reduce the risk of injuries was capital in the all-male group
and in order to reduce the risk of serious fights, keepers may have to survey
aggressive exchanges, increase enrichment activities and provide areas to
reduce visual contact between individuals. In one-male groups in which there are
maturing males, special attention need be paid to changes in the relationships of

14. 14
these with the silverback and provide alternative housing for males in cases
where conflicts arise.
In general both species successfully coped with crowding reflecting the
plasticity to adjust their behaviours to changing conditions. Chimpanzees
responded similarly to crowding and to the presence of visitors, they selectively
employed alternative modes of interaction as predicted by de Waal’s coping
model. Although affiliations increased, so did aggressions too, but stress
responses did not blow up. In gorillas, and contrary to our predictions, contact
was reduced, neither aggressions nor affiliations increased which fits with a
conflict-avoidance strategy. Husbandry practices may have helped to reduce the
risk of conflicts in the gorilla all-male group. Finally, chimpanzees’ activity budgets
and proximity relationships remained more or less stable across time. Besides
some companionship preferences were the same in both periods suggesting that
in this group some pairs established friendship relationships.
3.2 Study 2: A system for recording and coding social interactions: the case
of conflict management strategies
When one regards the evolution of the research on primate social systems,
several levels of complexity can be easily recognized. Initial attempts to
understand the structure of social groups focused on dyadic exchanges
(Thompson, 1969) and triadic levels were soon after included (Kummer, Götz, &
Angst, 1974). Few years later polyadic perspectives to study social interactions
were emphasized and these exchanges were considered essential to fully
understand social groups (Colmenares & Rivero, 1986; de Waal & van
Roosmalen, 1979).
The traditional PC/MC approaches to analysing conflict resolution
strategies provided valuable information about social exchanges at dyadic and
triadic levels and have also allowed for a systematized methodology in which
several important issues regarding the consequences of agonistic encounters
have been addressed (Aureli & van Schaik, 1991; Aureli, van Schaik, & van Hooff,

15. 15
1989; Castles & Whiten, 1998; Cordoni, Palagi, & Tarli, 2006; de Waal &
Yshihara, 1983; Kappeler & van Schaik, 1992; Palagi & Norscia, 2015;
Preuschoft, Wang, Aureli, & de Waal, 2002; Swedell, 1997; Webb, Franks,
Romero, Higgins, & de Waal, 2014; Zhao et al., 2016). The conclusions regarding
the function of affiliative PCIs in reducing post-conflict stress, repairing the
damage caused by the conflict, and signalling the end of conflicts are some of
the main contributions of these conventional PC/MC methods (Aureli & van
Schaik, 1991; Baker & Aureli, 1997; de Waal, 1986a; Koski, 2015; Palagi &
Norscia, 2015; Preuschoft et al., 2002; Silk, 1997; Watts, Colmenares, & Arnold,
2000; Webb et al., 2014). However these methods acknowledged that some
interactions were being neglected, those performed by others in the group and
that could modify the meaning of the interactions between former opponents.
With the method proposed here the roles can change during the conflict and a
conflict only ends when no one aggresses, therefore a wider range of behaviours
are being considered and a fuller appreciation of how conflicts are managed is
gained.
We are aware that that several authors previously recognized that
interactions are not isolated events and that these are related to other social
dynamics, and so are conflicts. The main contribution of this research is rolling
out a system that allows the study of these dynamics to provide a general idea
about how conflicts are managed during conflicts themselves. Implementing this
system also permits the comparison of behaviours across the non-conflict, the
conflict and the post-conflict periods. Besides, this method allows for the study of
the PC periods given that polyadic interactions can be split into its dyadic
components and PC periods can be obtained for some dyads by following each
opponent during several minutes after conflicts. However, matched control
methods are not specifically chosen and so the baseline can be obtained from
dyadic interactions during non-conflict periods. Finally, with the proposed coding
system comparisons between species or groups with variations on their
demographic conditions are possible.
Group size may be a constraint for the use of this method. In larger groups
where all individuals are difficult to monitor simultaneously, other alternatives may

16. 16
be selected as, for instance, choosing sub-sets of individuals on the basis of
spatial proximity, visibility, or by those sharing a physical environment or being at
a certain proximity distance. For this same reason, the selection of behaviours to
be recorded should be selected and pre-determined with caution. We are also
aware that the lack of a MC period precludes the study of CCT as it has been
done to date.
We believe that this method is especially adequate for studies in captivity
for several reasons. First, in captive settings the group size is usually smaller
compared to wild conditions, making it easier to monitor all or most individuals at
the same time. Second, in captivity individuals are easier to observe due to space
restrictions. As a matter of fact, in captivity the side effect of dyadic aggression
on other group members may be intensified as a result of space constraints
providing an interesting environment to analyse social exchanges. And finally,
since in captivity individuals have more limited options to avoid escalated
aggression due to the fact that they can’t leave the group, this setting provides
an opportunity to study how individuals cope with and manage conflicts in those
environmental conditions.
3.3 Study 3: Conflict management strategies in groups of chimpanzees and
gorillas: a comparative study.
In the all-male colony of chimpanzees studied here we found that 1) their
social relationships fell between the tolerant to despotic dominance styles. They
established linear and steep dominance relationships, dominants aggressed
more and subordinates acknowledged their lower position through subordination
signals, both during and outside of conflict contexts. Dominance relationships
were reinforced through mild to moderate aggressions, although we failed to find
that dominants emitted also more high intensity aggressions. 2) Grooming
exchanges were likely to be important for maintaining social cohesion. Grooming
was mainly emitted and received by higher-ranking males. Our results also
suggest that grooming was valuable by itself, thus, it was reciprocated instead of
being interchanged for support and, indeed, support was also reciprocated. 3)

17. 17
Using the recording and coding system we found neither reconciliations between
opponents nor victim-initiated consolations. However, we still found clear power
asymmetries, and victims mainly submitted to aggressors following aggressions.
hird parties neither intervened against aggressors nor against victims. We also
found that chimpanzees were stressed after conflicts and they displayed self-
directed behaviours, apparently they managed this stress through grooming
exchanges.
In the all-male group of gorillas studied here 1) we failed to classify males’
interactions into the four graded dominance style scale. As predicted, aggressive
interactions were well balanced, although we still found power asymmetries in
winning conflicts and the losers indeed emitted subordination signals to winners
during conflicts. We also failed to find a relationship between dominance rank
and aggressive exchanges. We suggest that winning conflicts might be the result
of individual differences in fighting abilities. 2) Males played with each other, but
contrary to mountain gorillas, they did not socialize through any other type of the
so-called socio-positive exchanges. 3) The analysis of conflicts with the coding
system revealed that conflicts were highly bidirectional and dyadic, both
aggressors and victims aggressed, counter-aggressed and re-aggressed each
other. Neither reconciliations, consolations, interventions from third parties nor
side directed behaviours were observed in this group. We neither found increased
self-directed behaviours nor playful exchanges after conflicts, suggesting that
stress did not increase after conflicts.
Compared to chimpanzees, conflicts were more bidirectional in gorillas,
whereas in chimpanzees aggressors were dominants over victims and the latter
victims actively recognized aggressors position, in gorillas victims mainly counter-
aggressed and the outcome of conflicts was often undecided. Social contact was
reduced among male gorillas compared to male chimpanzees, chimpanzees
aggressed less to each other and exchanged more socio-positive behaviours but,
contrary to our predictions, they also emitted more stress responses.

18. 18
4. REFERENCES
Arnold, K., & Whiten, A. (2001). Post-conflict behaviour of wild chimpanzees (Pan
troglodytes schweinfurthii) in the Budongo forest, Uganda. Behaviour, 138(5),
649-690.
Arnold, K., & Whiten, A. (2003). Grooming interactions among the chimpanzees of the
Budongo forest, Uganda: Tests of five explanatory models. Behaviour, 140(4),
519-552.
Aureli, F., & de Waal, F. (2000). Natural conflict resolution: University of California
Press Ltd.
Aureli, F., & van Schaik, C. (1991). Post‐conflict Behaviour in Long‐tailed Macaques
(Macaca fascicularis): II Coping with uncertainty. Ethology, 89(2), 101-114.
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(1), 39-51.
Baker, K., & Aureli, F. (1997). Behavioural Indicators of Anxiety: an Empirical Test in
Chimpanzees. Behaviour, 134, 1031-1050.
Boesch, C., & Tomasello, M. (1998). Chimpanzee and human culture. Current
Anthropology, 39, 591-614.
Byrne, R., & Whiten, A. (1997). Machiavellian intelligence. Machiavellian intelligence
II: Extensions and evaluations, 1-23.
Castles, D. (2000). Triadic versus dyadic resolutions: cognitive implications. In F.
Aureli & F. De Waal (Eds.), Natural conflict resolution (pp. 289-291). Berkley:
University of California Press.
Castles, D., & Whiten, A. (1998). Post-conlict behaviour of Wild Olive Baboons. I.
Reconciliation, redirection and consolation. Ethology, 104, 126-147.
Colmenares, F. (2006). Is postconflict affiliation in captive nonhuman primates an
artifact of captivity? International Journal of Primatology, 27(5), 1311-1336.
Colmenares, F., & Rivero, H. (1986). A conceptual model for analysing social
interactions in baboons: a preliminary report. In P. Colgan & R. Zayan (Eds.),
Quantitative Models in Ethology (pp. 63-80). Toulouse: Universitat Paul
Sabatier, Privat.
Cordoni, G., Palagi, E., & Tarli, S. (2006). Reconciliation and consolation in captive
western gorillas. International Journal of Primatology, 27, 1365-1382.
Cords, M. (1997). Friendships, alliances, reciprocity and repair. Machiavellian
intelligence II. Cambridge University Press, Cambridge, 24-49.
de Waal, F. (1986a). Conflict resolution in monkeys and apes. In K. Benirsche (Ed.),
Primates: the Road to Self-sustaining Populations (pp. 341-350). Berlin:
Springer.
de Waal, F. (1986b). The integration of dominance and social bonding in primates.
Quarterly Review of Biology, 61, 459-479.
de Waal, F. (1989). Food sharing and reciprocal obligations among chimpanzees.
Journal of Human Evolution, 18(5), 433-459.
de Waal, F. (1997). The Chimpanzee's service economy: Food for grooming. Evolution
and Human Behavior, 18(6), 375-386.
de Waal, F. (2000). Primates--a natural heritage of conflict resolution. Science,
289(5479), 586-590.
De Waal, F., & Tyack, P. (2009). Animal social complexity: intelligence, culture, and
individualized societies. Harvard: Harvard University Press.

19. 19
de Waal, F., & van Roosmalen, A. (1979). Reconciliation and consolation among
chimpanzees. Behavioral Ecology and Sociobiology, 5, 55-66.
de Waal, F., & Yoshihara, D. (1983). Reconciliation and redirected affection in rhesus
monkeys. Behaviour, 85(3), 224-241.
Dunbar, R. (1988). Primate social systems. London: Chapman & Hall.
Dunbar, R. (1989). Social systems as optimal strategy sets: the costs and benefits of
sociality. Comparative socioecology, ed. V. Standen & R. Foley. Blackwell
Scientific.[arRIMD].
Dunbar, R. (1998). The social brain hypothesis. brain, 9(10), 178-190.
Hemelrijk, C., Meier, C., & Martin, R. (1999). Friendship for fitness in chimpanzees?
Animal Behaviour, 58(6), 1223-1229.
Henzi, S., Lycett, J., & Weingrill, T. (1997). Cohort size and the allocation of social
effort by female mountain baboons. Animal Behaviour, 54(5), 1235-1243.
Hinde, R. (1983). Primate social relationships: an integrated approach: Blackwell
Scientific Oxford.
Howell, S., Schwandt, M., Fritz, J., Marzke, M., Murphy, J., & Young, D. (2006).
Effects of early rearing history on growth and behavioral development in captive
chimpanzees (Pan troglodytes) Nursery rearing of nonhuman primates in the
21st century (pp. 313-350): Springer.
Kappeler, P., & van Schaik, C. (1992). Methodological and evolutionary aspects of
reconciliation among primates. Ethology, 92(1), 51-69.
Koski, S. (2015). Reconciliation and Peace‐Making: Insights from Studies on
Nonhuman Animals. In R. Scott & S. Kosslyn (Eds.), Emerging Trends in the
Social and Behavioral Sciences: An Interdisciplinary, Searchable, and Linkable
Resource (pp. 1-15).
Kummer, H., Götz, W., & Angst, W. (1974). Triadic differentiation: an inhibitory
process protecting pair bonds in baboons. Behaviour, 49(1), 62-87.
Lee, P. (1999). Comparative primate socioecology (Vol. 412). Cambridge, UK:
Cambridge University Press.
Mitani, J., Merriwether, D., & Zhang, C. (2000). Male affiliation, cooperation and
kinship in wild chimpanzees. Animal Behaviour, 59(4), 885-893.
Mitani, J., Watts, D., Pepper, J., & Merriwether, D. (2002). Demographic and social
constraints on male chimpanzee behaviour. Animal Behaviour, 64(5), 727-737.
Noe, R., de Waal, F., & van Hooff, J. (1980). Types of dominance in a chimpanzee
colony. Folia Primatol (Basel), 34(1-2), 90-110.
Palagi, E., & Norscia, I. (2015). The season for peace: reconciliation in a despotic
species (Lemur catta). PloS one, 10(11), e0142150.
Preuschoft, S., Wang, X., Aureli, F., & de Waal, F. (2002). Reconciliation in captive
chimpanzees: a reevaluation with controlled methods. International Journal of
Primatology, 23(1), 29-50.
Silk, J. (1997). The function of peaceful post-conflict contacts among primates.
Primates, 38(3), 265-279.
Standen, V., & Foley, R. (1989). Comparative socioecology: The Behavioural Ecology
of Humans and Other Mammals (Vol. 8). Oxford: Oxford University Press.
Swedell, L. (1997). Patterns of reconciliation among captive gelada baboons
(Theropithecus gelada): A brief Report. Primates, 38(3), 325-330.
Thompson, N. (1969). The motivations underlying social structure in Macaca irus.
Animal Behaviour, 17, 459-467.

20. 20
Watts, D. (1990). Mountain gorilla life histories, reproductive competition, and
sociosexual behavior and some implications for captive husbandry. Zoo Biology,
9(3), 185-200.
Watts, D., Colmenares, F., & Arnold, K. (2000). Redirection, consolation, and male
policing: How targets of aggression interact with bystanders. In F. Aureli & F.
de Waal (Eds.), Natural Conflict Resolution (pp. 281-300). Berkeley: University
of California Press.
Webb, C., Franks, B., Romero, T., Higgins, E., & de Waal, F. (2014). Individual
differences in chimpanzee reconciliation relate to social switching behaviour.
Animal Behaviour, 90, 57-63.
Zhao, H., Li, J., Wang, X., Zhang, J., Wang, C., Qi, X., Guo, S., Wang, R., Shi, K., &
Wang, X. (2016). Postconflict behavior among Rhinopithecus roxellana leader
males in the Qinling Mountains, China. Current Zoology, 62(1), 33-37.