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.     

Female rank and reproductive success among arashiyama B Japanese macaques (Macaca fuscata)

Five hypotheses that related female rank and reproductive success were tested in an intact troop of free-ranging, provisioned, Japanese macaques. The hypotheses stated that high-ranking females (1) begin parturition earlier in life than low-ranking females; (2) produce more offspring than low-ranking females; (3) give birth during some optimal time during the birth season to a greater extent than low-ranking females; (4) experience less infant mortality than low-ranking females;and (5) more frequently produce male offspring, while low-ranking females more frequently produce female offspring. A statistical analysis of the data which included three birth seasons and 55 adult females and 34 pubescent females, all of known age, rank, and matrifocal membership in the Arashiyama B troop, revealed few significant results. An association was found between the rank of the matrifocal unit and the age of first birth. However, the relationship was the reverse of hypothesis 1, i.e., females of the lower-ranking matrifocal units began parturition earlier than females of higher-ranking matrifocal units. Therefore, in this troop of Japanese monkeys— where alternative feeding strategies existed— there was little association between female rank and reproductive success.     

The variable social organization of hanuman langurs(Presbytis entellus), infanticide,and the monopolization of females

Data from 24 wild populations of hanuman langurs (Presbytis entellus)in south Asia are used to test hypotheses seeking to explain variation in troop structure and the incidence of infanticide. The occurrence of infanticide is associated with a one-male troop structure and not with a high density. The density, predation, and economic-advantage hypotheses, as explanations for the occurrence of one-male and multimale troops, are not supported by the review. However, the monopolization hypothesis is not contradicted; the number of adult males per troop is significantly correlated with troop size and with the number of adult females per troop. Therefore it is suggested that a one-male troop structure will arise if a male is able to monopolize a group of females, a multimale troop if he cannot. One-male troops may predispose to infanticide because of high variance in male mating success and high intermale competition between groups rather than within troops. If female dispersion determines troop structure, it is speculated that females could manipulate males to form a multimale society if the advantages in terms of infant survival and intertroop conflict exceeded the costs in terms of not producing infanticidal “sexy sons.”     

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.     

Does troop size of wild Japanese macaques influence birth rate and infant mortality in the absence of predators?

For the wild Japanese macaques of Yakushima and Kinkazan Islands, we analyzed the relationship between the troop size or the number of adult females of each troop, infant/adult female ratio (IFR; crude birth rate), and infant mortality (IM) in habitats with no predators. In Yakushima, IFR was positively correlated to troop size and the number of adult females. In Kinkazan, however, IFR tended to decrease with the number of adult females. This difference may be due to the difference in troop size; i.e. in Yakushima, where troop size was small, IFR may increase with that of troop size, because a relatively larger troop is likely to the advantage in intertroop competition. In Kinkazan, where troop size was large, however, IFR is likely to decrease with troop size, because intratroop competition may increase. Thus, the present data roughly supportWrangham's model of the social structure of female-bonded primates, and suggests that there is an optimal troop size for birth rate (BR). On the other hand, there was no clear correlation between IM and the troop size or number of adult females of each troop.     

Infant development in the lion-tailed macaque,Macaca silenus (Linnaeus): The first eight weeks

Infant development in lion-tailed monkeys was observed during the first eight weeks after birth. A rapid decrease in the time spent in the closest association by the mother and the infant was seen between the first and second weeks. Between the second and fifth week there was a somewhat steady state with only marginal decrease in the time spent by the infant out of lap of the mother. However, during this time, a rapid decline in maternal cradling and restraining behaviour was seen. From the sixth week onwards, there was a rapid increase in the time spent by the infant out of contact with the mother. Independence of the infant during troop progression was seen only towards the eighth week, that too only marginal. Among the troop members the subadult females and the juvenile females showed the maximum interest in the infant. The former spent much more time than the juveniles interacting with the infant. The adult females showed only little interest in the infant while the adult male showed no interest at all. Infant snatching by subadult females and juvenile females was seen on many occasions. The infant remained in the possession of them from less than 1 min to more than 2 hr. This behaviour tended to decrease towards the sixth week.     

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.     

The brief survival of free-ranging baboon infants (Papio cynocephalus) after separation from their mothers

The importance of mother — infant attachment in free-ranging primates is illustrated by events culminating in the deaths of two baboon infants a few days after losing their mothers. These two cases are contrasted with those of a severely injured infant, not separated from its mother, which lived, and an animal which lost and refound its troop. Protective behavior of adult males is described. In captivity, separation sometimes produces infant depression; in nature, such depression may be fatal.     

Troop history,female reproductive strategies and timing of male change in Hanuman langurs,Presbytis entellus

Female reproductive data are presented from 9 years of longitudinal observations on two troops of Hanuman langurs (Presbytis entellus) living around Jodhpur, India. On the basis of 89 live births interbirth intervals were calculated to examine the effect of demographic factors on reproductive behaviour and troop composition. Sex of an infant seems to influence the length of intervals which are longer after the birth of female infants at an average of 1.7 months. It is suggested that this may be an outcome of differential maternal investment by allocating more time and energy towards female infants who run a higher mortality risk than male infants, at least up to an age of 27 months. Troopspecific interbirth intervals are influenced by social events. If the last infant is still alive when the next one is conceived, the intervals are significantly longer than after the premature loss of an infant (Bijolai troop: 15.6 vs. 12.1 months; Kailana-1 troop: 16.7 vs. 11.4 months). During undisturbed male tenureship intervals are shorter than after a male change (Bijolai troop: 14.3 vs. 16.0 months; Kailana-I troop: 15.6 vs. 17.5 months). Thus the frequency of male changes can influence the demography of a troop. Furthermore, the data suggest that take-overs are optimally timed by males. New males tend to take over a troop when most of the females are cycling.     

Demographic consequences of a food and water shortage to desert Chacma Baboons,Papio ursinus

The age-sex composition of a chacma baboon (Papio ursinus)population changed following a 5-month interval of extreme food and water shortages. Mortality was significantly greater among adult females, juveniles, and infants than among adult males. The probable basis of 19 of 22 deaths during the interval of food and water shortage was starvation caused by drought conditions which localized water sources, reducing access to food resources. This resulted in a long-term (> 6-year) shift in adult sex ratios within this three-troop population, from 1.04 to 1.42-1.58 adult and subadult males per adult female. Patterns of intertroop interaction were also influenced by food scarcity, which determined which troop was most seriously affected.     

Female-infant interactions among free-ranging stumptail macaques (Macaca arctoides)

The friendly and aggressive behaviors directed by females other than the mother to the troop's infants were recorded during a six-month long study of stumptail macaques living on an island. A great deal of friendly contacts were directed by the females toward the troop's infants. Juvenile females interacted with infants mainly through social play while adult females directed passive contacts (e.g., touch-hand) to them. While the adult females displayed more care contacts toward male infants the juvenile females preferred the female infants. The social position of the infant's mother in the troop and the attention it received from the males regulated the caring behavior an infant received from the females.     

Reproduction in wild female olive baboons

The purpose of this paper is to evaluate several factors that influence female reproduction in a large troop of wild olive baboons (Papio cynocephalus anubis) based on 4 consecutive years of demographic data. Interbirth intervals were significantly shorter for females whose infants died before their next conception than for females whose infants survived. High-ranking mothers of surviving infants had significantly shorter birth intervals than comparable low-ranking mothers, independent of maternal age. This occurred mainly because the interval from resumption of cycling to conception was significantly shorter for high-vs. low-ranking females. Dominance rank did not influence sex ratio at birth, infant survival in the first 2 years, or adult female mortality. Age was also significantly related to interbirth intervals, with older females having shorter intervals. Primiparous females had consistently longer reproductive intervals than did multiparous females, but this difference reached statistical significance only for females whose infants died before the next conception. Primiparous females also experienced significantly higher infant mortality. Data on body size and estrous cycle length indicated no differences between high- and low-ranking females. Nutritional and stress-related mechanisms that may underlie the reproductive advantages of high rank are discussed.     

Infant Killing, Wounding and Predation in Eulemur and Lemur

Infant killing by primates is highly controversial. Sexual selection of infanticidal males has been disputed, especially for seasonally breeding species, in which death of an infant does not advance conception of the next infant. We report attacks, infants found wounded, and predation in seasonally breeding Eulemur and Lemur at Berenty, Beza Mahafaly and Duke University Primate Center, and review cases seen elsewhere. Observed attacks leading to wounds or death conservatively total twelve by extratroop males, two by troop males, and seven by troop females. Eulemur are occasional vertebrate predators, whose prey includes infant Lemur catta. Wounds inflicted by lemurs are usually abdominal canine slashes or bites to the head, with rare eating, a pattern distinct from carnivore and raptor kills. Infant killing as inferred from corpses is more frequent than previously thought, but still rare. Adaptive advantages of killing plausibly include eliminating resource competitors of females, and sexual selection on males.     

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.     

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.     

Affiliative relations among male Japanese macaques (Macaca fuscata yakui) within and outside a troop on Yakushima Island

Male Japanese macaques (Macaca fuscata yakui) in a troop on Yakushima Island frequently groom other males. However, previous studies have not compared the social relations of troop males to those of non-troop males. I followed all troop males and non-troop males in and near a troop during a mating season and during the following non-mating season and recorded their neighbors, grooming, and agonistic interactions. Comparisons of the social relations of troop males and non-troop males with other troop members revealed that grooming and agonistic interactions with females during the mating season were similar between troop and non-troop males. However, troop males groomed each other more often and had fewer agonistic interactions among themselves than did non-troop males. Compared to what occurred in the mating season, troop males groomed females less often and exchanged grooming bouts more often with other troop males during the non-mating season. One non-troop male groomed females more frequently than did any troop male in both seasons, and this male groomed troop males more frequently than did any troop male in the non-mating season. This male immigrated into the troop during the following mating season. Regardless of their competition with respect to reproduction, male Japanese macaques on Yakushima Island maintain affiliative relations, probably to cooperatively defend fertile females from non-troop males.     

Who is Responsible for Fission in a Free-ranging Troop of Baboons?

The study troop of chacma baboons (Papio cynocephalus ursinus) at Mkuzi Game Reserve, Zululand, South-Africa, comprised of about 76 members that split into two new troops. The events leading to this troop fission will be described and its possible causes will be discussed. Troop fission among baboons is generally attributed to the withdrawal of low-ranking females from the main group, as a result of the cost of food competition and its effect on their reproductive success. At Mkuzi, no evidence for food competition among females was recorded in terms of rank-related time spent feeding or other time—budget components, feeding-bout length, diet composition or context of female aggression. Moreover, no evidence for rank-related differential reproductive success was found in terms of inter-birth intervals or infant survival. Female mortality was, however, related to dominance rank, with circumstantial evidence suggesting that cause of mortality was predation by leopards. Rate of female disappearances, aggression levels among females, and the percentage of time they spent in proximity to other adult troop members increased after fission. Relatively short inter-birth intervals and extremely low infant mortality rate at Mkuzi resulted in a small number of receptive females at any one time, and therefore in high costs of male sexual competition as expressed in the high levels of male aggression and woundings, both reduced after fission. It is suggested that this troop fission may have been initiated by the resident males, triggered by the high cost of sexual competition, and forced on the females, who were, consequently, subjected to higher risk of predation. The troop fission was preceded by a long process of increasing tendency for sub-trooping. It was initiated by the four resident males who kept a large distance apart from each other, herded oestrous female associates away from others and were followed by other females. The females generally tended to stay close to associates, males and females. These parties were followed by the peripheral and immigrant males who had no female associates, and eventually two distinct daughter troops were formed.     

Spatial relationships between recent mothers and other troop members in red howler monkeys (Alouatta seniculus)

Data on spatial relationships between eight mothers with young infants and other troop members collected during a study of free-ranging red howlers are used to examine two predictions: (a) that among immature and adult females, individuals showing the greatest interest in young infants are those who would incur the greatest benefit and lowest costs in doing so, and, (b) that since red howler infants may be killed by males, the male who spends most time near an infant is its likely father. Results indicate that females with infants spent less time near the new mother than did immature females and adult females without infants. Those dominant males who were the infant's likely father spent significantly more time near the new mother than did the subordinate males.     

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.     

The role of play in social organization: Comparative observations on squirrel monkeys (Saimiri)

Various functional theories of play stress that social play is essential for the practice and learning of sex roles, dominance relationships, troop culture, integration of individuals into the troop structure, the control of aggression, etc. Data on squirrel monkeys (Saimiri) in natural environments indicate that social interaction and troop integration can develop in various manners in the absence of social play.Comparative observations were made on squirrel monkeys in a seminatural environment in Florida and 43 natural environments in Panama, Colombia, Peru, and Brazil. There was a broad range of variance in the data on ecology, troop size, troop cohesiveness, average individual distances, frequency of play, etc. In some environments, individuals in the infant and juvenile age classes engaged in social play for approximately 1.5 to 3 hours a day. However, in one environment, not a single incidence of social play occurred during 261 hours of close range observation. The troops in which no play occurred were very cohesive (i.e., they seldom fragmented), and the animals traveled at close individual distances. Agonistic interactions were not uncontrolled. Copulations were observed; and 85 percent of the adult females were accompanied by infants, which indicates a normal rate of reproductive success for the species.Data are presented on friendly, aggressive, sexual, and spacing behavior in squirrel monkeys. These data indicate that (1) social play is not necessary for the development and/or learning of an adaptive modicum of social interaction patterns and troop cohesion, but (2) the opportunity to play provides learning experiences in which young animals can develop more complex, varied social interaction patterns and stronger habits for engaging in frequent social exchanges.