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.     

Adoption of infant orphan chacma baboons

During a study of chacma baboons, Papio ursinus, in the Moremi Wildlife Reserve, Botswana, the mothers of 10 infants disappeared. Pre-reproductive males and females, all 4 to 5 years old, adopted nine natural orphans, and one older orphan was not adopted. Compared with other troop members, 4- and 5-year-old caregivers would incur the lowest costs of adoption in terms of interference with their direct reproductive potential. In the five instances in which relatedness of natural orphans could be assessed, caregivers were probably close relatives of orphans they cared for. By comparison, 5-year-old males immediately adopted two experimentally introduced orphans.     

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.     

Deaths in a desert baboon troop

Over a 4-year period, three of 22 infants born in a desert-dwelling chacma baboon troop (Papio ursinus) survived to more than 6 months of age. Tick infestation and infant kidnapping by adult females were the main causes of infant death. The high neonatal mortality resulted in a rapid birth rate through a decrease in duration of interbirth intervals for mature females. There were more adult male deaths in the troop than adult female deaths. Males died from canine inflicted wounds sustained during fights.     

Grooming relationships of adolescent orphans in a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama: a comparison among orphans with sisters, orphans without sisters, and females with a surviving mother

The present study examined grooming relationships of adolescent females in a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama. To assess whether the loss of the mother influenced the grooming relationships of adolescent females (5–7 years old), we compared the time spent in grooming interactions and the number of grooming partners among the following three groups: 6 adolescent orphans with sisters, 9 adolescent orphans without sisters, and 11 adolescent non-orphans with surviving mothers. In Japanese macaques, grooming most frequently occurs between mothers and their daughters. Therefore, it is expected that if the mother is lost, orphans will devote less time to grooming interactions than non-orphans. However, the time spent in overall grooming interactions did not differ among the three groups. While non-orphans maintained grooming relationships with their mothers, orphans acquired alternative grooming relationships with other group members. Orphans adopted two kinds of tactics to compensate for the loss of the mother. First, adolescent orphans with sisters developed more affiliative grooming relationships with their sisters than non-orphans with sisters. Secondly, adolescent orphans without sisters spent more time in grooming interactions with same-aged females and non-related adult females. Moreover, regarding grooming interactions with same-aged females and non-related adult females, orphans without sisters had a larger number of grooming partners than non-orphans. These results indicate that adolescent females have enough flexibility to develop their grooming network after the loss of their mothers, and that the lack of mother and sisters might accelerate socialization of adolescent females and enable them to be integrated in reciprocal adult grooming relationships.     

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.     

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.     

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.     

Troop Extinction and Female Fusion in Wild Japanese Macaques in Yakushima

We observed three cases of troop extinction and two cases of female fusion in the wild population of Japanese macaques on Yakushima Island, Japan. Troops P and T decreased in size relatively slowly over a few years until each troop consisted of only three monkeys. Several months later, the remaining adult female of P merged with the adjacent troop S, followed by the remaining female of T. S subsequently also decreased in size and disappeared about 2 years later. In the early stage of troop decline, the mortality rate of adult females was as low as in a growing troop, but the birthrate was quite low. In the late stage of troop decline, the mortality rate increased and the birthrate remained low. An important factor leading to troop extinction may be an increase in population density and the resulting increase in intergroup competition. During the period when P and T declined and ceased to exist, the range of the adopted troop shifted to cover their previous ranges. In the fused troop, there was no severe aggression directed towards the immigrant females or harassment from residents of the adopted troop and there was affiliative social interaction between the immigrant females and resident members. These results agree with previous reports on female fusion: it occurs when the shrinking group consists of one or no adult member, and the immigrant females are not at a severe disadvantage in their adoptive group. A possible benefit for immigrant females is to avoid disadvantage of one-adult group in conflict with conspecifics. A possible cost for immigrant females is transfer to the other troop or to unfamiliar area or both. The cost to transfer to another group may not be high because the members of the adoptive troop are relatively tolerant to immigrants. The cost to transfer to unfamiliar range may be minimized by immigration to the troop whose range shifted to the immigrants' former range.     

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.     

Influence of artificial food supply on population parameters and dispersal in the Hakone T troop of Japanese macaques

A free-ranging troop of Japanese monkeys was observed for seven years from April 1971 to March 1978 in the Hakone area, Kanagawa Prefecture, Japan. This troop was fed artificially between 1956 and 1977. The artificial food supply was reduced by about half after 1974. The troop-size fluctuated around 100 between 1971 and 1974, but fell drastically from 91 in 1975 to 58 in 1978. Population parameters were compared between the two periods of 1971–1974 and 1975–1977. Clear differences between the two periods were found in primiparous age, ratio of non-natal resident males to all resident males, ratio of newcomers to non-natal resident males, age-specific disappearance rate, and proportion of deserters observed in the study area. A correlation existed between the number of males and females of 5 or more years of age in the troop. The numbers in the three age-sex groups (natal males, non-natal males, and females of 5 or more years of age in the troop) were closely connected with one another. The scarcity of food supply may have caused not only males but also females to disperse. The drastic decrease in troop-size after 1974 could be based on the disappearance of adult females. The cause of the dispersal of young males and adult females could have been mutual competition among the troop members for food, and that in adult males could have been competition for females.     

Vervet monkey grandmothers: Interactions with infant grandoffspring

Social relationships of 30 infants with their maternal grandmothers were studied in a captive colony of vervet monkeys (Cercopithecus aethiops sabaeus).Grandmothers and grandinfants formed affiliative relationships with one another that could be distinguished from the infant’s relationships with nonkin adult females and with other adult female kin. The intensity of the grandmother—grandinfant relationship varied according to several factors which were related to the infant’s vulnerability to mortality and to the grandmother’s ability to provide effective social support. High-ranking grandmothers spent more time near their grandinfants, and initiated more grooming and caretaking of their grandinfants, than did lower-ranking grandmothers. Grandmothers spent more time near their daughter’s first surviving infant than near later-born infants, and when grandmothers had more than one adult daughter, they spent more time near the infant of the younger daughter. These results, combined with the fact that the presence of a maternal grandmother has been associated with a reduction in the rate of infant mortality in this colony (Fairbanks and McGuire, 1986), suggest that grandmothers are actively contributing to the reproductive success of their adult daughters and to the survival of their infant grandoffspring.     

Plasma cholesterol levels in free-ranging macaques compared with captive macaques and humans

Plasma total cholesterol in free-ranging Japanese macaques (Macaca fuscata) on Koshima islet and in free-ranging long-tailed macaques (Macaca fascicularis) at Pangandaran in Indonesia was found to occur at very low levels compared with captive macaques and humans. Although total cholesterol levels in captive macaques were lower than humans, differences in HDL cholesterol levels were only small. In both sexes of wild and captive Japanese macaques, total cholesterol levels decreased from birth through to young adulthood but then increased in adult females of the captive group. In contrast, the value for adult females of the wild troop remained at a low level. Low TCH levels in adult females of the wild Japanese macaque troop may be due to a low energy intake and may have caused a delay in the onset of sexual maturation. Plasma TCH levels increased with the addition of 0.1% dietary cholesterol over six weeks in captive long-tailed macaques. That the cholesterol value after six weeks was dependent on cholesterol levels prior to supplementation indicates that captive macaques are slightly saturated with cholesterol.     

The behavior of white-faced capuchins (Cebus capucinus) at a dry-season waterhole

During a study of white-faced capuchins (Cebus capucinus) in Santa Rosa National Park, northwest Costa Rica, the study troop drank daily from a single terrestrial waterhole for approximately three months during the dry season. The drinking order of troop members at the waterhole was not random: adult males tended to be in the first quartile of the drinking progression, adult females generally occurred with equal frequency throughout the progression, and juveniles drank most commonly in the third quartile. There were also differences in the usual drinking ranks among individuals of the same age-sex class. It is hypothesized that those adult males which are usually first in the progression are increasing their personal fitness by reducing the risk of predation on their offspring and on potential mates. The tendency of adult females to precede juveniles may similarly reflect protection of offspring. The daily visits to the waterhole by the study troop did not appear to greatly restrict the use of their range. It is suggested, however, that the availability of standing sources of water may be an important factor affecting the local distribution and density of capuchins in seasonally and chronically dry areas.     

Adoption in Anthropoid primates

Reports of adoption in nonhuman primates are reviewed, including spontaneous adoptions of orphans or infants whose mothers have been removed from the group, temporary adoptions of offspring of sick mothers, adoptions arising out of kidnapping, and adoptions resulting from manipulations involving presenting infants to adults. Adoptive behavioral patterns resemble nonadoptive alloparental patterns. The literature indicates certain trends: adult females, especially if lactating or in the late stages of pregnancy, are most likely to adopt neonates. Older infants are more likely to be adopted by juveniles or by adult males. Weaned or weanable orphans that get adopted have reasonable chances of survival, while orphans still reliant on milk are unlikely to survive. An infant adopted by an adult female will develop socially as a member of the female’s matriline. Adoptions involving closely related individuals are consistent with kin-selection theory. Others appear to reflect “reproductive error” arising out of an attraction to young infants. Yet other cases might reflect reciprocal altruism. Continued documentation of cases of adoption will yield more data on costs and benefits and on whether rates and forms of adoption, such as alloparental behavior, vary systematically with social systems.     

Demography of Lemur catta at Berenty Reserve,Madagascar: Effects of Troop Size,Habitat and Rainfall

We censused Lemur catta within a 1 km² study area at Berenty Reserve, Madagascar, during the September–October birth season for 19 years between 1963 and 2000, a total of 290 troop counts (266 with age and sex). The non-infant population was 155 in 1972–5, fell to 105 in 1985, and rose to a maximum of 282 in 1997, while troops increased from 12 in 1972–1985 up to 25 in 1998–2000. Local density varies between habitat types from 1 per ha to ca. 6 per ha. Troops fission at ca. 15–25 individuals, or 6–10 females. Adult sex ratio has no apparent correlation with fissions, birth rate or survival. Birth rate falls steeply with number of adult females, from 80–100% in 2-female troops to about 50% in 8–10 female troops. The penalty for large troop size is greater in the dense, rich areas, but nonetheless troops there are also larger. One-year-survival does not vary with troop size, and is lower in the sparse, dry zone. Troop size is too large for optimal birth rate, but fissioning to much lower size might make troops too small for optimal adult survival, given the intense intertroop competition. This reflects Sibley's (1983) conjecture that troop sizes may not reach stable optima. Rainfall per lemur-year (beginning Oct 1) varied from 265 to 894 mm. Drought followed by rain can eliminate >90% of a cohort, especially in the dryest zone. Possibly this results from fruit failure in years following drought. It is unknown whether food supplementation of some Berenty troops is dangerous for the forest, or helpful for an isolated and vulnerable ring-tailed lemur population.     

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.     

Troop fission in wild ring-tailed lemurs (Lemur catta) at Berenty, Madagascar

A detailed fission process in a wild ring-tailed lemur (Lemur catta) troop was observed at Berenty Reserve, Madagascar. The troop fission occurred as follows: 1) During the birth season in 2000, two adult females (mother and daughter) were evicted as a result of "targeted aggression" (i.e., intense and persistent aggressive behavior toward particular individuals). 2) Two adult and three immature females in the same kin group as the evicted females spontaneously immigrated into the new group. 3) A male immigrated into the new group 1.5 months later. 4) The new troop successfully established its own home range. This report exemplifies three characteristics of troop fission in ring-tailed lemurs. First, targeted aggression initiated the fission process. Second, the troop females divided along matrilineal lines. Finally, no male played a specific role in the fission process.     

Social relationships of nulliparous young adult females beyond the ordinary age of the first birth in a free-ranging troop of Japanese macaques (Macaca fuscata)

We describe the social relationships of young adult female Japanese macaques (Macaca fuscata) in a free-ranging troop in Arashiyama, Kyoto, Japan, who remained nulliparous beyond the ordinary age of first birth because of contraceptive administration. We observed 12 young nulliparous adult females (6–9 years old) for 270 h and 10 min from 2 February to 5 October 2010. The majority maintained close relationships with their mothers through proximity and grooming, whereas a few had very infrequent social interactions with their mothers. Most had asymmetrical grooming relationships; the grooming they received from unrelated adult females was less than the grooming they gave. Young adult females who had less frequent interactions with their mothers by either proximity or grooming received more grooming from a larger number of unrelated adult females than did those who had more frequent social interactions with their mothers. These results indicate that most young adult females who remained nulliparous beyond the ordinary age of first birth tended to maintain close relationships with their mothers, and their grooming relationships with unrelated adult females were inversely related to the degree of closeness with their mothers.     

Inter-male associations in a wild Japanese macaque troop on Yakushima Island,Japan

Adult male association and its annual change were studied in a wild population of Japanese macaques (Macaca fuscata yakui) on Yakushima Island, Japan. Unlike many other Japanese macaque troops, adult troop males frequently maintained proximity and exchanged grooming with one another in both the mating and non-mating seasons, and the dominance relationship rarely appeared in such inter-male associations. The few cases of agonistic interactions occurred mostly when estrous females or food resources were immediately concerned. Although troop males were very intolerant to newly appeared solitary males (new males) during the mating season, close associations were formed between troop males and new males as soon as the mating season terminated. The consort of new males and lower-ranking troop males with estrous females was frequently disturbed, but these males could copulate no less frequently than higher-ranking males. A comparison among macaque species suggests the existence of two forms of inter-male association: (1) the frequent association based on the symmetrical exchange of social behaviors; and (2) the infrequent and asymmetrical association related to the dominance relationship. The form of inter-male association seems to be influenced by whether or not males can keep close associations with females throughout the year.