Spoiled Brats: Is Extreme Juvenile Agonism in Ring‐Tailed Coatis (Nasua nasua) Dominance or Tolerated Aggression?

Ring‐tailed coatis exhibit an extreme form of juvenile agonism not found in other social mammals. Two groups of habituated, individually recognized, coatis were studied over a 2.5‐yr period in Iguazu National Park, Argentina. Dominance matrices were divided by year and group, resulting in four dominance hierarchies which were analyzed using the Matman computer program. Strong general patterns were seen in both groups during both years. Adult males (one per group) were the highest ranking individuals, followed by male juveniles, female juveniles, adult females, and male and female subadults. The pattern in which young, physically inferior individuals were able to outrank larger adults is different from other social mammal species in that the juvenile coatis aggressively defended food resources and directed aggression towards older individuals. These agonistic interactions may not reflect ‘dominance’ in the traditional sense, and appear to be a form of ‘tolerated aggression.’ This tolerated aggression leads to increased access to food, and should help juveniles during a period in which they need to rapidly gain weight and grow. Because this tolerance of juvenile aggression is reinforced through coalitionary support of juveniles by adult females, agonistic patterns are also consistent with the hypothesis that juvenile rank is being influenced by high degrees of relatedness within coati groups. Although some interesting parallels exist, there is little evidence indicating that these dominance patterns are the same as those found in other social mammals such as hyenas, lions, meerkats, or Cercopithicine primates.     

Sex differences in the social behavior of wild spider monkeys (Ateles geoffroyi yucatanensis)

Competition for resources and the need for cooperation are reported to affect patterns of social interactions and thus the quality of social relationships in primates. Relationships may be described as high quality when both individuals behave in a way that benefits their partner. We investigated the distribution of a wide range of social behaviors across sex partner combinations of adult spider monkeys with specific reference to contested resources. Data were collected from two communities of wild spider monkeys (Ateles geoffroyi yucatanensis) in the Otoch Ma'ax Yetel Kooh reserve in Yucatan, Mexico. Affiliative behavior was exchanged most frequently between males, and as male-male aggression was rare, male-male social relationships were characterized as high quality. Female-female social relationships were best described as low quality as females showed no preference to be in proximity with other females and female-female affiliative behavior was rare. Relationships between the sexes generally were characterized by high rates of female-directed male aggression, although additional investigation into the effects of kinship and female reproductive state on male-female relationships is required before further conclusions can be drawn. Dyadic and coalitionary female-female aggression was significantly higher than expected in a feeding context, confirming that female spider monkeys primarily compete for access to food. Male-male aggression did not increase significantly when in the presence of females, but males embraced at higher rates when in mixed-sex subgroups. As embraces serve to reduce the likelihood of aggression during tense situations, high rates of male-male embraces in mixed-sex subgroups may mitigate male conflicts over access to females.     

Patterns of coalition formation by adult female baboons in Amboseli, Kenya

Coalitionary support in agonistic interactions is generally thought to be costly to the actor and beneficial to the recipient. Explanations for such cooperative interactions usually invoke kin selection, reciprocal altruism or mutualism. We evaluated the role of these factors and individual benefits in shaping the pattern of coalitionary activity among adult female savannah baboons, Papio cynocephalus, in Amboseli, Kenya. There is a broad consensus that, when ecological conditions favour collective defence of resources, selection favours investment in social relationships with those likely to provide coalitionary support. The primary features of social organization in female-bonded groups, including female philopatry, linear dominance hierarchies, acquisition of maternal rank and well-differentiated female relationships, are thought to be functionally linked to the existence of alliances between females. Female savannah baboons display these characteristics, but the frequency and function of their coalitionary aggression is disputed. In our five study groups, 4-6% of all disputes between females led to intervention by third parties. Adult females selectively supported close maternal kin. There was no evidence that females traded grooming for support or reciprocated support with nonkin. High-ranking females participated in coalitionary aggression most frequently, perhaps because they derived more benefits from group membership than other females did or could provide support at lower cost. Females typically supported the higher ranking of two contestants when they intervened in disputes between subordinates, so most coalitions reinforced the existing dominance hierarchy. Results indicate that female baboons participate in coalitionary aggression in a manner strongly influenced by nepotism and individual benefits.     

Sociality in Callithrix penicillata: II. Individual Strategies During Intergroup Encounters

In social animals, intergroup interactions, whether through agonistic and competitive behaviors or affiliative ones, can influence important parameters such as home range, territory sizes, and access to resources, which may directly affect both female and male fitness. We studied the intergroup interaction patterns of a wild group of black-tufted-ear marmosets (Callithrix penicillata) in central Brazil. Agonistic interactions occurred at low frequencies during intergroup encounters. The marmosets directed agonistic interactions without physical aggression primarily against same-sex individuals, suggesting that male and female aggression patterns are shaped by their sexual interests. However, females of the focal group also directed agonistic behavior toward extragroup males that attempted copulation. The marmosets appeared to use intergroup encounters to gather information about possible partners and extragroup reproductive opportunities. Intergroup sexual interactions occurred mainly in the form of copulations or attempted copulations by all adults, with the exception of the dominant female. Our results suggest that a possible reproductive strategy used by males is to attempt fertilization of extragroup females. Adult males copulated with the same extragroup female during several opportunities, which suggests sperm competition or the establishment of social bonds with neighboring females.     

Detecting instability in animal social networks: genetic fragmentation is associated with social instability in rhesus macaques

The persistence of biological systems requires evolved mechanisms which promote stability. Cohesive primate social groups are one example of stable biological systems, which persist in spite of regular conflict. We suggest that genetic relatedness and its associated kinship structure are a potential source of stability in primate social groups as kinship structure is an important organizing principle in many animal societies. We investigated the effect of average genetic relatedness per matrilineal family on the stability of matrilineal grooming and agonistic interactions in 48 matrilines from seven captive groups of rhesus macaques. Matrilines with low average genetic relatedness show increased family-level instability such as: more sub-grouping in their matrilineal groom network, more frequent fighting with kin, and higher rates of wounding. Family-level instability in multiple matrilines within a group is further associated with group-level instability such as increased wounding. Stability appears to arise from the presence of clear matrilineal structure in the rhesus macaque group hierarchy, which is derived from cohesion among kin in their affiliative and agonistic interactions with each other. We conclude that genetic relatedness and kinship structure are an important source of group stability in animal societies, particularly when dominance and/or affilative interactions are typically governed by kinship.     

Socio-genetic correlates of unbiased sex dispersal in a population of black capuchin monkeys (<Emphasis Type="Italic">Sapajus nigritus</Emphasis>)

Most social mammal species exhibit male-biased dispersal. Sex bias in dispersal leads to a higher degree of relatedness among individuals of the philopatric sex, thus an atypical dispersal pattern might lead to deviations in the typical within-group kinship structure. Kinship, in turn, influences patterns of social interactions, as widely evident by kin-biased behaviors. We investigated the link between dispersal, relatedness structure, and sociopositive interactions established by adult females of black capuchin monkeys (Sapajus nigritus) living in a population that experiences female dispersal, an unusual pattern for capuchin monkeys. The study was conducted in Parque Estadual Carlos Botelho (PECB), within the Brazilian Atlantic Forest. We addressed dispersal and relatedness patterns by genotyping 20 adults of 3 groups across 9 microsatellite loci. We also sampled the monkeys’ behavior and compared spatial association frequencies and rates of grooming among same- and opposite-sex dyads. There was no difference between males and females in genetic parameters; both males and females show low coefficients of relatedness indicating that neither sex is consistently philopatric. The mean pairwise coefficient of relatedness for co-resident females was not higher than that for co-resident males. Compared to other populations of capuchin monkeys, female bond was weak, as evident by lower spatial association frequencies, reduced rates of grooming and lack of correlation between coefficients of relatedness and measures of dyadic sociopositive interactions. Our findings thus confirm that female dispersal is a habitual process in the capuchin population of PECB, and that, as expected, dispersal by females strongly influences the relatedness structure of the population as well as the affiliative relationships among female groupmates.     

Inter-individual relationships in proboscis monkeys: a preliminary comparison with other non-human primates

This is the first report on inter-individual relationships within a one-male group of proboscis monkeys (Nasalis larvatus) based on detailed identification of individuals. From May 2005 to 2006, focal and ad libitum data of agonistic and grooming behaviour were collected in a forest along the Menanggul River, Sabah, Malaysia. During the study period, we collected over 1,968 h of focal data on the adult male and 1,539 h of focal data on the six females. Their social interactions, including agonistic and grooming behaviour, appeared to follow typical patterns reported for other colobines: the incidence of social interaction within groups is low. Of 39 agonistic events, 26 were displacement from sleeping places along the river, 6 were the α male threatening other monkeys to mediate quarrels between females and between females and juveniles, and 7 were displacement from feeding places. Although the agonistic behaviour matrix based on the 33 intra-group agonistic events (excluding events between adults and juveniles and between adults and infants) was indicative of non-significant linearity, there were some specific dominated individuals within the group of proboscis monkeys. Nonetheless, grooming behaviour among adult females within a group were not affected by the dominance hierarchy. This study also conducted initial comparisons of grooming patterns among proboscis monkeys and other primate species. On the basis of comparison of their grooming networks, similar grooming patterns among both-sex-disperse and male-philopatric/female-disperse species were detected. Because adult females in these species migrate to groups repeatedly, it may be difficult to establish the firm grooming exchange relationship for particular individuals within groups, unlike in female-philopatric/male-disperse species. However, grooming distribution patterns within groups among primate species were difficult to explain solely on the basis of their dispersal patterns. Newly immigrated females in some species including proboscis monkeys are eager to have social interactions with senior group members to improve their social position.     

Counter aggression and reconciliation in Assamese macaques (Macaca assamensis)

Patterns of aggressive and affiliative behavior, such as counter aggression and reconciliation, are said to covary in the genus Macaca; this is referred to as the systematic variation hypothesis. These behavior patterns constitute a species dominance style. Van Schaik's [1989] socioecological model explains dominance style in macaques in terms of within- and between-group contest competition. Dominance style is also said to correlate with phylogeny in macaques. The present study was undertaken to examine phylogenetic and socioecological explanations of dominance style, as well as the systematic variation hypothesis. We collected data on counter aggression and reconciliation from a habituated group of Assamese macaques (Macaca assamensis) at the Tukeswari Temple in Assam, India. The proportion of agonistic episodes that involved counter aggression was relatively low. Counter aggression, however, occurred more often among males than among females, and it was most common when females initiated aggression against males. The conciliatory tendency for this group of Assamese macaques was 11.2%. The frequency of reconciliation was low for fights among males and for fights among females, but reconciliation was particularly rare for opposite-sexed opponents. Female social relationships were consistent with the systematic variation hypothesis, and suggest a despotic dominance style. A despotic dominance style in Assamese macaques weakens the correlation between dominance style and phylogeny in macaques, but it is not inconsistent with the socioecological model. Male-female relationships were not well explained by the despotic-egalitarian framework, and males may well have more tolerant social relationships than do females. Sex differences need to be considered when categorizing species according to dominance style.     

Seasonal Changes in Male Associative Behavior and Subgrouping of Alouatta palliata on an Island

Howler groups are usually spatially cohesive and stable in composition; however, more flexible grouping patterns occur in some social groups. We analyzed the associative and subgrouping patterns of males living in a group with fission-fusion social organization. Based on information from previous studies on Alouatta palliata and other primates and in the current socioecological models, we established initial predictions on the variations in male behavior according to several socioecological factors. We studied associative behavior via scan sampling at 15-min intervals to register the identity of males in the subgroups and the presence and number of receptive females. We calculated an association index that was then transformed into a measure of association strength. We found individual association trends, as well as important seasonal differences in the subgrouping patterns of males. During the dry season the presence of many receptive females resulted in reduced levels of association, and therefore fewer males per subgroup. The scenario changed during the wet season, when males grouped together significantly more and kinship relationships were a major determinant for individual association preferences.     

Effects of food,proximity, and kinship on social behavior in ringtailed lemurs

Efforts to understand the variation in primate social systems and their underlying interaction patterns have focused on both intrinsic and extrinsic factors. In the socioecological model, food distribution and abundance have been argued to be the primary influences on the social behavior of primate species. We examined the relationship of food resources and two intrinsic factors—kinship and proximity—with patterns of affiliative and agonistic relationships in two semi‐free ranging ringtailed lemur, Lemur catta, social groups (N=14) at The Duke Lemur Center in Durham, NC. In analyzing these three factors concurrently within the same system, we attempt to establish their relative power in explaining the characteristics of social relationships. Patterns of affiliation and high‐intensity agonism were best explained by kinship. Proximity also explained affiliation but did not explain agonism, which varied considerably between groups. The influence of food on social interactions was highly variable between the two groups and, therefore, did not convincingly account for the social behavior patterns we observed. Finally, different intensities of agonism have different patterns and should be analyzed individually. The variation between social groups makes it difficult for us to conclude that any one factor is primarily and universally responsible for patterns of social behavior in this species. Am. J. Primatol. 72:981–991, 2010. © 2010 Wiley‐Liss, Inc.     

Neighbor effect: evidence of affiliative and agonistic social contagion in captive chimpanzees (Pan troglodytes)

Previous studies of captive chimpanzees have demonstrated the "neighbor effect," or social contagion, with respect to agonistic vocalizations and behaviors. The present study considers whether there is a relationship between behavior patterns in focal animals and the auditory signals of neighboring social groups. Using focal-group sampling, we collected 172.5 hr of data on 51 subjects (25 females and 26 males) housed in 10 social groups. We performed two-tailed Wilcoxon matched-pairs signed-rank tests to determine whether the relative frequency of the vocalizations (high vs. low) affected the behaviors. In keeping with past research, we found that agonistic noises and vocalizations from neighboring social groups had a significant effect on the rates of focal-group bluff displays, pant-hoots, and aggression (P<0.05). In addition, we also found significant relationships between grooming behavior and vocalizations in focal groups, and grooming vocalizations from neighboring groups (P<0.05). The results suggest that social contagion is not limited to aggressive behaviors, but also occurs for affiliative behavior patterns.     

Agonistic Interactions of Juvenile Savanna Baboons

19 juvenile members of known genealogies in two wild baboon groups were studied over a 16-month period to compare the ontogeny of agonistic experience and dominance relations for males and females. Juveniles of all age-sex classes were disproportionately likely to receive aggression from and submit to adult males per unit of time spent in proximity. This pattern intensified with increasing juvenile age. With age, juvenile females more often submitted to unrelated adult females from higher-ranking families, whereas this was not true for juvenile males. All juveniles received aggression from older group members more often during feeding than was expected by chance. High rates of agonistic interaction with unrelated adult females accounted for old juvenile females (3–5.5 years-old) interacting agonistically more frequently than male age peers and young juveniles of either sex (1–2.5 years-old). Adult females were also more aggressive toward females among young juveniles, suggesting that adult females target females among juveniles for aggression and resistance to rank reversal. Within juvenile age groups, males dominated all females and all younger males, irrespective of maternal dominance status. Dominance relations among female age-peers were generally isomorphic with relations among their mothers. No juvenile targeted any older male for rank reversal. Males targeted all older females, whereas females typically targeted only older females from families lower-ranking than their own. The strong sexual dimorphism in adult body size in baboons may explain why juvenile males' dominance relations with peers and adult females are not structured along lines of family membership as is true for the less dimorphic macaques. Acquisition of higher agonistic status probably allows juveniles of both sexes to increase their success in within-group feeding competition during late stages of juvenility, which, in turn, could affect important life-history traits such as age at menarche and adult body size.     

Changes in social interactions during adolescence in male mandrills (Mandrillus sphinx)

The adolescent period in male mandrills extends from the time the testicles descend (at the age of 3-4 years) to the time adult characteristics develop (at the age of 10 years), and is thus one of the longest adolescent periods in cercopithecines. In this short cross-sectional study of 11 male mandrills (4.7-9.1 years old), we analyzed social behavioral patterns to investigate partner preference and changes in types of interactions throughout puberty. The mandrills were separated into two clusters on the basis of all of the social interactions scored, as well as the age and sex of the protagonist. During early to mid puberty, immature individuals interacted preferentially with other male adolescents and juveniles. Playing was an important activity, and some affiliative interactions with juveniles were observed. Older adolescents interacted more with adult males and females. These older adolescents were predominantly aggressive toward other adolescents, females, and juveniles, and showed little or no affiliative or playful behaviors. These results indicate a shift in social partners: older males interacted more frequently with adult males, and their behavior involved more aggression and less submission compared to younger adolescents, which showed predominantly submissive and playful behavior. These changes are consistent with preparation for dispersal and future intermale competition.     

Patterns of dominance and affiliation in wild pig-tailed macaques (Macaca nemestrina nemestrina) in West Sumatra

Patterns of agonistic and nonagonistic behaviors were studied in a troop of wild pig-tailed macaques in West Sumatra, Indonesia. The animals were provisioned and the identities of all adult and adolescent individuals were known. The females could be divided into high-, mid-, and low-ranking subsets of individuals. Most grooming occurred within, instead of between members of these subsets. The members of each subset also tended to feed together at the baiting sites, and they probably represented groups of close kin. Among females, grooming appeared to be a conciliatory behavior and was generally performed by the subordinate partner, while mounting was performed by the dominant partner and appeared to be a reassertion of dominance. High-ranking males tended to form agonistic alliances with females and to exchange grooming with estrous females. Low-ranking males did not have such associations with females and were frequently the targets of agonistic alliances of females and juveniles. Mounting between males appeared to be a conciliatory behavior. It seemed effective since severe aggression between males was not observed. The subordinate partner mounted more frequently than the dominant one, but the direction of mounting was apparently controlled by the latter. This suggests that, among pig-tailed macaques, the dominant male plays an important role in the coexistence of males in the troop.     

Feeding Competition and Agonistic Relationships Among Bwindi <Emphasis Type="Italic">Gorilla beringei</Emphasis>

Testing predictions of socioecological models, specifically that the types of feeding competition and social relationships female primates exhibit are strongly influenced by the distribution, density, and quality of food resources, requires studies of closely related populations of subjects living under different ecological conditions. I examined feeding competition and the resulting female social relationships in mountain gorillas (Gorilla beringei beringei) of Bwindi Impenetrable National Park, Uganda, which has ecological conditions distinctive from those where other gorilla populations live. I observed 1 group of gorillas for 29 mo to examine the proportion of time spent foraging on fruit, the relationship between patch size and occupancy patterns of fruit trees, and agonistic interactions. Patch occupancy time while foraging in fruit trees decreased with increasing number of gorillas in a tree and decreasing tree size, suggesting that fruit trees represent limiting patches and can lead to intragroup scramble competition. Gorillas exhibited higher levels of aggression while feeding on fruit versus other food resources, which indicates intragroup contest competition. I observed a linear dominance hierarchy with no bidirectionality via displacements, and a similar hierarchy via aggression, though a notable proportion of the dyads contained 2-way interactions. However, most aggression was of low intensity (vocalizations) and the recipient typically ignored it. Despite differences in ecological conditions and diet between the Virunga Volcanoes and Bwindi, agonistic relationships among females are largely similar in the 2 populations and are best characterized as dispersal individualistic.     

Hormonal regulation of agonistic and affiliative behavior in female mongolian gerbils (Meriones unguiculatus)

Ovarian steroids and oxytocin (OT) have been implicated in the regulation of social behaviors. The purpose of the present study was to examine hormonal substrates of aggression and affiliation in the female Mongolian gerbil (Meriones unguiculatus), a highly social, monogamous rodent. Sexually naive adult females were paired with sexually experienced males for 48 h and their interactions videotaped. Females were gonadally intact and tested during vaginal estrus (INT) or ovariectomized and observed after the following treatments, administered by means of sc injections: EBEB (7 days of estradiol-benzoate); EBP (2 days of EB followed by progesterone), SALEB (saline, days 1-5 then 2 days of EB), OTEB (OT for days 1-5 then 2 days of EB); OTOIL (OT for days 1-5 then 2 days of OIL); or SALOIL (saline days 1-5 then 2 days of OIL). During the first hour of pairing INT females displayed higher levels of affiliation and lower levels of sniffing and agonistic behavior than SALOIL females. All hormonal treatments reduced agonistic behaviors when compared to SALOIL, although none of the hormonal treatments restored affiliation to INT levels. During the 48-h test overt aggression varied by treatment with INT, EBEB, EBP, and OTEB females displaying lower levels than SALOIL, while all groups displayed similar levels of affiliation. The results indicate that OT and E play a significant role in regulating male-directed aggressive behavior in females and that the presence of ovarian hormones as well as OT can increase affiliation during initial contact. Over a sustained period of cohabitation social cues appear to be more important in regulating affiliation than gonadal hormones.     

个体亲近程度对藏酋猴攻击行为的影响

友好和冲突行为决定了群居动物的社会结构及其表现形式,表现为个体间近距差异。但目前尚不清楚藏酋猴个体间亲近关系的差异性是否会影响冲突和攻击的强度。本研究于2020年9月至2021年5月对栖息于安徽黄山的藏酋猴鱼鳞坑YA1群进行跟踪观察,采用目标动物取样法采集行为数据,全事件记录法用于攻击行为数据的补充,分析个体间近距、理毛和攻击行为矩阵的关系,并采用GLMM模型探讨攻击行为的影响因素。结果显示：藏酋猴个体间近距指数越大,理毛时间越长;个体间近距指数矩阵与攻击总次数、轻度攻击和重度攻击次数矩阵均呈显著正相关;个体间亲近关系越紧密,攻击次数和强度越大,但相较雄性间和异性间,雌性间攻击次数和强度最小。这些结果表明,个体间近距持续时间会增加理毛和攻击行为的可能性,雌性个体间社会关系更稳定,但并未发现藏酋猴根据个体间亲近关系调整攻击强度。本研究为进一步了解多雌多雄的藏酋猴群体的社会关系和社会结构提供了数据支持。     

Male-male Interactions in Heterosexual and All-male Wild Mountain Gorilla Groups

Variation in male dispersal and behavior patterns are components of intraspecific differences in social systems. A comparison of male behavior in different social settings can be useful for determining which behavioral mechanisms contribute to variability in social systems. Two heterosexual multimale groups and one all-male group of mountain gorillas (Gorilla gorilla beringei) were observed for over 1100 h at the Karisoke Research Centre, Rwanda. Data on proximity patterns, dominance relationships, aggression, agonistic interventions, affiliation, and homosexual behavior were compared among the males in these groups to examine the influence of female presence, sex ratio, group size, and kinship on male—male interactions. Males in the all-male group stayed closer together, affiliated more, exhibited more homosexual behavior, and were more aggressive toward each other than males in heterosexual groups. However, the males in heterosexual groups showed more wounding and more consistent dominance relationships. Kinship did not influence male-male relationships in the all-male group. The males in the heterosexual groups rarely interacted with one another; they may actively avoid close proximity to reduce aggression. Results suggest that the variable social system of mountain gorillas may be more strongly influenced by demographic factors, male-female social relationships, and male-male competition for mates than by any benefits of male-male relationships.     

Agonistic behavior and dominance relationships in female Phayre's leaf monkeys -- preliminary results

Socioecological theory suggests a link between the strength of competition for food/safety, rates of agonism, structure of dominance hierarchies, and dispersal among group-living females. This study presents preliminary data on agonistic behavior and dominance relationships for female Phayre's leaf monkeys (Trachypithecus phayrei), a species in which females routinely disperse. Behavioral observations were conducted on two groups (four adult females, and five adult females plus two juvenile females, respectively) at Phu Khieo Wildlife Sanctuary, northeast Thailand. Rates of agonistic behavior were analyzed from focal continuous recordings, while dominance hierarchies were constructed from all agonistic behaviors (focal and ad libitum sampling). Overall, female-female agonistic behaviors (aggression, submission, and displacements) occurred at a rate of < 0.25 interactions per hour. Agonistic interactions involving food occurred more frequently than expected based on feeding time. Females in both groups exhibited linear dominance hierarchies with some reversals, and possibly an age-inversed hierarchical structure in the larger group. The results fit well with previous results for colobine monkeys regarding frequency of interactions, displacements predominating agonistic behavior, and the possibility of an age-inversed hierarchy. The results contradict the suggested link between linearity of hierarchies and female philopatry. Future studies should consider the notion that female dispersal may coexist with linear dominance hierarchies.