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Many white-faced capuchin monkey dyads in Lomas Barbudal, Costa Rica, practise idiosyncratic interaction sequences that are not part of the species-typical behavioural repertoire. These interactions often include uncomfortable or risky elements. These interactions exhibit the following characteristics commonly featured in definitions of rituals in humans: (i) they involve an unusual intensity of focus on the partner, (ii) the behaviours have no immediate utilitarian purpose, (iii) they sometimes involve 'sacred objects', (iv) the distribution of these behaviours suggests that they are invented and spread via social learning, and (v) many behaviours in these rituals are repurposed from other behavioural domains (e.g. extractive foraging). However, in contrast with some definitions of ritual, capuchin rituals are not overly rigid in their form, nor do the sequences have specific opening and closing actions. In our 9260 h of observation, ritual performance rate was uncorrelated with amount of time dyads spent in proximity but (modestly) associated with higher relationship quality and rate of coalition formation across dyads. Our results suggest that capuchin rituals serve a bond-testing rather than a bond-strengthening function. Ritual interactions are exclusively dyadic, and between-dyad consistency in form is low, casting doubt on the alternative hypothesis that they enhance group-wide solidarity. This article is part of the theme issue 'Ritual renaissance: new insights into the most human of behaviours'.

Natural selection has evidently mediated many species characteristics relevant to the evolution of learning, including longevity, length of the juvenile period, social organization, timing of cognitive and motor development, and age-related shifts in behavioural propensities such as activity level, flexibility in problem-solving and motivation to seek new information. Longitudinal studies of wild populations can document such changes in behavioural propensities, providing critical information about the contexts in which learning strategies develop, in environments similar to those in which learning strategies evolved. The Lomas Barbudal Monkey Project provides developmental data for the white-faced capuchin, Cebus capucinus, a species that has converged with humans regarding many life-history and behavioural characteristics. In this dataset, focused primarily on learned aspects of foraging behaviour, younger capuchins are more active overall, more curious and opportunistic, and more prone to inventing new investigative and foraging-related behaviours. Younger individuals more often seek social information by watching other foragers (especially older foragers). Younger individuals are more creative, playful and inventive, and less neophobic, exhibiting a wider range of behaviours when engaged in extractive foraging. Whereas adults more often stick with old solutions, younger individuals often incorporate recently acquired experience (both social and asocial) when foraging. This article is part of the theme issue 'Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals'.

In humans, being more socially integrated is associated with better physical and mental health and/or with lower mortality. This link between sociality and health may have ancient roots: sociality also predicts survival or reproduction in other mammals, such as rats, dolphins, and non‐human primates. A key question, therefore, is which factors influence the degree of sociality over the life course. Longitudinal data can provide valuable insight into how environmental variability drives individual differences in sociality and associated outcomes. The first year of life—when long‐lived mammals are the most reliant on others for nourishment and protection—is likely to play an important role in how individuals learn to integrate into groups. Using behavioral, demographic, and pedigree information on 376 wild capuchin monkeys (Cebus imitator) across 20 years, we address how changes in group composition influence spatial association. We further try to determine the extent to which early maternal social environments have downstream effects on sociality across the juvenile and (sub)adult stages. We find a positive effect of early maternal spatial association, where female infants whose mothers spent more time around others also later spent more time around others as juveniles and subadults. Our results also highlight the importance of kin availability and other aspects of group composition (e.g., group size) in dynamically influencing spatial association across developmental stages. We bring attention to the importance of—and difficulty in—determining the social versus genetic influences that parents have on offspring phenotypes. Research Highlights: Having more maternal kin (mother and siblings) is associated with spending more time near others across developmental stages in both male and female capuchins.Having more offspring as a subadult or adult female is additionally associated with spending more time near others.A mother's average sociality (time near others) is predictive of how social her daughters (but not sons) become as juveniles and subadults (a between‐mother effect).Additional variation within sibling sets in this same maternal phenotype is not predictive of how social they become later relative to each other (no within‐mother effect). [ABSTRACT FROM AUTHOR]

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Many mammalian species display sex differences in the frequency of play behavior, yet the animal literature includes few longitudinal studies of play, which are important for understanding the developmental timing of sex differences and the evolutionary functions of play. We analyzed social play, solitary play, and grooming using an 18‐year data set on 38 wild white‐faced capuchin monkeys (Cebus capucinus) followed since infancy. Rates of each behavior were measured as the proportion of point samples taken during focal follows in which the individual engaged in each behavior. To determine sex differences in these rates, we ran a series of generalized linear mixed models, considering both linear and quadratic effects of age, and chose the optimal model for each of the three behavioral outcomes based on information criteria. Rates of both social play and solitary play decreased with age, with the exception of social play in males, which increased in the early juvenile period before decreasing. Male and female capuchins had different developmental patterns of social play, with males playing more than females during most of the juvenile period, but they did not display meaningful sex differences in solitary play rates. Additionally, males and females had different patterns of grooming over the lifespan: males participated in grooming at low rates throughout their lives, while adult females participated in grooming at much higher rates, peaking around age 11 years before declining. We suggest that male and female white‐faced capuchins may adopt alternative social bonding strategies, including different developmental timing and different behaviors (social play for males vs. grooming for females). Our results were consistent with two functional hypotheses of play, the practice and bonding hypotheses. This study demonstrates that play behavior may be critical for the development of sex‐specific social strategies and emphasizes the importance of developmental perspectives on social behaviors. Research Highlights: Relative to females, immature males had higher rates of social play.There was little to no sex difference in solitary play rates.Young male capuchins seem to bond mainly via play; females bond more via grooming. [ABSTRACT FROM AUTHOR]

Across multiple species of social mammals, a growing number of studies have found that individual sociality is associated with survival. In long-lived species, like primates, lifespan is one of the main components of fitness. We used 18 years of data from the Lomas Barbudal Monkey Project to quantify social integration in 11 capuchin (Cebus capucinus) groups and tested whether female survivorship was associated with females' tendencies to interact with three types of partners: (1) all group members, (2) adult females, and (3) adult males. We found strong evidence that females who engaged more with other females in affiliative interactions and foraged in close proximity experienced increased survivorship. We found some weak evidence that females might also benefit from engaging in more support in agonistic contexts with other females. These benefits were evident in models that account for the females' rank and group size. Female interactions with all group members also increased survival, but the estimates of the effects were more uncertain. In interactions with adult males, only females who provided more grooming to males survived longer. The results presented here suggest that social integration may result in survival-related benefits. Females might enjoy these benefits through exchanging grooming for other currencies, such as coalitionary support or tolerance. [ABSTRACT FROM AUTHOR]

Zahavi's "Bond Testing Hypothesis" states that irritating stimuli are used to elicit honest information from social partners regarding their attitudes towards the relationship. Two elements of the Cebus capucinus vocal repertoire, the "gargle" and "twargle," have been hypothesized to serve such a bond‐testing function. The greatest threat to C. capucinus infant survival, and to adult female reproductive success, is infanticide perpetrated by alpha males. Thus, we predicted that infants (<8 months), pregnant females and females with infants would gargle/twargle at higher rates than the rest of the population, directing these vocalizations primarily to the alpha male. Over 16 years, researchers collected data via focal follows in 11 habituated groups of wild capuchins in Lomas Barbudal, Costa Rica. We found some support for our hypothesis. Infants and females with infants (<8 months) vocalized at higher rates than the rest of the population. Pregnant females did not vocalize at relatively high rates. Infants (age 8–23 months) were the only target group that vocalized more when the alpha male was not their father. Monkeys gargled and twargled most frequently towards the alpha male, who is both the perpetrator of infanticide and the most effective protector against potentially infanticidal males. Research highlights: Capuchin "gargle" and "twargle" vocalizations are hypothesized to test important social bonds.Young infants and mothers "gargle" and "twargle" at the highest rates.The most common recipients of these vocalizations are alpha males, who are the only known infanticide perpetrators. [ABSTRACT FROM AUTHOR]

An important extension to our understanding of evolutionary processes has been the discovery of the roles that individual and social learning play in creating recurring phenotypes on which selection can act. Cultural change occurs chiefly through invention of new behavioral variants combined with social transmission of the novel behaviors to new practitioners. Therefore, understanding what makes some individuals more likely to innovate and/or transmit new behaviors is critical for creating realistic models of culture change. The difficulty in identifying what behaviors qualify as new in wild animal populations has inhibited researchers from understanding the characteristics of behavioral innovations and innovators. Here, we present the findings of a long-term, systematic study of innovation (10 y, 10 groups, and 234 individuals) in wild capuchin monkeys (Cebus capucinus) in Lomas Barbudal, Costa Rica. Our methodology explicitly seeks novel behaviors, requiring their absence during the first 5 y of the study to qualify as novel in the second 5 y of the study. Only about 20% of 187 innovations identified were retained in innovators' individual behavioral repertoires, and 22% were subsequently seen in other group members. Older, more social monkeys were more likely to invent new forms of social interaction, whereas younger monkeys were more likely to innovate in other behavioral domains (foraging, investigative, and self-directed behaviors). Sex and rank had little effect on innovative tendencies. Relative to apes, capuchins devote more of their innovations repertoire to investigative behaviors and social bonding behaviors and less to foraging and comfort behaviors. [ABSTRACT FROM AUTHOR]

It is rare in studies of long-lived animals to know enough about the personalities and early experiences of individuals to use this information to predict their behaviour during major life transitions in adolescence and adulthood. Here, we examine how personality traits and early experiences predict age of natal emigration and timing of first ascent to alpha status in 169 wild male white-faced capuchins studied at Lomas Barbudal, Costa Rica, 75 of whom emigrated and 23 of whom acquired alpha status. Males were more likely to delay natal emigration if they were more extraverted, more neurotic, if their fathers co-resided longer with them, and if there were fewer alpha male turnovers. More extraverted males attained alpha status sooner. [ABSTRACT FROM AUTHOR]

Research on nonhuman primate personality dimensions has focused on a small number of taxa, and little of this work has focused on wild populations. We used ratings to assess personality structure in wild white-faced capuchins (Cebus capucinus) over a 9-year period, using a capuchin-specific rating instru-ment based partly on existing instruments. Adequate levels of interrater reliability were found for 24 of 26 items. A longitudinal analysis found that 15 of these items showed significant rank-order stability from adolescence through early adulthood. Principal components analysis revealed 5 components. Four of these components were recognizable "Big Five" dimensions: Extraversion (E), Openness (O), Neuroticism (N), and Agreeableness (A). A dimension incorporating aspects of high O and high Conscientiousness (C) was labeled Eccentricity. Every dimension except for N showed significant rank-order stability from adolescence through early adulthood. Males were more extraverted, open, neurotic, and eccentric than females, whereas females were more agreeable than males. A cross-sectional analysis revealed that openness and agreeableness declined, whereas eccentricity increased, during adulthood. The item content of capuchin Extraversion and Openness, and the existence of a distinctive Eccentricity dimension, are consistent with known characteristics of capuchin social and ecological adaptations, specifically the central roles of alliances, behavioral innovation, and social learning. [ABSTRACT FROM AUTHOR]

Theory and a growing body of empirical evidence suggest that higher ranking males experience reproductive advantages in group-living mammals. White-faced capuchins ( Cebus capucinus) exhibit an interesting social system for investigating the relationship between dominance and reproductive success (RS) because they live in multimale multifemale social groups, in which the alpha males can have extraordinarily long tenures (i.e. they coreside with daughters of reproductive age). Genetic paternity was determined from fecal samples for 120 infants born into three social groups of wild C. capucinus at Lomas Barbudal Biological Reserve, Costa Rica. Alpha males produced far more offspring than expected by chance, and significantly high Nonac's B indices (a measure of deviation from a random distribution of RS among potentially breeding individuals) were a feature of six out of eight male tenures. The likelihood of the alpha male siring a particular offspring was predicted by the kin relationship between the mother and the alpha male, as well as the total number of males and females in the group. The almost complete lack of father-daughter inbreeding [Muniz et al., 2006] constitutes an impediment to alpha male reproductive monopolization in this population, particularly toward the end of long alpha male tenures. Am. J. Primatol. 72:1118-1130, 2010. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Researchers of “culture” have long been interested in the role of social learning in establishing patterns of behavioral variation in wild animals, but very few studies examine this issue using a developmental approach. This 7-year study examines the acquisition of techniques used to process Luehea candida fruits in a wild population of white-faced capuchin monkeys, Cebus capucinus, residing in and near Lomas Barbudal Biological Reserve, Costa Rica. The two techniques for extracting seeds (pounding or scrubbing) were approximately equal in efficiency, and subjects experimented with both techniques before settling on one technique—typically the one they most frequently observed. In a sample of 106 subjects that had already settled on a preferred technique, the females adopted the maternal technique significantly more often than expected by chance, but the males did not. Using a longitudinal approach, I examined the acquisition of Luehea processing techniques during the first 5 years of life. Regression analysis revealed that the technique most frequently observed (measured as proportion of Luehea processing bouts observed that used pounding as opposed to scrubbing) significantly predicted the technique adopted by female observers, particularly in the second year of life; the amount of impact of the observed technique on the practiced technique was somewhat less significant for male observers. These results held true for (a) observations of maternal technique only, (b) observations of technique used by all individuals other than the mother, and (c) observations of maternal and non-maternal techniques combined. [ABSTRACT FROM AUTHOR]

Studies of kin bias in the distribution of social behaviour in group-living matrifocal species generally underline the importance of bonds among female kin. However, few studies examine either how kin bias may be affected by variation in the availability of kin or the relevance of paternal kin. In this study, we used genetic and behavioural data to analyse correlates of coalition formation, proximity, grooming and dominance relations among female white-faced capuchins over a 10-year period during which the number of adult females in the group varied from 6 to 10. Females sided with the most closely related of two opponents when joining coalitions. Both dominance rank and kinship influenced proximity and grooming patterns. In particular, when group size was small, mean relatedness high and interdyadic variation in relatedness low, rank distance was a better predictor of proximity and grooming than was kinship distance. However, when group size was large, mean relatedness lower and interdyadic variation in relatedness higher, females significantly biased their grooming and spatial proximity towards kin. Dominance rank was not so tightly associated with relatedness as in provisioned female-bonded cercopithecines; females did not follow the ‘youngest sister ascendancy rule’. Full sisters, maternal half sisters and mother–daughter dyads associated at statistically indistinguishable rates, and all associated significantly more often than paternal half sisters. Paternal half sisters did not associate more often than distantly related female–female dyads (r <0.125). These and similar results call into question the general importance of paternal kin ties in wild primates. [Copyright &y& Elsevier]

Researchers studying nonhuman primate vocal repertoires suggest that convergent environmental, social, and motivational factors account for intra- and interspecific vocal variation. We provide a detailed overview of the vocal repertoire of white-faced capuchins, including acoustic analyses and contextual information of vocal production and vocal usage by different age-sex classes in social interactions. The repertoire is a mixture of graded and discrete vocalizations. In addition, there is general support for structural variation in vocalizations with changes in arousal level. We also identified several combined vocalizations, which might represent variable underlying motivations. Lastly, by including data on the social contexts and production of vocalizations by different age-sex classes, we provide preliminary information about the function of vocalizations in social interactions for individuals of different rank, age, and sex. Future studies are necessary to explore the function of combined vocalizations and how the social function of vocalizations relate to their acoustic structure, because social use of vocalizations may play an important role in shaping vocal evolution. [ABSTRACT FROM AUTHOR]

Urine washing (UW) is taxonomically widespread among strepsirhines and platyrrhines, yet its functional significance is still unclear. We used 2274 h of focal follows of 35 adult and subadult wild white-faced capuchins (Cebus capucinus) to test 1) the intergroup signaling, intragroup social signaling, and thermoregulatory hypotheses for UW and 2) the hypothesis that individuals sniff each other's urine and other traces to gather socially significant information. Males engaged in significantly more UW than females. All 5 α-males engaged in more UW than subordinate males did, including 4 α-males that increased their UW rate above that of their male groupmates after their rise to α rank. Males engaged in significantly less UW while in view of other males than at other times. Male-male sniffing rates do not correlate with either aggression rate or dominance rank distance. Urine washing rates did not increase while subjects were in parts of their home range where more intergroup encounters occurred. Urine washing rates were highest early in the morning and late in the afternoon, presumably when temperatures were coolest. The data do not support either the thermoregulatory or social signaling hypothesis. We suggest that experiments with captive capuchins are necessary to resolve the issue of the function of urine washing in the taxon. [ABSTRACT FROM AUTHOR]

Capuchin monkeys (Cebus capucinus) are threatened by several types of predators, including various aerial, arboreal and terrestrial predators. Whenever they encounter one of these threats, capuchin monkeys show different escape strategies and utter one of several types of alarm calls. These alarm calls constitute two acoustic categories, each of which is composed of several subtypes: the first category is composed of alarm calls given in response to aerial predators, humans and other capuchin monkeys, and the second is composed of alarm calls given in response to terrestrial predators and snakes. However, within these two broad categories the different subtypes of alarm calls appeared to show a graded continuum with transitions in between. Therefore, we performed an acoustic analysis to determine whether alarm calls between and within categories are characterized by distinct acoustic features. First, the two broad alarm call categories differed in call structure. Second, alarm calls of the first category, given in response to aerial predators, humans and other monkeys, differed in several acoustic variables and thus may convey context-specific information about the type of threat to listeners. Third, alarm calls of the second category, given in response to terrestrial predators and snakes, also differed in several acoustic variables; however, variants of these alarm calls are also given in response to caiman as well as during highly aggressive interactions between conspecifics and thus may not convey specific information about the type of predator or the threat to listeners. Capuchin monkey alarm calls may therefore have the potential to be functionally referential, general and/or urgency-based signals. Future research using detailed playback experiments with alarm calls and analyses of listeners'' responses is required. [Copyright &y& Elsevier]

The likelihood of reconciliation (defined as preferential peaceful contact among former opponents following conflicts) has been predicted to vary positively with relationship value and compatibility, and negatively with relationship security. Long-term data on wild white-faced capuchins (Cebus capucinus) indicate that dyads consisting of an adult female and an alpha male have high value and compatibility, but low security. Two studies of C. capucinus postconflict (PC) behavior were carried out at Lomas Barbudal Biological Reserve, Costa Rica. One study consisted of 30-min PC and matched control (MC) follows. The second study extracted PC and MC periods from long follows, yielding PC/MC periods averaging 105 min. In study 2, but not study 1, significantly more PC/MC pairs were attracted (former opponents affiliated with each other sooner in the PC period than in the MC period) than were dispersed (former opponents affiliated with each other sooner in the MC period than in the PC period). Reconciliation in study 2 could not be explained as a by-product of former opponents' tendency to seek affiliative contact with conspecifics generally, or of the spatial proximity of opponents following conflicts. Attempted reconciliation was less likely to be followed by renewed aggression when reconciliation attempts were delayed following conflicts. The data were insufficient for a formal test of differences in conciliatory tendency (the difference between the number of attracted and dispersed PC/MC pairs, divided by the total number of pairs) among dyad types to be conducted. Am. J. Primatol. 65:205–219, 2005. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Ten researchers collaborated in a long-term study of social conventions in wild white-faced capuchin monkeys, involving examination of a 19,000-hour combined data set collected on 13 social groups at four study sites in Costa Rica over a 13-year period. Five behavior patterns qualified as social traditions, according to the study's criteria: handsniffing, sucking of body parts, and three types of "games." Some conventions were independently invented in virtually identical form at multiple sites. The extinction of several conventions was observed during the course of the study; it appears that they rarely last longer than ten years. It is hypothesized that the monkeys are using these group- or clique-specific social conventions to test the quality of their social relationships. [ABSTRACT FROM AUTHOR]

Identifies potential foraging traditions in white-faced capuchins (Cebus capucinus) using long-term data from three Costa Rican field sites. Comparison of processing techniques for the same food species across sites; Social learning mechanisms as possible explanation for variation in foraging behavior.

Three questions about female-female relationships remain largely unexplored in female-philopatric platyrrhines. First, to what extent is female dominance status dependent on coalitional support? Second, how stable are female dominance hierarchies over multiyear periods? Third, what is the role of allogrooming in servicing long-term social relationships? We addressed these questions using data collected on Cebus capucinus at Lomas Barbudal and Santa Rosa, over a six-year period. Most female-female coalitions against females reinforced the existing dominance hierarchy, but such coalitions were 3–7 times more frequent at Lomas Barbudal than at Santa Rosa. The Lomas Barbudal group's female hierarchy was highly stable throughout the six years of observation, whereas all three of the intensively observed Santa Rosa groups experienced frequent dominance reversals accompanied by physical aggression. In the Lomas Barbudal group, grooming tended to be directed up the hierarchy, and more closely-ranked females groomed at higher rates than distantly-ranked females, whereas these patterns were not consistently found at Santa Rosa. At both sites, grooming was evenly balanced within 67% of female-female dyads, and mothers of young infants received more grooming than other females did. Females did not spend more of their time grooming each other in groups containing more females than in groups containing fewer females, but they distributed their grooming less evenly among their female groupmates in the largest observed group of females. Some of the intersite differences may be attributable to differences in the rate of female mortality or transfer or both. [ABSTRACT FROM AUTHOR]

A single social group of wild white-faced capuchin monkeys was studied for a period of 26 months at Lomas Barbudal Biological Reserve, Costa Rica. A total of 604 hr of focal animal data was collected on six adult females in a group of 21 monkeys. Females could be ranked in a stable, linear dominance hierarchy. Adult females spent much more time in proximity to other adult females than to adult males. Females groomed other females twice as often as they groomed males, and about 55 times more often than males groomed males. Females tended to groom up the dominance hierarchy, and dyads with smaller rank distances groomed more often. Higher-ranking females nursed infants other than their own at lower rates than did lower-ranking females; however, females nursed infants of females ranked both above and below them. Although lower-ranking females were more likely than higher-ranking females to be the victims of aggression, higher-ranking females were not necessarily more aggressive than lower-ranking females. In 96% of female-female coalitions vs. a female, the victim was lower-ranking than both coalition partners; in the remaining 4%, the victim was intermediate in rank between the two coalition partners. HIgher-ranking female-female dyads formed coalitions more often than did lower-ranking dyads. Those female-female dyads that groomed more frequently also formed coalitions more frequently. The patterning of social interactions indicates that Cebus capucinus at Lomas Barbudal are female bonded. [ABSTRACT FROM AUTHOR]

The original article shows incorrect values for ‘Coef. and Robust SE’ under the heading. [ABSTRACT FROM AUTHOR]

Coalitionary recruitment offers a window into animal social cognition. However, naturally observed coalitionary conflicts are challenging to analyse because the researcher has no control over the context in which they occurred, and observed behaviour patterns are typically consistent with multiple explanations. In this paper we analyse observational data of coalitionary solicitations during conflicts in wild capuchin monkeys, Cebus capucinus. We build upon previous work that focuses on identifying the cues that animals use to solicit allies in agonistic encounters. In contrast to previous studies, we applied a statistical technique that allows us to simultaneously compare different hypotheses regarding which cues animals use and how these cues interact. Our analysis shows that capuchin monkeys use information about both relationship quality and dominance when recruiting allies during conflicts. Monkeys primarily use rank when recruiting an ally, but will also use relationship quality, particularly when the potential ally has low rank. This study provides evidence that nonhuman primates are able to classify other group members using multiple criteria simultaneously. In addition, this paper presents a statistical technique that animal researchers can use to infer decision rules from observational data. • We evaluated factors underlying coalitionary solicitations in capuchin monkeys. • The relative value of rank and relationship quality were analysed in a joint model. • Capuchin monkeys use both rank and relationship quality when recruiting allies. • Capuchin monkeys weigh rank more heavily than relationship quality. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]