Distribution Of Grooming Research Articles

Does rank rule? Rank-related grooming patterns in Nicobar long-tailed macaques Macaca fascicularis umbrosus.

Primates maintain social bonds with specific individuals in the group by directing grooming toward them. Social grooming is often targeted toward individuals with whom the most benefits can be exchanged, which are usually the high-ranking individuals. We used the Seyfarth model to investigate whether dominance rank alters the distribution of grooming in a group of Macaca fascicularis umbrosus at Great Nicobar Island. We investigated whether dominance rank predicted grooming rate in both males and females. We used social network analysis to examine whether high-ranking animals maintain a central position in the grooming network. We also investigated whether adult individuals exchange grooming for social tolerance, as indicated by physical proximity. We found that more social grooming was directed toward high-ranking females, but not high-ranking males. Social network analysis suggested that high-ranking animals are not central individuals in the distribution of grooming; rather, middle-ranking animals were major contributors to the distribution of grooming. There was no relation between the grooming rate and proximity in both males and females. Overall, our findings suggest that females prefer to direct grooming toward high-ranking partners, although the dominance hierarchy is less steep than expected for Macaca fascicularis. Thus rank-related grooming patterns may be a relatively conserved trait in this isolated island population.

Do males bond? A study of male-male relationships in Nicobar long-tailed macaques Macaca fascicularis umbrosus

In primates, males compete for a mate, which is a non-sharable resource. This makes the conditions less conducive for males to have stable relationships. One such special kind of relationship is a bond where the interactions are reciprocated, equitable and differentiated. Bonds in macaque societies are based on the degree of within-group contest competition for mates which is dependent on the synchronization of female fertile phase and reliability of fertility signals. Species of the Fascicularis group, including Nicobar subspecies, show intermediate reliability in the signals with mild peaks, and studies have shown reciprocity but no differentiation. We conducted a study on a group of wild Nicobar long-tailed macaques Macaca fascicularis umbrosus to understand the existing patterns of male-male relationships. We examined whether there is reciprocity in affiliation among the individuals and whether the rate of affiliation is balanced. We also measured the dominance linearity and steepness in the group to understand the monopolizability of females. We used social network analysis to understand whether the relations are differentiated based on hierarchical position and whether the high-ranking individuals are the most central individuals in the distribution of grooming in the group. We found that there is reciprocity among the males although that is not equitable. There was no rankrelated differentiation of affiliation among the males of the group. Instead, the identities of individuals influenced affiliation patterns. Our results correspond to the existent strong relationships but lack of social bond otherwise found in the Fascicularis group of macaques.

Early life experience and alterations of group composition shape the social grooming networks of former pet and entertainment chimpanzees (Pan troglodytes).

The long-term effects of early life adversities on social capacities have been documented in humans and wild-caught former laboratory chimpanzees (Pan troglodytes). However, former pet and entertainment chimpanzees have received little attention to date. This study aimed to investigate the long-term effects of early life experience on 18 former pet and entertainment chimpanzees, based on social grooming data collected at a primate rescue centre over a 12-year period. Moreover, we also focused on the possible short-term effects that alterations to group composition might have on grooming patterns. For this purpose, we compared stable and unstable periods (i.e. where alterations to group composition occurred). We used two individual social network measures to analyse the grooming activity and the distribution of grooming among group mates for each individual. We could show that wild-caught chimpanzees were significantly more selective regarding their grooming partners and spent less time grooming when compared to their captive born companions. We also found that individuals who were predominantly housed without conspecifics during infancy spent less time grooming compared to those who were predominantly housed with conspecifics during infancy. Furthermore, we found that alterations to the group composition had short-term effects on the distribution of social grooming from a more equal distribution during periods with a stable group composition towards a more unequal and selective distribution during unstable periods. Thus, we conclude that the social grooming networks of former pet and entertainment chimpanzees are shaped not only by long-term effects such as early life experience, but also by short-term effects such as alterations to group composition. Remarkably, we found not only captive born chimpanzees but also wild-caught individuals to adjust their grooming to socially challenging situations by modifying their grooming distribution in a similar way.

Competition for grooming partners and interference in affiliation among female mandrills

AbstractGrooming is the most common primate affiliative behaviour, and primates compete for accessing grooming partners. We studied a captive group of mandrills (Mandrillus sphinx) to evaluate the role of different types of competitive interactions in shaping the distribution of grooming among females. Mandrill females preferentially groomed high‐ranking individuals, but low‐ranking females were less able to do so. Interference in others’ grooming and a (consequent) reluctance of low‐ranking females to access dominant group mates occurred frequently and contributed to the observed pattern of grooming distribution, while takeovers of grooming partners was relatively rare. Interference in others’ affiliation was possibly used to prevent the formation of revolutionary alliances. Difficulties in accessing individuals already engaged in grooming exerted a strong but rank‐independent effect on grooming interactions. These results highlight the role of competition in determining access to preferred social partners.

Evidence of direct reciprocity, but not of indirect and generalized reciprocity, in the grooming exchanges of wild Barbary macaques (Macaca sylvanus).

Reciprocity is one of the mechanisms that have been proposed to explain the exchange of social behaviors, such as grooming, in animals. Reciprocity assumes that individuals act as the donor and recipient of grooming and switch roles over time to balance the benefits and costs of this behavior. Three main patterns of reciprocity may follow a grooming given: (i) direct reciprocity, where the former recipient returns the grooming to the former donor; (ii) indirect reciprocity, where another individual returns the grooming to the former donor; and (iii) generalized reciprocity, where the former recipient returns the grooming to another individual. While there is evidence that direct reciprocity plays an important role in various species of animals, the role of indirect and generalized reciprocity is less clear and has been rarely analyzed. We tested the role of direct, indirect, and generalized reciprocity in explaining grooming exchanges of wild Barbary macaques, by analyzing the temporal contingency between giving and receiving grooming. We collected the occurrence and latency of the three types of grooming reciprocation during 1 hr long focal sessions run simultaneously on two partners who just stopped grooming (post-grooming session) or who were in proximity (i.e., within 1.5 m) without grooming each other (control session). We ran the analyses on 284 post-grooming and 63 control sessions. The results revealed a temporal contingency of grooming interactions exchanged according to direct reciprocity but not according to indirect or generalized reciprocity. Our results indicate that grooming distribution in Barbary macaques is partner-specific. We discuss the possible role of cognition and emotions in explaining direct reciprocity in animals.

Intermediate-term emotional bookkeeping is necessary for long-term reciprocal grooming partner preferences in an agent-based model of macaque groups.

Whether and how primates are able to maintain long-term affiliative relationships is still under debate. Emotional bookkeeping (EB), the partner-specific accumulation of emotional responses to earlier interactions, is a candidate mechanism that does not require high cognitive abilities. EB is difficult to study in real animals, due to the complexity of primate social life. Therefore, we developed an agent-based model based on macaque behavior, the EMO-model, that implements arousal and two emotional dimensions, anxiety-FEAR and satisfaction-LIKE, which regulate social behavior. To implement EB, model individuals assign dynamic LIKE attitudes towards their group members, integrating partner-specific emotional responses to earlier received grooming episodes. Two key parameters in the model were varied to explore their effects on long-term affiliative relationships: (1) the timeframe over which earlier affiliation is accumulated into the LIKE attitudes; and (2) the degree of partner selectivity. EB over short and long timeframes gave rise to low variation in LIKE attitudes, and grooming partner preferences were only maintained over one to two months. Only EB over intermediate-term timeframes resulted in enough variation in LIKE attitudes, which, in combination with high partner selectivity, enables individuals to differentiate between regular and incidental grooming partners. These specific settings resulted in a strong feedback between differentiated LIKE attitudes and the distribution of grooming, giving rise to strongly reciprocated partner preferences that could be maintained for longer periods, occasionally up to one or two years. Moreover, at these settings the individual’s internal, socio-emotional memory of earlier affiliative episodes (LIKE attitudes) corresponded best to observable behavior (grooming partner preferences). In sum, our model suggests that intermediate-term LIKE dynamics and high partner selectivity seem most plausible for primates relying on emotional bookkeeping to maintain their social bonds.

Whom to groom and for what? Patterns of grooming in female Barbary macaques (Macaca sylvanus).

Grooming is one of the most conspicuous social interactions among nonhuman primates. The selection of grooming partners can provide important clues about factors relevant for the distribution of grooming within a social group. We analyzed grooming behavior among 17 semi-free ranging female Barbary macaques (Macaca sylvanus). We tested whether grooming is related to kinship, rank and friendship. Furthermore, we tested whether grooming is reciprocated or exchanged for rank related benefits (i.e. lower aggression and increased tolerance whilst feeding). We found that in general grooming was reciprocally exchanged, directed up the hierarchy and at the same time affected by friendship and kinship. Grooming was more frequent among individuals with higher friendship values as well as amongst related individuals. We also divided our data set on the basis of rank difference and tested if different power asymmetries between individuals affected the tendency to exchange grooming for rank related benefits and grooming reciprocation. In support of our initial hypothesis our results show that the reciprocation of grooming was a significant predictor of grooming interactions between individuals of similar rank, but not between those individuals more distantly separated in the social hierarchy. However, we did not find any evidence for grooming being exchanged for rank related benefits in either data set. Our results, together with previously published studies, illustrate the behavioral flexibility of macaques. It is clear that multiple studies of the same species are necessary to gather the data required for the solid comparative studies needed to shed light on patterns of grooming behavior in primates.

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.

Grooming and the value of social relationships in cooperatively breeding meerkats

In social mammals, grooming is used not only for hygienic purposes; it also serves social functions. We examined the grooming patterns of dominant males in groups of cooperatively breeding meerkats, Suricata suricatta, to test the hypothesis that the distribution of grooming reflects the value of social relationships. Grooming between dominant individuals was the most commonly observed interaction. Grooming by the dominant male was less common when the dominant female was in oestrus. Grooming between dominant males and subordinates was asymmetrical, with dominant males receiving more grooming and providing less grooming to subordinates. Because subordinate males defend the group against extragroup males, the dominant male was predicted to groom subordinate males more often than to groom subordinate females. Although the sex of a subordinate did not affect the probability of grooming occurring, dominant males groomed subordinate males for longer than they groomed subordinate females. The duration of grooming by a dominant male was longer in small groups than large groups, suggesting that grooming activity is constrained by time. In contrast, subordinates groomed dominant males for longer in larger groups, and as a result, the asymmetry of grooming exchanges was exaggerated in larger groups. This result is consistent with the biological market theory, which predicts that the value of subordinates is dependent on group size and that subordinates will alter grooming efforts accordingly. These results suggest that meerkat grooming serves several social functions, such as the maintenance of valuable and/or fitness-enhancing relationships.

Analysing the effects of group size and food competition on Japanese macaque social relationships

Socio-ecological models predict group size to be one major factor affecting the level of food competition. The aims of this study were to analyse how grooming distribution and reconciliation were affected by differences in group size and food competition in a habitat where predation risk is absent. Data were collected on two groups of different size of wild Japanese macaques (Macaca fuscata yakui), living on Yakushima Island, Japan. The large group faced a greater level of intra-group scramble and a lower level of inter-group food competition. However, intra-group food competition appeared to be greater in the small group as evidenced by the stronger rank-related effects on diet composition in the small group. Grooming and reconciliation were more matrilineally kin-biased and more directed toward close-ranking monkeys in the small group than in the large group. Reconciliation was more frequent in the small group, but monkeys in the large group spent more time grooming and had a greater number of grooming partners. These results indicate that social relationships within the two groups were the result of the combination of group size differences and of the balance between the benefits and costs of a lower/greater level of inter- and intra-group food competition.

Trade-offs in primate grooming reciprocation: testing behavioural flexibility and correlated evolution

Primates may trade altruistic behaviours, such as grooming, either for itself or for different rank-related benefits, such as tolerance or agonistic support. Ecological conditions are expected to affect competition and thus the steepness of dominance hierarchies. This, in turn, may influence the value of the different currencies that primates exchange. Thus, it can be hypothesized that, as the dominance hierarchy becomes steeper, more grooming is directed up the hierarchy (in exchange for tolerance or agonistic support) and less grooming is exchanged for other grooming. We assembled a large database of within-group grooming distribution in primates (38 social groups belonging to 16 species and eight genera) and tested these hypotheses both within species (i.e. comparing different groups of the same species) and between species (using comparative methods that control for phylogenetic relatedness). We found within-species evidence that steeper dominance hierarchies were associated with more grooming being directed up the hierarchy, and that a trade-off occurred between the tendency to groom up the hierarchy and the degree of grooming reciprocation (although, in some analyses, only a nonsignificant trend was observed). By contrast, phylogenetically controlled comparisons between species did not reveal evidence of correlated evolution between the steepness of the dominance hierarchy, the tendency to direct grooming up the hierarchy, and the degree of grooming reciprocation.

Reciprocation and interchange in wild Japanese macaques: grooming, cofeeding, and agonistic support

Social primates spend a significant proportion of their time exchanging grooming with their group companions. Although grooming is mainly exchanged in kind, given its hygienic and tension-reducing functions, it is still debated whether grooming also provides some social benefits, such as preferential access to resources (e.g., food or mating partners). In this study we analyzed grooming distribution among wild female Japanese macaques living in two groups on Yakushima. We tested the tendency of monkeys to reciprocate the amount of grooming received, and to direct their grooming up the hierarchy. Then we analyzed the relation of grooming to three of its possible benefits: reduced aggression, increased tolerance over food, and agonistic support against a male aggressor. The data were analyzed by means of row-wise matrix correlations. Grooming was highly reciprocated (i.e., exchanged in kind) and directed up the hierarchy in both the study groups. No significant relationship was found between grooming and aggression. Conversely, grooming favored tolerance over food, since it was positively correlated with presence on the same food patch, close proximity, and close approaches (both within 1 m) during feeding. Grooming was also positively related to agonistic support against adult males, although this relationship became nonsignificant when we controlled for kinship. Although these results are not definitive, they suggest that monkeys may derive various social benefits from grooming. This conclusion is supported by the fact that in various primate species animals tend to prefer high-ranking individuals as grooming partners.

Seasonal variation in feeding behavior, competition and female social relationships in a forest dwelling guenon, the blue monkey (Cercopithecus mitis stuhlmanni), in the Kakamega Forest, Kenya

Socioecological models relate differences in feeding strategies to variation in the nature of female social relationships. Among the African forest guenons, females consume large quantities of fruit and other plant reproductive parts, resources which are thought to promote contest competition, yet these monkeys have been characterized as having agonistically undifferentiated relationships in which rank, if discernible at all, does not correlate with fitness benefits. To determine whether female relationships become more hierarchical under relevant ecological conditions, we monitored the adult females of two blue monkey groups (Cercopithecus mitis stuhlmanni) over a complete annual cycle in the Kakamega Forest, Kenya. Females competed aggressively for plant reproductive parts more often than any other resource type, and in both groups we detected linear dominance hierarchies. Nonetheless, agonism rates remained low throughout our study, and did not vary with changes in ecological conditions. Rather, when plant reproductive parts were scarce, subordinate females spent more time feeding and less time resting in an apparent attempt to compensate for a reduced efficiency of food intake. The effects of rank and food abundance were not reflected, however, in the distribution of grooming. The use of alternative feeding strategies appeared to blunt competition – females of all ranks were unlikely to be near others while feeding and spent more time consuming alternative resources when plant reproductive parts were scarce. The diverse diet of this species may allow females to avoid conflict so that dominance has only subtle effects that are difficult to detect. While socioecological models often simplify the connection between resources and female interactions, our results emphasize that the behavior of animals consuming particular resources, and not the resources themselves, are critical predictors of social patterns.

ABNORMAL BEHAVIORAL ORGANIZATION OF GROOMING IN MICE LACKING THE VITAMIN D RECEPTOR GENE

Vitamin D is a steroid hormone with several important functions in the nervous system. Numerous human and animal data link alterations in the vitamin D system to various behavioral disorders. Grooming is an important element of rodent behavior with a general pattern of cephalocaudal progression (paw licking – nose/face wash – body wash – tail/genitals wash). Here we studied whether genetic ablation of vitamin D nuclear receptors (VDR) in mice may be associated with altered behavioral sequencing of grooming. Overall, VDR null mutant mice showed abnormal grooming, including a higher percentage of “incorrect” transitions and longer duration of “incorrect” grooming (contrary to the cephalocaudal progression); a higher percentage of interrupted grooming bouts; and the atypical regional distribution of grooming (more leg grooming, less body and tail/genitals grooming), compared to their wild-type controls. Grooming of heterozygous mice was similar to the wild-type group, indicating that abnormal grooming patterning is inherited as a recessive. In contrast, behavioral sequencing of another complex behavior (mating with a female) was unaltered in all three genotypes, suggesting grooming-specific abnormal sequencing in these mutant mice. Our results suggest that a neurosteroid vitamin D and VDR may play an important role in controlling sequencing of grooming in mice, and further confirm the important role of the vitamin D system and VDR in the regulation of behavior.

The grooming analysis algorithm discriminates between different levels of anxiety in rats: potential utility for neurobehavioural stress research

Stress has long been known to affect grooming in rodent species, altering both its activity measures and behavioural microstructure. Since stress disturbs a general pattern of self-grooming uninterrupted cephalocaudal progression, the grooming analysis algorithm (Kalueff and Tuohimaa, Brain Res. Protocols, 2004; 15: 151–8) was previously designed for mice to enable the detection of stress by measuring alterations in grooming microstructure in different test situations. Since mice and rats are known to differ in their behaviours, including grooming, the aim of the current study was to test our approach in rats and evaluate the utility of this method for differentiation between high- and low-stress situations. For this, we have developed the rat grooming analysis algorithm (based on ethological analysis of incorrect transitions contrary to the cephalocaudal rule, interrupted grooming activity and the assessment of the regional distribution of grooming) and applied this algorithm to the light-exposed (high stress) and dark-exposed (low stress) groups of rats. Here, we show that the percentage of ‘incorrect’ transitions between different grooming patterns, the percentage of interrupted grooming bouts and altered regional distribution of grooming (less caudal grooming, more rostral grooming) may be used as behavioural markers of stress in rats. Our results suggest that this method can be a useful tool in neurobehavioural stress research including modelling stress-evoked states, psychopharmacological or behavioural neurogenetics research in rats.

Time-matched grooming in female primates? New analyses from two species

The parcelling model of reciprocity predicts that grooming partners will alternate between giving and receiving grooming within grooming bouts, and that each partner will perform approximately as much grooming as it receives within each bout (‘time matching’). Models of allogrooming based on biological markets theory predict that individuals of lower dominance rank will exchange grooming for tolerance from high-rankers, and therefore an inverse relation will be found between grooming partners' dominance rank distance and how closely they match each other's grooming contributions within each bout. We used weighted logistic regression and weighted least-squares regression to test these predictions using data from female white-faced capuchins, Cebus capucinus, and bonnet macaques, Macaca radiata. Only 5–7% of macaque grooming bouts, and 12–27% of capuchin grooming bouts, were reciprocated. However, (1) the duration of grooming by the first groomer significantly predicted whether the groomee would reciprocate at all, and (2) when bouts were reciprocated, the duration of grooming by the first groomer significantly predicted the duration of grooming by the second groomer. Grooming was most balanced among females of similar dominance ranks. Both the time-matching and rank-related effects were weak, although significant. These results indicate that although some form of time matching may be a general characteristic of grooming in female-bonded primate species, time matching accounts for relatively little of the variation in the distribution of grooming within bouts. We also draw attention to weighted regression as a technique that avoids pseudoreplication while using all available data.

Graded limb targeting in an insect is caused by the shift of a single movement pattern.

Grooming responses are movements of a multi-jointed limb that are targeted toward a stimulus site on the body. To be successful, they require a continuous transformation of stimulus location into a corresponding motor pattern or selection and blending of a subset of cardinal motor patterns. Tactile stimulation of one forewing of a locust elicits characteristic grooming movements of the ipsilateral hind leg. An initial targeted trajectory that moves the tarsus toward the site of stimulation is followed by a cyclic trajectory in the region of the stimulus. We have analyzed both components of this behavior to quantify the relative effects of somatotopic stimulus position and leg start posture on three parameters: initial movement direction, accuracy, and grooming distribution. Accuracy and grooming distribution were significantly affected by the stimulus location but were not influenced by the initial leg posture. Both cues systematically shifted the initial movement direction from the onset of the response. The subsequent cyclic component of grooming movements forms a behavioral continuum with no clustering in joint angle space. We therefore conclude that forewing grooming in locusts is generated by a single movement pattern that is continuously shifted by a sensory cue signaling position on the forewing surface. Both vertebrates and invertebrates can switch between distinct movement forms to groom different parts of their bodies. Our data provide the first evidence that invertebrates, like vertebrates, also have graded control of limb targeting within the somatosensory receptive field of a single form of motor response.

Grooming Interactions Among the Chimpanzees of the Budongo Forest, Uganda: Tests of Five Explanatory Models

AbstractPatterns of allogrooming among the Sonso community of chimpanzees of the Budongo Forest, Uganda, were examined and found to closely resemble those at other study sites. Strong affiliative bonds among males were reflected in high levels of grooming compared with other sex combinations. Adult males groomed, and received grooming most often from, other adult males and also adolescent females which were the only females with regular oestrous cycles during the study. Males had a wider diversity of grooming partners than females and groomed more equitably. However, males concentrated the majority of their effort on a very small number of partners compared with other sites. Grooming reciprocity was found among all age/sex combinations with the exception of adult male-female dyads once immediate reciprocation in the form of synchronous mutual grooming was removed from the analysis. Since grooming among males is thought to play a major role in servicing relationships and agonistic coalitions that can improve dominance status, competition for high-ranking grooming partners was predicted to influence the distribution of grooming among males. Grooming was indeed directed up the male hierarchy and closely ranked males groomed each other more often than those that were distantly ranked. However, when only adult males were considered, rank had little effect on grooming distributions. High rank appeared to influence access to females, but did not attract more female grooming partners. Grooming distributions in this average-sized community did not fit a number of alternative priority of access models which assume competition for high-ranking grooming partners that Watts (2000b) found to have some explanatory value in one very large community of chimpanzees, but not in a smaller, more representative one. Although rank is highly likely to influence coalition partner choice, whether such relationships depend upon strategic grooming partner choices in wild chimpanzees is presently unclear.

Distribution of Grooming Among Adult Females in a Large, Free-Ranging Group of Japanese Macaques

We analyzed grooming episodes recorded among adult females in a large, provisioned, free-ranging group of Japanese macaques (Macaca fuscata) at an individual level. Each female groomed on average 10 of the other 84 females, and 54% of them devoted ≥50% of their grooming to a single female grooming partner, which indicates that most females had grooming interactions with a relatively small subset of available females. Although 65% of the total grooming bouts were between related females, 25% of females disproportionately groomed unrelated females, 22% groomed related and unrelated females equally, and grooming was kin-biased for the remaining 53%. Moreover, 11 of 16 kin-groups included at least one female that groomed unrelated females significantly more often than related females. In 18% of unrelated dyads, grooming was directed down the hierarchy, in 58%, grooming was well-balanced between the two females, and in the remaining 25%, grooming was directed up the hierarchy. The results indicate that although Japanese macaques are considered a despotic species based on their dominance style, this group included some females that showed egalitarian tendencies, i.e., grooming was directed down the hierarchy or was well-balanced, and was directed toward unrelated females as often as or more often than toward related females. The presence of egalitarian individuals might be important to maintain a well-organized, female-bonded group.

Competition and the Exchange of Grooming Among Female Samango Monkeys (Cercopithecus Mitis Erythrarchus)

AbstractCurrent socioecological models argue that multi-female primate groups engaging in co-operative, between-group resource competition (BGC), should have egalitarian social relations that promote cohesion among group members, while those that experience strong within-group competition (WGC) should exhibit nepotistic and despotic social behaviour (van Schaik, 1989; Sterck et al., 1997). Here we investigate the idea that very slight WGC can have strong effects on social relationships, even in 'egalitarian' populations, and that individual responses to ecological conditions may vary among group members. We estimated the intensity of both BGC and WGC and used the Biological Markets model to examine their effects on female dominance and grooming distributions for a group of samango monkeys (Cercopithecus mitis erythrarchus) in a high-density, territorial population. We found high levels of territorial activity consistent with female resource defence, low levels of within-group aggression and only slight effects of contest competition on diet. Individual grooming bouts were reciprocal, with no effects of rank, demonstrating that grooming was not exchanged for feeding tolerance. However, in contrast to other C. mitis populations, female samangos maintained a consistent, linear dominance hierarchy that was reflected in the overall patterns of association and grooming, with high-ranking females receiving more grooming, and lower-ranking females were less likely to take part in territorial activity. Our results support the prediction of the current socioecological model that WGC effects on female relationships will always be greater than the cohesive effects of BGC (Wrangham, 1980; Cheney, 1992), and show that a simple 'egalitarian' description of C. mitis female relationships is insufficient.