Social behavior of the wild black-capped Capuchin (Cebus apella)

The author undertook a field survey of the capuchin (Cebus apella) lasting 60 days from December 1976 to January 1977, and determined the basic daily activity of its groups and spacing of group members in the day time. Furthermore, based on studies of various types of interactions between individuals of the groups, he was able to show that (1) decisive rank orders exist both among adults and among sub-adults of both sexes; (2) grooming at the resting time is peculiar to adult males; (3) with quite mild agonistic interactions being maintained, a high tolerance exists between the group members; (4) alpha males represent individuals which can be called leaders of groups; and (5) a strong psychological or spiritual bond exists among the adult males, which can be termed a “male-bond.” Furthermore, according to comparative studies on some adjoining groups, it was found that the group structure is strongly influenced by the individuality or character of the adult males of each group. The present findings are generally in agreement with those forC. apella studied by the author and other researchers in other localities. It can be safely said therefore that these findings are probably common to this species of monkey. Based on a comparison with findings for three other species ofCebus, the author attempts to clarify the points of difference betweenC. apella and these three other species ofCebus from the viewpoint of behavioral science and sociology.     

Maintenance of Multifemale Social Organization in a Group of <Emphasis Type="Italic">Nomascus concolor</Emphasis> at Wuliang Mountain,Yunnan, China

Many short-term studies have reported groups of black crested gibbons containing ≥2 adult females (Nomascus concolor). We report the stability of multifemale groups in this species over a period of 6 yr. Our focal group and 2 neighboring groups included 2 breeding females between March 2003 and June 2009. We also habituated 1 multifemale group to observers and present detailed information concerning their social relationships over a 9-mo observation period. We investigated interindividual distances and agonistic behavior among the 5 group members. The spatial relationship between the 3 adult members (1 male, 2 females) formed an equilateral triangle. A subadult male was peripheral to the focal group, while a juvenile male maintained a closer spatial relationship with the adult members. We observed little agonistic behavior among the adult members. The close spatial relationship and lack of high rates of agonistic behavior among females suggest that the benefits of living in a multifemale group were equal to or greater than the costs for both females, given their ecological and social circumstances. The focal group occupied a large home range that was likely to provide sufficient food sources for the 2 females and their offspring. Between March 2003 and June 2009, 1 adult female gave 2 births and the other one gave 1 birth. All individuals in the focal group survived to June 2009. A long-term comparative study focused on females living in multifemale groups and females living in pair-living groups would provide insight into understanding the evolutionary mechanisms of the social system in gibbons.     

The ontogeny of sex differences in the behavior of patas monkeys

Many studies of sex differences in primates have been based on small experimental groups of peers in which only a limited range of social behavior could be expressed. In addition, the first few months of life are often the focus of such studies, with relatively little attention paid to older juveniles. In this study, 11 male and 9 female juvenile patas monkeys, living in a captive social group with all age-sex classes available, were observed between 1 and 4 years of age. A subset of seven patas monkeys was also observed between birth and 1 year of age. Here, we report the development of sex differences in independence, play, grooming, positioning behavior, and aggression over the juvenile period. Juvenile male patas monkeys played more and in longer bouts than females, but wrestling (rough-and-tumble play) was not more common among males. There were few differences in behaviors directed to male and female juveniles by other group members. Distinct differences emerged only in the behaviors of the juveniles themselves, with females being more active participants in social and aggressive interactions than males. In general, sex differences in patas monkeys show a mixture of patterns, some of which are predictive of adult sex differences and some of which appear to be specific to the particular demands of the juvenile period in this species     

Group unity of chimpanzees elucidated by comparison of sex differences in short-range interactions in Mahale Mountains National Park,Tanzania

Chimpanzees (Pan troglodytes) form multi-male and multi-female unit groups with fission–fusion grouping patterns. Short-range interaction (SRI) plays an important role in the unity of these groups and in maintaining social bonds among members. This study evaluated three models of chimpanzee social structure that differed according to the emphasis each placed on social bonds between the sexes, i.e., the male-only, the bisexual, and the male-bonded unit-group model. I investigated differences in SRI between the sexes among group members in well-habituated wild chimpanzees in Mahale Mountains National Park, Tanzania. I followed six focal adult males and six females, and quantified their respective SRI with other chimpanzees. Except between subordinate males and adult females, adults in general engaged in SRI with about 60–90% of the individuals with whom they made visual contact each day, whether in large or small parties. Although the number of social grooming (SGR) partners was limited, male–male SGR networks were wider than were either male–female or female–female SGR networks among adults. The number of contact-seeking behavior (CSB) partners was also limited, but dominant males had more CSB partners. Adult females mainly interacted by pant-grunt greeting (PGG) with adult males, but tended to do so mainly with the highest-ranking male(s) within visual contact. These results indicated that the social bonds among adult males were essential to group unity. Because of clear male dominance, adult females established peaceful coexistence with all group members despite less frequent SRI with subordinate males by maintaining affiliative social bonds with dominant males, thereby supporting the male-bonded unit-group model. Adult females had many female SRI partners, but these interactions did not involve performing conspicuous behaviors, suggesting that females maintain social bonds with other females in ways that differ from how such bonds are maintained with and between adult males.     

Allomaternal behavior in a group of free-ranging patas monkeys

A free-ranging group of patas monkeys (Erythrocebus patas) containing 18 individually identifiable adult females was observed for approximately 400 hours, equally distributed over two two-month periods corresponding to the breeding and birth seasons, at the La Parguera facility of the Caribbean Primate Research Center. The large number of infants born in the spring and early summer (n = 14) allowed for detailed observations of alloparental behaviors, with a focus on allomothering by the adult females. Seven types of alloparental behaviors were recorded: contact, nuzzling, grooming, agonism, close visual inspection, attempted kidnapping, and kidnapping. Adult females emitted the vast majority of allomaternal behavior, the patterning and frequency of which closely resembled the patterning and frequency of inter-adult female social grooming. Relative dominance status of the participants did not consistently predict the directionality of allomothering. The most commonly observed allomaternal behaviors were contact and nuzzling, which are primarily affiliative behaviors; agonism was rare. Successful kidnapping occurred eight times. Immature monkeys (n = 22) emitted an additional 32 alloparental acts. A propensity towards allomothering by experienced females would be most beneficial to patas infants due to the patas' tendency towards dispersed foraging and rapid flight in the presence of danger. It is possible that direct competition with groups of rhesus macaques for available resources on the island served as a proximal cause for the allomothering observed in this patas group.     

Spatial structure of chacma baboon groups

A method is presented for measuring the location of individuals with respect to the center or perimeter of a primate group. The method estimates an individual’s domain of danger: the area in which a hidden predator is closer to the individual than to other group members (cf. Hamilton, 1971). A domain is determined by the directions and distances of particular neighbors from a given individual. Animals at peripheral locations have relatively large domains, whereas animals at central locations have relatively small domains. Domains of danger were sampled for members of two groups of chacma baboons (Papio ursinus)in northern Botswana, to test for nonrandom spatial patterns throughout the day. Females with infants had significantly smaller domains than did females without infants. Domains also were correlated with social ranks of females;high-ranking females had smaller domains than did low-ranking females, possibly because high-ranking females were more likely to have infant offspring. For adult males, however,domain sizes were not significantly correlated with social ranks. Immigration status of adult males, rather than social rank, better accounted for spatial positioning.     

Nonconceptive Sexual Behavior in Bonobos and Capuchins

Sexual behavior by infecundable females, and by same-sex and adult-immature dyads, occurs in wild and captive bonobos (Pan paniscus). Proposed functions of these behaviors, in social primates generally, include practice, paternity confusion, exchange, and communication as well as appeasement. We used this framework to interpret and to compare observations of sexual behavior in a captive bonobo group and a wild white-faced capuchin (Cebus capucinus) group. In both species, (a) sexual behavior was no more frequent in cycling females than in pregnant or lactating females and (b) same-sex and adult-immature dyads engaged in as much mounting or genitogenital contact as adult heterosexual dyads did. The species differed in that (a) bonobos engaged in sexual behavior 65 times as frequently as capuchins, (b) only bonobos engaged in sexual contact other than ventrodorsal mounting during focal observation, and (c) bonobo sexual contact was concentrated most heavily in socially tense situations in adult female–female dyads, whereas capuchin sexual contact was concentrated most heavily in socially tense situations in adult male–male dyads. These data and published literature indicate that (a) practice sex occurs in both species, (b) paternity confusion may be a current function of C. capucinus nonconceptive sex, (c) exchange sex remains undemonstrated in capuchins, and (d) communication sex is more important to members of the transferring sex—female bonobos and male capuchins—than to members of the philopatric sex.     

Responses to urinary stimuli in pigtailed (Macaca nemestrina) and stumptailed (Macaca arctoides) macaques

Responses to different urine samples were studied in pigtailed (M. nemestrina) and stumptailed (M. arctoides) macaques. Both species exhibited more interest towards urine samples from their own species than neutral stimuli. Responses towards urine samples from other macaque species did not significantly differ from those towards neutral stimuli. In stumptailed macaques, no differential interest was observed between urine samples from a known (the adult male of the group) and an unknown adult male conspecific.     

Intermale relations and troop male membership changes in langurs (Presbytis entellus) in Nepal

Data on intermale social relations and troop membership changes in one Nepalese high-altitude population of free-ranging langurs (Presbytis entellus)are reported here. Data were collected from six troops by three observers and cover 32 months of observations. The predominantly multi-male troops indicate an alternating pattern of exclusions and introductions with gradual adult male replacement. Takeovers and infant killing were not observed. Analysis of adult social behavior records show qualitative and quantitative differences in intrasexual relations, with primarily agonistic social contacts occurring between males. Agonistic encounters between females and between males differ in frequency of occurrence, types of be-haviors used, cause, and consistency in direction of threats between individuals. Individual adult male frequency of interaction with females and immatures varied significantly, with the majority of these interactions occurring between the dominant troop male and other troop members. Data indicate that intermale dominance is a major factor in determining male access to fertile females: This appears to be achieved by either directly excluding males from the troop or effectively “controlling” their inter-actions with troop females. Data from these studies are compared with data from other Presbytis entellusinvestigations. Review of these data suggests that intraspecific variability in intermale social dynamics and type of troop male membership change are correlated with the percentage of nontroop males. It is suggested that environmental pressures resulting in social crowding can be critical in determing the occurrence of takeovers in some populations of Presbytis entellus.     

On the ecology and behavior ofCebus albifrons in eastern Colombia: I. Ecology

A-503 contact-hr study of a 35-member group ofCebus albifrons was conducted in eastern Colombia in 1977 and 1978. The group had a female: male socionomic sex ratio of 2.5:1 and used a home range of 110–120 ha which overlapped the home range of another group ofC. albifrons about 20–30 ha. The animals spent about 80% of their foraging time eating plant material and about 20% of their foraging time eating animal materials. A birth peak at the end of the dry season extending into the wet season was indicated by data available. Attempted predation was recorded by the mustelidEira barbara and the black-and-white hawk-eagleSpizastur melanoleucus. Some association was observed with the red howler monkeyAlouatta seniculus. The group at times spent more than half the day foraging and traveling on the ground, exhibiting a level of terrestriality not reported for other New World primates.     

Ethological study of the social behavior of hybrid baboons betweenPapio anubis andP. hamadryas in free-ranging groups

The male-female and male-male interactions of hybrid baboons betweenPapio anubis andP. hamadryas were analyzed quantitatively in two free-ranging groups in the Awash Valley, Ethiopia. Morphologically, one group (the Kerrayu group) was closer to hamadryas, while the other (the Gorge group) was closer to anubis. The adult males were classified into four categories; i.e., leaders of one-male units, males in pair units (both in the Kerrayu group), males with a closer appearance to hamadryas, and males with an anubis-like appearance (both in the Gorge group). These categories coincided with the morphological gradient from hamadryas to anubis. Social behavior was described in terms of 53 kinds of behavioral elements identified. In both groups, the closer a male was to being hamadryas in morphology, the more frequent was the aggressive behavior it tended to address toward partner females. The patterns of male-female interactions were compared between one-male units and pair units in the Kerrayu group. In one-male units, females responded immediately with obedient behavior to the males' behavior of directing visual attention toward them. In pair units, females responded with affinitive or avoiding behavior to physical contact by males. The flow of male social behavior was resolved into transitions from one behavioral element to another, and the succession rates for all the observed transitions were independently computed within each male category. By comparing the principal pathways of the behavioral sequences between male categories, 31 “basic pathways” were identified, which were presumed to be common to bothP. anubis andP. hamadryas. The basic pathways were composed of four main behavioral categories, i.e.,Contact, Visual-spacing, Aggressive behavior toward females, andAppeasing behavior toward males. In one-male units, transitions fromVisual-spacing toAggressive behavior were clearly recognized, whereas the principal pathways in pair units lacked such transitions. The frequency distributions of behavioral elements among the above behavioral categories were compared among the four male categories. The more prevalent anubis characters were in morphology, the larger was the proportion thatContact behavior occupied in the total amount of social behavior. The more prevalent hamadryas characters were, the larger was the proportion thatVisual-spacing behavior occupied. The leaders of one-male units showed a higher percentage ofAggressive behavior than did males of the other three categories. A conspicuous difference was observed in the percentage ofAppeasing behavior between the Gorge and Kerrayu groups. It appeared that the high frequency ofAppeasing behavior among males in the Kerrayu group contributed to the spatial cohesion of this group. The similarities of morphology, principal pathways, and frequency distribution of behavior were calculated for every combination of the four male categories. The morphological similarities correlated best with the similarities of principal pathways. It is concluded that the sequential structure of the male social behavior was strongly correlated with the genetic background, while the frequency of social behavior itself was subject to factors other than innate behavioral tendencies, such as the characteristics of the social environment and social context.     

Adoption of a Wild orphaned ringtailed lemur infant by natal group members: Adaptive explanations

In December 1992 an infant ringtailed lemur, approximately 7 weeks of age, was orphaned in one of the regularly-censused social groups at the Beza-Mahafaly Reserve, southwestern Madagascar. The infant was initially adopted by a subadult (2 yr-old) male from the group. Continuous-time focal animal data were collected for a 12-hr period, from the time that the infant was retrieved by the young male, in order to document the adoption process. Ten members of the infant's social group (total group number=18) engaged in infant care behaviors over the 12-hr period. The subadult male spent the most time engaged in infant care, and he and one adult female exhibited the highest frequency of caregiving behaviors over the 12-hr period (p<0.001). Four adult males also initially cared for the infant. The orphan was one of only six infants in the reserve population to survive that year. She was censused two years later as an adolescent member of her natal group. Adaptive explanations for this adoption vary depending upon the care-giver. For the subadult male and adult female caregivers, kin selection can be suggested, as the infant was related to all females and immature animals in the group. Adult males may have exhibited caregiving behaviors as a strategy related to affiliation with adult females which could lead to potential mating and reproductive success.     

Activity rhythms and use of space of a group ofAotus azarae in Bolivia during the rainy season

A group ofAotus azarae living in an island forest in the Beni region of Bolivia was observed for ten nights during the rainy season of 1985. The three members of the group, an adult male, an adult female, and the young of the year, spent 49.4% of their time resting, 31.7% feeding and 19.8% locomoting. Activity started with low intensity vocalizations about 10–15 min after sunset, the animals returning to the sleeping site in the morning, 10 to 20 min before dawn. Feeding occurred mainly during the early hours of the night, and from 1:30 a.m. to 4:00 a.m. they spent most of their time at rest. The average distance travelled per night was 337.4 m, the monkeys locomoting mainly in the first half of the night. Of the whole of the island forest (0.33 ha), our monkeys used mainly an area of 0.18 ha.     

Social behaviour and infant carrying in a group of moustached tamarins,Saguinus mystax (primates: Platyrrhini: Callitrichidae), on Padre Isla,Peruvian Amazonia

The social behaviour of a group of eight moustached tamarins,Saguinus mystax, (five males, three females) was studied on Padre Isla in northeastern Peru. About 60% of all allogrooming was done by the two adult males in the group, and about 11% by a young adult female. All other group members groomed very little. The adult breeding female received more grooming than any other group member. After the death of the adult female (preyed upon by an anaconda) the amount of active allogrooming remained constant for all group members except for the young adult female, who increased her contribution to about 30%. Her preferred grooming partner was the subadult female, which generally screamed when being groomed by the young adult female and terminated grooming by going away. This kind of grooming relation is termed “forced grooming” and is interpreted as a possible social control mechanism. The young adult female groomed the adult males more often after the death of the adult female than before. This might have had the function of strengthening the social bond with the adult males and in obtaining the breeding position in the group. After the death of the adult female, the vulva of the young adult female grew to full adult size. Agonistic behaviour was less frequent than allogrooming. Most aggressive interactions (50%) originated from the subadult male of the group. The young adult female was the target of most of these aggressions. Extremely little aggression occurred between the three females. The young adult female was the only individual who tried to emigrate from the group during the study period. Her attempt to join a neighbour group failed due to rejection by all four members of this group. All group members participated in carrying an infant, but the adult males and the young adult female carried most frequently. Contribution to infant carrying varied with the infant's age.     

Mating behavior ofXylotrechus pyrrhoderus Bates (Coleoptera: Cerambycidae) V. Female mounting behavior

Female mounting behavior was observed in the grape borerXylotrechus pyrrhoderus Bates (Coleoptera: Cerambycidae) under laboratory conditions. This behavior was directed towards either females (i.e., female homosexual mounting) or males. The female homosexual mounting was strongly elicited in females which had previously been allowed to fly. The frequency of this behavior was not related to the experience of mating. The investigation of the daily temporal pattern in female homosexual mounting activity indicated that the behavior most frequently occurred between 12∶00 and 16∶00, i.e., when females were searching for the pheromone-releasing males. Oviposition was also observed during this time interval. A detailed analysis revealed female mounting behaviors which are characteristic of male mounting behaviors, such as chasing conspecifics and synchronism of licking and abdominal bending. On the other hand, the frequency of male homosexual mounting was lower than that of females. Taken together with cases of other species previously reported, the expression of mounting behavior in females may be related to the evolution of the reproductive system, in which females approach their mates.     

The effects of temporary removal of the alpha male on the behavior of subordinate male vervet monkeys

The effects of temporary removal of the alpha male on the behavior of subordinate adult male vervet monkeys were evaluated. Twelve subordinate males from six captive multimale, multifemale vervet monkey groups were observed in two conditions: when all group members were present and when the alpha male was temporarily removed from each group. In the absence of the alpha male, subordinate males initiated more affiliative behavior and increased the amount of time spent in proximity to females but their rates of aggression were unaltered. Increased affiliative behavior was selectively directed to high-ranking females and their offspring. Under removal conditions, subordinate male behavior did not resemble that of alpha males in intact conditions: they differed in their proximity to and affiliative behavior towards other group members. In the absence of the alpha male, females increased their aggression towards subordinate males. These observations suggest that the presence of alpha males strongly inhibits subordinate males' behavior. When the constraints of the alpha male's presence are removed, subordinate males rapidly engage in behavior that may enhance their likelihood of attaining high rank. In combination with prior studies, the data also indicate that the behaviors involved in the maintenance of high rank by alpha males differ from those subordinates use to acquire dominance. Finally the current study supports the view that aggression by female vervets may be highly influential in determining male ascendency to dominant rank.     

Effects of familiarity on the behaviour towards intruders in captive common marmosets (Callithrix jacchus)

A study on the behaviour of a group of common marmosets (Callithrix jacchus) towards unrelated intruding conspecifics (juvenile male twins) was performed. The group members' proximity to the intruders during two consecutive study periods was analyzed. During the first period in which the experimental conditions as well as the intruders were unfamiliar, all but one group member were equally likely to stay near the intruders and usually more than three individuals were present simultaneously. During the second period the group members showed different scores of proximity towards the intruders. One individual, an adult male, was in close proximity nearly the whole time. Additionally, the number of individuals simultaneously staying near the intruders was clearly reduced. It is argued that (1) the change in behaviour of the group members was affected by the increasing familiarity and (2) intruder experiments with unfamiliar conspecifics are only of partial value for clarification of the process of immigration.     

Observations on the behaviour and ecology of a threatened and poorly known dwarf antelope: the beira (<Emphasis Type="Italic">Dorcatragus megalotis</Emphasis>)

Observations on the behaviour and ecology of the beira (Dorcatragus megalotis) were made during spring 2004 in a wild population discovered in 1993 in a low mountain range in the South of the Republic of Djibouti. Spring was found to be both a birthing and a mating season. Beiras fed in the first and last daylight hours, mainly on dicotyledons and in patches supporting trees and/or bushes. They spent the warmest hours of the day in the shade of trees, or in rock shelters when the temperature became too hot. Observed groups (n = 56) ranged in size from one to five individuals (mean ± SD = 2.70 ± 1.49). Most of these groups included a single adult male (62.5%) or no adult male at all (33.9%). The only encounter observed between two adult males resulted in the chasing of one by the other. Furthermore, the mixed-sex groups including a single adult male seemed rather stable, and their members used collective urination–defecation sites. From a behavioural point of view, the beira thus appears not very far from the dik-diks (Madoqua spp.), but differs from them by a greater sociability between adult females and its type of habitat.     

Affiliative behavior of adult female sooty mangabeys (Cercocebus atys)

A 14-month study of 30 adult female members of a captive group of sooty mangabeys investigated their affiliative interactions with group members of varying age and sex. The adult females preferentially affiliated with other adults and interacted less than expected with immature group members. Dyadic frequencies suggested especially frequent affiliation with the three resident adult males, although the pattern of interaction with each male was distinct and apparently was related to age and dominance status of the males. Females of the alpha matriline showed significantly greater affiliation with the males than did those of other matrilines, but this preference was not reciprocated by the males. A preference for grooming older group members (some of the matriarchs and the oldest adult male) was also suggested. In consideration of the taxonomic distinctness of the sooty mangabey from the gray-cheeked mangabey, comparison of these results with those available for albigena were made. Few differences were apparent. Comparisons with the affiliative behavior of Papio females also suggested limited differences, despite the apparently isolated position of the sooty mangabey within the tribe Papionini.     

Grooming and the Expectation of Reciprocation in Mandrills (<Emphasis Type="Italic">Mandrillus sphinx</Emphasis>)

It is often (implicitly) assumed that the expectation of reciprocation motivates animal altruism, and thus that animals “plan” their social interactions. We tested this hypothesis by studying a captive group of mandrills (Mandrillus sphinx). In our focal group, the alpha male was more likely to provide agonistic support in the minutes after the receipt of grooming than in the absence of previous grooming. This offered other group members the possibility of manipulating the male’s support by grooming him before engaging in an aggression. We used survival analysis to test the hypothesis that the other group members systematically groomed the alpha male just before engaging in aggression, which would suggest that the expectation of reciprocation motivated their grooming. Contrary to the prediction of our hypothesis, we found that other group members did not groom the alpha male just before engaging in aggression, and thus did not benefit from increased support from the most effective ally. These results suggest that mandrills do not plan their social interactions and that the expectation of reciprocation does not motivate them to groom.