Visibility, group size, vigilance, and drinking behavior in coati (Nasua narica) and white-faced capuchins (Cebus capucinus): experimental evidence

I studied the role of visibility on the vigilance behavior of coatis Nasua narica and white-faced capuchins Cebus capucinus in a dry tropical forest in Costa Rica. Vigilance and drinking behavior were observed at a waterhole where the water surface was 2–3 m below ground level for 5 days. Then I provided an artificial water pan of similar size adjacent to the natural waterhole, but level with the ground, and observed the same behaviors. Animals drinking at the natural waterhole had to descend below ground where they could not see above ground, while those drinking from the experimental pan could see approaching predators. Variations in drinking and vigilance behavior were accounted for by site (natural vs. experimental water source) and group size, with site contributing most significantly to variations. Both coatis and capuchins decreased their time to wait at the forest edge before emerging to drink, had more drinking bouts, had longer bout lengths, and decreased their vigilance behavior when they drank at the ground-level waterhole compared to the one below the surface, where their visibility was obscured. For both species, total drinking time increased, and vigilance decreased, with group size. This study demonstrated experimentally that visibility and group size influence drinking and vigilance behaviors. Received: 9 February 2000 / Received in revised form: 3 November 2000 / Accepted: 10 November 2000     

Adult male replacement and social change in two troops of hanuman langurs (Presbytis entellus) at Jodhpur,India

I studied the process of adult male replacement and social change in two one- male troops (B20 and B21) of hanuman langurs (Presbytis entellus)at Jodhpur, India. Male-male competition lasted for about 6 months before the successful takeover of one troop (B20). During that period, five adult males from three neighboring bands (AMB7, AMB9, and AMB10) and a resident male of a neighboring troop (B21) were involved in taking over the troop. The latter male also copulated with six females during his interim residency, which suggests that he may have opportunistically maximized his mating chances with females of a neighboring group. During an intertroop interaction, a 14-month-old female infant of the other troop (B21) was fatally attacked by an adult female of the first troop and the infant eventually died. The attacker may have taken advantage of the disorganization created by male-male competition, perhaps to eliminate a future food competitor. In addition, the first troop gained an additional feeding area from the other troop’s range; it included a sleeping site and a waterhole, indicating that territorial fights during social instability may have led to the expansion of the winner’s resource area.     

Social dynamics of the golden snub‐nosed monkey (Rhinopithecus roxellana): female transfer and one‐male unit succession

Among primates that form multilevel societies, understanding factors and mechanisms associated with the movement of individuals between groups, clans, and one‐male social units offers important insight into primate reproductive and social strategies. In this research we present data based on an 8‐year field study of a multilevel troop of Sichuan snub‐nosed monkeys (Rhinopithecus roxellana) in the Qinling Mountains of China. Our study troop contained 78–126 individuals, and was usually organized into 6–8 one‐male units (OMU). The majority of OMUs were composed of networks of unrelated females and their offspring. We found that 59.7% (43/72) of subadult and adult females in our study troop transferred between OMUs (n=66) or disappeared (n=7) from the troop. In the majority of cases, two or more females transferred together into new OMUs or troops. In R. roxellana, new OMUs formed in several ways. During 2001–2008, 16 adult males appeared in the study troop. Over this period, we observed 13 different males who became harem leaders either by taking over an existing harem or by attracting females from other OMUs into their harem. We also observed four OMUs from a neighboring troop to successfully immigrate into the study troop. The number of individuals in these newly immigrated OMUs was significantly smaller than that number of individuals in resident OMUs. During harem formation, fighting between adult males was rarely observed, and female mate choice appeared to play a crucial role in harem male recruitment and replacement. These results suggest that golden snub‐nosed monkeys are organized in a nonmatrilineal social system. Female mate choice and possibly incest avoidance appear to play important roles in female transfer, male tenure, and OMU stability. Am. J. Primatol. 71:670–679, 2009. © 2009 Wiley‐Liss, Inc.     

Birth-season interactions of adult female Japanese Macaques(Macaca fuscata) without newborn infants

The affiliative interactions of 11 adult female Japanese macaques that did not deliver an infant during the 1981 birth season of the Arashiyama West troop were examined. Consideration was given to the effects of kinship as a structuring element in these birth-season interactions and to the degree of association with various categories of troop members based on age, sex, and (in the case of adult females) whether or not the females were new mothers. Females without infants interacted predominantly with their yearling off-spring, although it was the behavior of the offspring that precipitated the interaction. These females were active in soliciting affiliation with nonkin new mothers, whereas female matrilineal relatives with new infants approached and remained in proximity to them more than did nonrelated new mothers. Females without newborns groomed and approached nonkin infants more than infants within their own matriline, and these infants were predominantly those of females in the highest-ranking matriline of the troop. Adult males were responsible for 40% of all grooming received from nonkin by the females without newborns, and these males approached them significantly more than did other adult females without infants. These patterns demonstrate that the structure of social relationships is influenced by the particular dynamics of troop contexts such as birth seasons, as well as by enduring, broad-based affinities which are less affected by cyclic changes in troop context.     

Infanticide and juvenilicide in Hanuman langurs (Presbytis entellus) around Jodhpur,India

Ten cases of infant killings and 2 cases of juvenile killings were observed in two troops of Hanuman langurs, (Presbytis entellus) around Jodhpur, India. Fatal attacks on infants and juveniles are classified into four categories. The process of infanticide was observed from start to end and is described in detail for 3 cases. The age of the victims ranged from 0.2 to 48 months. The interbirth interval among females whose infants were killed is significantly shorter compared to females whose infants survived. In ourt study, 7 cases support the reproductive advantage hypothesis, that infanticide is an adaptive behaviour to increase male reproductive success. The remaining 5 cases do not fit into the reproductive advantage hypothesis. In these cases, victims are over 8 months old, and as such their deaths could not shorten the interbirth interval. It appears that by killing older infants and juveniles the males obtain an advantage in resource competition for their offspring. An alternative is that new males chase or peripheralise the older infants and juveniles, which leads to 97% predominant uni-male troop structure in Jodhpur.     

Introduction and integration of strangers into captive groups of tufted capuchins (Cebus apella)

We introduced two to four unfamiliar animals into three established groups (N = 6–9 per group) of tufted capuchins (Cebus apella).We present findings on the behavioral consequences of introductions as a function of age, sex, and residency status and long-term consequences for health and reproduction. No morbidity from aggression occurred at the time of introductions or during several months following, and reproduction was not compromised. Activity budgets and patterns of social spacing and interaction were little changed following the introductions except for increases in vigilance behavior, especially by newly introduced adult females. Adult females exhibited the strongest and longest-lasting response to changes in group composition. The results indicate that in this species (1) introductions of adult females can be carried out with acceptable risk to the newcomers provided that careful monitoring occurs, so that the onset of severe aggression instigated by resident females toward new females can be avoided, (2) juveniles can be introduced with minimal risk, and (3) adult males can be introduced into groups lacking resident adult males with minimal risk. Capuchins differ in important ways from the better-studied Old World monkeys in their response to introductions of strangers. The differences are instructive with regard to processes supporting species-typical social structure, which is less overtly hierarchical in capuchins than in macaques.     

Status of Trachypithecus geei in a Rubber Plantation in Western Assam, India

Golden langurs (Trachypithecus geei) are an endangered species in a limited area of Northeast India and Bhutan. They are confined to a forest belt in western Assam between the Manas River in the east, Sankosh in the west and Brahmaputra in the south along the Indo-Bhutan border. Due to habitat destruction, their populations are restricted to fragmented forest pockets, especially in India. We compared data on an isolated population of golden langurs in the rubber plantation of Nayakgaon in the Kokrajhar district of Assam, May 2002 with an earlier census in 1997. We counted a total of 52 individuals in 3 troops in 2002. The average troop size is 17.3 (r = 7–26). The ratio of adult male to adult females is 1:3.16. Of the total population 9.6% were adult males, 21.1% were adult females, 17.3% subadult males, 7.7% subadult females, 19.2% juveniles and 25% infants. In 1997 Srivastava et. al., recorded 38 individuals in 5 troops with an average troop size of only 7.6 . Apparently troop fusion has occurred. The increased population is encouraging.     

Paternal Care in <Emphasis Type="Italic">Propithecus verreauxi coquereli</Emphasis>

Alloparental behavior is documented for several anthropoid primates, but few researchers have investigated the extent or variability of such behavior in prosimians. We report results from a study of male-infant interactions in 2 groups of Coquerel’s sifaka (Propithecus verreauxi coquereli) at the Duke University Primate Center (DUPC). Both groups contained 1 adult pair, 2 juveniles, and a newborn. The adult males exhibited paternal behavior toward their offspring in the form of grooming and holding the infant, though males differed in the amount of time they spent engaged in these activities. Group differences in the proximity maintained between the infants’ parents suggest that the relationship between adult males and females may help account for the variation. The presence of juveniles appeared to diminish paternal behavior in the group exhibiting a higher overall rate of male-infant interaction.     

Wild Capuchins Show Male-Biased Feeding Tool Use

Relatively few studies have explored sex differences in the use of foraging tools among primates other than apes. Although male primates are thought to be more innovative, researchers have reported a female sex bias in the use of feeding tools in wild chimpanzees. We investigate here the nature and extent of sex differences in foraging tool use over 12 mo in a free-ranging group of bearded capuchins (2 males, 5 females, and 3 juveniles) living in the dry Caatinga forests of the Serra da Capivara National Park, Piaui, Brazil. These capuchins used 3 major types of feeding tools: 1) tools for probing; 2) tools for pounding/cracking; and 3) digging stones to extract tubers or roots. Adult males performed 63% (n = 134) of all events of tool use and used tools significantly more frequently than did females, although male bout lengths across all tools (57 s ± 7.9 SE) were equivalent to those of adult females (47.3 s ± 12.6 SE). Both sexes used digging and cracking tools, although at different rates, whereas adult males used sticks to probe for prey and other rewards far more than females. Differential opportunities to use tools were not apparent: >71% of tool-use events occurred on the ground, and males and females spent equal time on the ground. We suggest that sex differences in tool use may function as opportunities for male signaling of investment quality.     

Group size,composition, and reproductive success in wild common marmosets (Callithrix jacchus)

Data from published sources about size and composition of wild common marmoset groups (Callithrix jacchus) were analyzed to see if the number of juveniles in a group is closely related to the number of other group members. Mean group size was 8.7 members including 4.4 adults (1.8 females, 2.5 males), 2.9 subadults, and 1.4 juveniles. The number of juveniles was significantly positively correlated to the number of adult males. Groups with one or two adult males had significantly fewer juveniles (mean: 1:1 juveniles) than groups containing more than two adult males (mean: 2.0 juveniles). Apart from a different number of subadults, results showed obvious similarities between common marmosets and tamarins of the genus Saguinus in size and composition of subgroups of adults as well as the key role of adult males in mediating the reproductive success of a breeding female. Common marmoset females seem to gain direct fitness benefits in increased reproductive success from the presence of a larger number of adult males. Whether or not other group members get fitness benefits depends on the reproductive strategy of adult males (monogamy vs. polyandry), their kinship, and on the genetic relationship of nonbreeders to the offspring of the breeding female. © 1995 Wiley-Liss, Inc.     

Sociological study on the troop fission of wild

During the period from June to July 1983, the Hanyama-A troop of wild non-provisioned Japanese monkeys on Yakushima Island began to show signs of troop fission. Adult females together with their infants and juveniles subdivided into two groups, the Hanyama-K group and Hanyama-M group. After the subdivision, all of the troop males were observed vacillating between these two female groups. During the mating season, non-troop males were also observed moving around the two female groups. After this mating season, one of these non-troop males was found to have entered and become the alpha male in one of the groups, while higher-ranking adult males of the original troop settled into the other group. Each fissioned group was strongly considered to be composed of either high-ranking matrilines or low-ranking matrilines as observed previously in provisioned troops. The dominance relation between the two fissioned groups indicated that dominance rank reversal between these two female kin groups must have occurred during the course of subdivision of the troop. However, different from most previous cases of troop fission, there was no indication that males ever participated in the subdivision of the original female group. This was disrupted not as a result of males' involvement, but only as a result of antagonism among females, which initiated the troop fission. The main factor which appeared to determine when and in which fission group males eventually settled was the competition between the troop males' coalition and non-troop males and their ability to monopolize females. The present process of troop fission suggests a dual strategy between males and females (Wrangham, 1979, 1980) even in the society of Japanese macaques.     

Dominance,grooming, and clasped-sleeping relationships among bonnet monkeys in India

Social relationships, including dominance, grooming, and clasped-sleeping, were studied in a troop of bonnet monkeys (Macaca radiata) at Dharwar, India, the study period lasting two months and a half. Three measurements, the peanut test, the drinking test, and the spatial distribution test, were used to analyze dominance relationships. The peanut test showed a straight linear ranking order among adult males and females; however, among females drinking and spatial distribution orders are slightly different from that of feeding (peanut test). Grooming was observed more frequently between adult female and adult female and was seldom observed between adult male and juvenile female or between juvenile male and juvenile female. Apparently all monkeys tend to groom with females. On the other hand, monkeys of the same sex tend to sleep with each other. It is clear that monkeys select their partners when they groom and sleep.     

Life-history characteristics of a wild population of vervets (Cercopithecus aethiops sabaeus) in Barbados,West Indies

Life history data are presented for a population of vervets, Cercopithecusaethiops sabaeus, in Barbados, West Indies. The data were obtained from two habituated troops and from vervets captured during a large-scale trapping program. Individuals of known age from one troop were weighed periodically, and separate growth curves generated for males and females. The mean weight of captured adult females was 3.3 kg; that of adult males, 5.3 kg. The average age at sexual maturity is estimated at 34 months for females and 60 months for males. Vervets give birth throughout the year, but most infants are born between April and July. The average interbirth interval following a surviving infant is 11.8 months. The mortality of juveniles is heaviest between birth and 2 years of age and decreases thereafter. Males emigrate from their natal troops at sexual maturity and one incident of a juvenile female emigrating is reported.     

Social organization of wild talapoin monkeys

A troop of wild talapoins in Cameroon had 70 members including all age-sex classes. Observed between the birth season and the next mating season, it was habitually divided into subgroups. Subgroups most commonly observed were (1) adult and large juvenile males: (2) adult females with infants, small juveniles, and large juvenile females; (3) medium sized juveniles with a single adult male. Adult females and adult males were rarely sighted together and never seen to interact. From observations of caged groups, predictions are made about the changes in this organization which might be expected during the breeding season. A possible parallel with the ecologically similar squirrel monkey is suggested.     

A study of a black howling monkey (Alouatta caraya) population in northern Argentina

A population of Alouatta caraya in northern Argentina had an ecological density of 130 animals per km². Mean troop size varied from 7.2 to 8.9 individuals, and the ratio of adult males to adult females from 0.58 to 0.51. Infants comprised from 6% to 14% of the population, juveniles from 16% to 21%. These percentages probably vary seasonally in response to a birth peak at the beginning of the dry season. Males were age-graded in multi-male troops. Sexual dimorphism was extreme in this species. Males were all black and averaged 6.7 kg; females were yellow-brown and averaged 4.4 kg. Juvenile males retained the pelage color of the female until approximately 4.5 yr of age and 5 kg in weight. No genital mimicry or exaggeration occurred in this species. Vocalizations of A. caraya were similar to those of A. seniculus, both of which tend to be lower pitched than those of A. palliata.     

Origin and fate of a one-male savanna babbon group formed by fissioning

An adult male chacma baboon,Papio hamadryas ursinus, emigrated from his habituated natal group at age 100 months and joined a neighboring multimale-multifemale group. Subsequently this male, together with eight adult females, all with infants <1 year old, formed a one-male group (OMU). The male was the only adult male in this group for over 200 days. Circumstantial evidence shows that shared parentage of the infants with this male determined which females joined the new group. In addition, 10 juveniles younger than 4.5 years joined the new group. Based upon persistent close physical association, especially at sleeping sites, these juveniles were presumed to be the older independent progeny of the eight adult females. Thus, the founding elements of the new group were the adult male and partial matrilines—mothers, their infants, and their independent juvenile offspring. The OMU status of the group ended with the sequential intrusion of three males known to be low ranking in other groups. The first of these intruders was successful in joining the OMU in spite of the OMU male's earlier successes in rebuffing this and other potentially high-ranking males. Six additional males later entered the fission group during a 6-month interval. Two of them outranked the original male. All additional males present in the last 100 days of observations came from the same group, which was not the group of origin of the females.     

Hematologic Values of Free-ranging Cebus cay and Cebus nigritus in Southern Brazil

We evaluated blood samples obtained from 80 free-ranging healthy capuchins (Cebus cay and C. nigritus) to establish hematological reference values and to assess the influence of sex and age on them. We caught the monkeys in the Paraná River region of Southern Brazil via manual or automatic traps. We anesthetized them intramuscularly with 3.6 mg/kg tiletamine/zolazepam hydrochlorides. After physical examinations, we divided the sample according to sex and age: 26 females (13 adults and 13 juveniles) and 54 males (27 adults and 27 juveniles). We collected blood and determined hematological values via traditional published methods. We analyzed data via 2-way ANOVA to test the effect of sex, age, and interactions between the 2 factors. The packed-cell volume was higher in adult males and the numbers of white blood cells and lymphocytes were higher in juveniles. There is no other significant difference.     

Social Relationships Among Ring-Tailed Lemurs (Lemur catta) in Two Free-Ranging Troops at Berenty Reserve, Madagascar

We observed two free-ranging troops of ring-tailed lemurs at the Berenty Reserve, Madagascar. Kinship affinities in these troops are known only for mothers and their offspring 4 years of age. We attempted to quantify social relationships. Almost all agonistic interactions were dyadic, and triadic agonistic interactions, such as alliances, were very rare. Dominance hierarchies in both sexes in the two troops were not linear. As in cercopithecine monkeys, mothers were dominant over their adult daughters. However, the daughters were not ranked immediately below their mothers. Close proximity and social grooming occurred more frequently between closely related females, such as mother–daughter and sister–sister dyads, than between unrelated females. Frequent-proximity relations also occurred between adult males that had emigrated from another troop and entered the present troop together, even though they did not rank closely to one another. Subordinates were likely to groom and to greet dominants more frequently than vice versa. During group encounters, particular females were involved in agonistic interactions with animals of other troops, regardless of dominance rank. Adult males, regardless of their dominance rank, but not adult females, constantly tried to drive solitary males away.     

Playmate relationships among individuals of the Japanese monkey troop in arashiyama

Observations of play behavior were made on a troop of Japanese monkeys for five months. The troop consisted of 125 animals during the study period. Only 104 animals were observed playing with the troop members while the other 21 animals were never observed playing with other individuals. Two-member play was the most frequent. On the average, a monkey played with 20.7 individuals. A total of 6,068 play bouts were observed. The frequency of play appeared to be affected by age, sex, and degree of relatedness. One-year-old infant males played most with other members and the frequency of play decreased with age. Between monkeys whose disparity of age was less than two years, 5,763 bouts (95.0% of the total) were observed. Moreover, among sameaged monkeys who comprised 10.6% of the possible pair combinations, 2,739 play bouts (45.1%) were observed. Juvenile males played with same-sexed peers more than with opposite-sexed peers, whereas older juvenile females appeared to play with infants of both sexes. Individuals who were related and similarly-ranked tended to play together. There was no apparent preference for animals to play with the offspring of the highest-ranking female. Dominance rank of infnats and juveniles was primarily affected by rank of their mothers and to a lesser extent by play partners. Dominance rank of older juvenile males is more likely to be affected by play partners than females. It may be a critical time for males when they leave their natal troop and join a new troop. The timing of troop shifting by males seemed to be affected by the presence or absence of play-mates. For male Japanese monkeys, play is very important in developing social bonds. Play may act to perpetuate social bonds, enhance the chance of survival, and may contribute to their future reproductive success.     

Life history variables of wild troops of formosan macaques (Macaca cyclopis) in Kenting,Taiwan

A study on population dynamics of wild Formosan macaques (Macaca cyclopis) in Kenting, southern Taiwan, was conducted from March 1985 to August 1990. At first, only one monkey troop was studied. It fissioned in 1987 and both of the daughter troops have been observed since then. Total number of animals increased from 10 to 29 over the years, but the sizes of individual troops have never been more than 20. Seasonality in breeding has been detected: copulations were concentrated in the period from November to January and 75% of all the 28 births occurred between April and June. Time of birth by parous females without offspring from the preceding year was earlier than that of lactating females. Young females gave their first births at 4 or 5 years of age. Total birth rate over the study period was 0.8 infant per female per year. Hunting was the main cause of death while natural mortality rate was low for the animals. There was only one adult male in each troop for most of the time. Troop males in the two daughter troops have been replaced two or three times in the three years by some solitary males that moved around in the area. The reproductive parameters of Formosan macaques in Kenting were found to be more similar to that of rhesus monkeys than to Japanese macaques. And a case of higher reproductive success in a high-ranking matriline was reported.