Eight-year study of social and ecological correlates of mortality among immature baboons of Mikumi National Park,Tanzania

The Cox Proportional Hazards Regression Model was used to examine ecological and sociodemographic correlates of mortality among 164 immature yellow baboons born over an 8-year period at Mikumi National Park, Tanzania. Ecological correlates were derived from seasonal rainfall. Mortality was lowest for immatures born during the late rainy season, when it was likely that nourishment for pregnant and lactating females was greatest. High mortality was associated with above-average rainfall early in the immature's first complete rainy season. This association may result from one or more of the following: exposure, increased ranging, or accelerated vegetation growth, each of which is thought to increase hazards for weanlings. When births for the 8 years of the study were pooled, a birth peak occurred during the early dry season. The larger number of births during a birth peak should intensify competition among mothers and among immatures. Mortality was greatest for immature females born during the season immediately following the birth peak, while lowest for immature females born during the season immediately preceding the peak. Immature female mortality was greatest when the troop size at birth was large, and was most severe for females born to low ranking mothers. The sociodemographic results are consistent with Wasser's hypothesis that cooperative attacks of female baboons upon other troop females suppress the others' reproduction and the vitality of their infants, thereby improving the relative competitive position of the attackers' own young.     

Co–Residence between Males and Their Mothers and Grandmothers Is More Frequent in Bonobos Than Chimpanzees

In long–lived social mammals such as primates, individuals can benefit from social bonds with close kin, including their mothers. In the patrilocal chimpanzee (Pan troglodytes spp.) and bonobo (Pan paniscus), sexually mature males reside and reproduce in their natal groups and can retain post-dependency bonds with their mothers, while immatures of both sexes might also have their paternal grandmothers available. However, quantitative information on the proportion of males and immatures that co-reside with both types of these close female relatives is limited for both species. Combining genetic parentage determination and group composition data from five communities of wild chimpanzees and three communities of wild bonobos, we estimated the frequency of co-residence between (1) mature males and their mothers, and (2) immature males and females and their paternal grandmothers. We found that adult males resided twice as frequently with their mothers in bonobos than in chimpanzees, and that immature bonobos were three times more likely to possess a living paternal grandmother than were immature chimpanzees. Patterns of female and male survivorship from studbook records of captive individuals of both species suggest that mature bonobo females survive longer than their chimpanzee counterparts, possibly contributing to the differences observed in mother–son and grandmother–immature co-residency levels. Taking into account reports of bonobo mothers supporting their sons'' mating efforts and females sharing food with immatures other than their own offspring, our findings suggest that life history traits may facilitate maternal and grandmaternal support more in bonobos than in chimpanzees.     

Development of co-feeding relationships in immature free-ranging Japanese monkeys (Macaca fuscata fuscata)

The co-feeding relationships of immature Japanese monkeys in the provisioned situation were studied. The most frequent co-feeders for immature females were diversified as compared to those for immature males. The number of immature females who showed strong co-feeding relationships with their mothers gradually decreased with age in both high- and middle/low-ranking matrilines, but the percent decrease was greater for middle/low-ranking immatures. Almost all immature females who displayed strong co-feeding relationships with adult males were from middle/low-ranking matrilines. Strong co-feeding relationships with mothers among immature males from high-ranking matrilines remained until 4 years of age. In contrast, strong co-feeding relationships with mothers among middle/low-ranking immature males decreased rapidly in the first year of life, and most 1- to 4-year-olds showed no strong co-feeding relationships with other group members. It is considered that middle/low-ranking mothers may not provide their immatures with a secure base for obtaining food in the provisioned situation.     

Immature wild orangutans acquire relevant ecological knowledge through sex-specific attentional biases during social learning

As a part of growing up, immature orangutans must acquire vast repertoires of skills and knowledge, a process that takes several years of observational social learning and subsequent practice. Adult female and male orangutans show behavioral differences including sex-specific foraging patterns and male-biased dispersal. We investigated how these differing life trajectories affect social interest and emerging ecological knowledge in immatures. We analyzed 15 years of detailed observational data on social learning, associations, and diet repertoires of 50 immatures (16 females and 34 males), from 2 orangutan populations. Specific to the feeding context, we found sex differences in the development of social interest: Throughout the dependency period, immature females direct most of their social attention at their mothers, whereas immature males show an increasing attentional preference for individuals other than their mothers. When attending to non-mother individuals, males show a significant bias toward immigrant individuals and a trend for a bias toward adult males. In contrast, females preferentially attend to neighboring residents. Accordingly, by the end of the dependency period, immature females show a larger dietary overlap with their mothers than do immature males. These results suggest that immature orangutans show attentional biases through which they learn from individuals with the most relevant ecological knowledge. Diversifying their skills and knowledge likely helps males when they move to a new area. In sum, our findings underline the importance of fine-grained social inputs for the acquisition of ecological knowledge and skills in orangutans and likely in other apes as well.

To understand the development and evolution of cognition of our closest relatives, we need to investigate their learning behavior during every-day life. This study finds that wild orangutan males and females differ in their social learning strategies and subsequent learning outcomes from an early age, underlining the general importance of, and the effects of sex on, social learning in non-human great apes.     

基于团抱行为的太行山猕猴社会联属

社会联属是指一些社会性动物社群内由于不同年龄、性别组的个体的社会角色与等级地位存在明显差异,在个体间形成的复杂的支配-从属关系,而这种支配-从属关系在不同的物种有着各自独特的模式(Clutton-Brock,1974)。了解社群内个体通过亲缘、非亲缘联盟、婚配、竞争而建立的支配-从属关系,是进一步开展社群内个体等级与资源竞争、互惠利益、母系投入策略等诸多研究的前提,     

Behavioral rhythms in the Nilgiri langur,Presbytis johnii

Eighteen complete daily profiles of 16 behaviors were compiled for three troops of Nilgiri langurs from Periyar Sanctuary in South India. Daily behavioral peaks from these profiles were tested for their associations with each other. Daily rhythms of feeding and resting showed four to eight peaks per day. When all observation days were lumped, however, a bimodal curve resulted as noted by most authors who have studied activity rhythms. The major daily behavioral associations were as follows: (1) feeding occurred during high rates of movement although not during major movement periods; (2) measures of troop movement were interrelated and occurred when troop members were dispersed; (3) movement was related to such active behaviors as whooping displays, coughing, juvenile whining, urinating, and scratching; (4) the above active behaviors showed some positive associations with each other; (5) play, grooming, and scratching showed positive associations with each other; and (6) rest periods were primarily periods of close social contact when grooming occurred and juveniles were with their mothers.     

The Huh Vocalization of White-faced Capuchins: a Spacing Call Disguised as a Food Call?

White-faced capuchins, (thus capuchins, predictably emit huh vocalizations at high rates within dense fruit patches. We sought to determine why white-faced capuchins at the La Selva Biological Station, Costa Rica produce these food-associated calls. Here we analyze the contexts in which this intra-group vocalization was emitted, including the spatial responses elicited from other troop members. A cumulative 26.6 h of continuous focal samples and 3314 spectrograms (including 1643 huhs) were analyzed from a study troop with 16 focal subjects. The mean individual rate of huhs was greater (1) during foraging versus nonforaging activities; (2) during fruit foraging compared to both visual searching for foraging sites and foraging for arthropod prey; and (3) when the nearest neighbor was within a 10 m radius of the focal animal compared to when the nearest neighbor was at greater distances. A huh also predicted a significant increase in nearest-neighbour distance; on average, mean nearest-neighbor distance increased 3 m within 2 min following a huh vocalization. Null models of change in mean nearest-neighbor distance over time were generated from the original data set by treating predetermined time points (140 s intervals) in the focal recordings as if those points marked instances at which huhs were produced by the focal subject. No significant alterations in nearest-neighbor distance were detected within time lags up to 100 s in these null models, supporting the conclusion that huhs are causally linked with subsequent increases in nearest-neighbor distances. Huhs were most evident when capuchins were within dense fruit patches, but these calls were produced across all foraging contexts. Our results suggest that huhs may not be food calls in the usual sense (i.e. informing others of the location of food sources to be shared), but may be more appropriately described as spacing calls. Huhs probably act to increase foraging efficiency by reducing overlap in foraging areas with other troop members.     

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.     

Reactions to fear as a proximate factor in the sociospatial organization of baboon progressions

The objective of this study was to test the hypothesis that fearfulness is a key proximate factor determining the nonrandom order repeatedly reported for baboon troops progressing from one location to another. According to this hypothesis, the most vulnerable troop members, the walking immatures, are expected in most circumstances to be cautious and to keep others between themselves and potential danger. The more confident adults, especially large powerful males, should tend toward the front and rear of progressing troops. The fear hypothesis predicts that in progressions toward a fear source, adult males should be near the front of the troop; on the other hand, when the troop is retreating from a frightening or tense situation, adult males should be found more toward the rear. Progressions of chacma baboons away from the location of a severe fright or in retreat from another troop were compared with other progressions. Adult males tended to be more rearward in these situations. The number of adults of either sex interposed between a fear source and the first walking immature was greater for retreating troops than for others. Some adult males continued to be near the front of the troop when retreating from tense situations.     

Intra-troop affiliative relationships of females with newborn infants in wild ring-tailed lemurs (Lemur catta)

To determine how the birth and development of infants influence their mothers' social relationships with other adult troop members, we observed two free-ranging troops of ring-tailed lemurs (Lemur catta) at the Berenty Reserve, Madagascar. The number of acts of affiliative contact that the mothers received from other adult troop members during the first and second months of infant life were significantly higher than those before they gave birth, and the values during the third month were as low as that before giving birth. Two mothers received acts of affiliative contact less frequently after their infants died, compared with the values while the infants were alive. On the other hand, more than 95% of all acts of licking of infants by adult troop members other than their mothers occurred when the infants were in contact with their mothers. These findings suggest that infants per se and mothers per se were not attractive, but rather the mother-infant pair was attractive to other troop members. Acts of infant-licking were observed in almost all mother-mother pairs and mother-non-mother adult female pairs, and in two thirds of mother-adult male pairs. Moreover, the frequency of infant-licking was not affected by female parity, female and male dominance rank, or infant sex. Therefore, acts of infant-licking, which are widespread among troop members, may function to make or maintain stable social relationships.     

Development of behaviors in a male spectacled langur (Presbytis obscurus)

An infant langur,Presbytis obscurus, was observed in a group setting, from birth until 1 year of age. Frequency or duration of 30 behaviors was recorded during 2 hour periods and plotted chronologically. Based on fluctuations and interrelations of these behaviors, age classes were designated. The Maternal Care Period (0–20 days) is characterized by close mother-infant contact, including a great deal of nipple contact and a high frequency of maternal behaviors. The Individuation Period (21–70 days) is typified by maternal restraint and retrieval, and independence and self-oriented behaviors like scratching, mouthing, and locomotory skills. The Socialization Period (71–240 days) is manifested by behavioral fluctuations, involving nipple contact, play, and care by other troop members and coincides with the molt from infant to juvenile pelage. Finally, during the Juvenile Period, the motherinfant distance increases and the mother interacts more with other troop members. Behavioral fluctuations observed in this infant langur are discussed with reference to other primates studied.     

Preliminary study of mother–offspring conflict in black and gold howler monkeys (<Emphasis Type="Italic">Alouatta caraya</Emphasis>)

Parent–offspring conflict has been scarcely studied in Neotropical primates. In this study, we explored mother–offspring conflict in a group of wild black and gold howler monkeys (Alouatta caraya) in northeastern Argentina. We used the all-occurrences technique to record behaviors, completing 712 h of observation. The results showed that all immature individuals between 2 and 23 months expressed conflict with regard to suckling or traveling with their mothers. Successful suckling attempts negatively correlated with the age of the immatures, occurring least frequently with the presence of newborns. In the juvenile period, the decline in successful attempts was a consequence of juveniles reducing suckling attempts and mother rejection.     

Establishment of a free-ranging colony of stumptail macaques (Macaca arctoides): Social relations I

Data on the social behaviour of a free-ranging troop of Stumptail macaques are reported for a period starting of August 15th to November 7th of 1974. Positive interactions take a greater part in the daily life of the troop than negative interactions. Individuals order themselves in an essentially linear dominance hierarchy and offspring rank immediately below their mother. Agonism and displacement are good predictors of dominance rank. Dominant individuals are a strong source of attraction for subordinates and the alpha male is a powerful social magnet for immatures. Grooming was found to be correlated with dominance rank and individuals holding adjacent ranks tend to interact positively with one another. To gain access to dominant females, subordinates direct a great deal of positive behaviour to the female’s youngest offspring. As social distance decreases the selection of a social partner becomes more strict and tends toward adjacency. However, factors such as motherhood, genealogical ties, and special relationships with non adjacent individuals, can override the tendency. The direction and quantity of male-care displayed by the adult male and by juvenile males toward younger individuals was found to be influenced by the troop’s dominance patterns. Sex differences were found to exist in male-care received and a negative association was found with the age of the receiver. Adult females are the main regulators of social relations and their rank and friendships provide their offspring with the social format, before puberty, in which they develop socially. The alpha male is the group protector, the performer of policing, an important element in the immatures’ social development, and a powerful source of attraction for all troop members.     

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.     

The play partners of immature baboons

In a troop of free-ranging baboons, infants played predominantly with each other, and played most with the infant of the highest-ranking female in their mothers' subgroup. The frequency of infant play appeared to be affected both by age and by the number and ages of other infants in the troop. Juveniles and subadults played more with their siblings than with other animals of their siblings' age. Juvenile and subadult females played primarily with infants, and played most with infants whose mothers ranked higher than their own. Juvenile and subadult males played most with like-sexed peers. The distribution of play partners among immatures illustrates how demographic and maturational factors, as well as those related to kinship, may reinforce or counteract one another during development.     

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.     

Changes in behaviour associated with pair formation in the polychaete Harmothoë imbricata (L.)

Spacing between individuals in populations of Harmothoë imbricata has been investigated both on the shore and in the laboratory. Males tend to occur closer together than females, and the mean male‐male individual distance measured was less than the mean distance between females; male—female distances for immature worms were intermediate. When worms mature they pair: the male mounts the female and lies across her dorsal surface. There is evidence that after spawning the members of a pair separate. Contact responses between worms have been investigated in the laboratory. Most encounters between immature worms lead to separation, as a result of one or both worms moving rapidly away from the other or fighting; females show more marked avoidance behaviour than males. The majority of male‐male and female‐female encounters between mature worms also lead to separation but in male‐female encounters the male usually mounts the female. A male which has mounted a female becomes highly aggressive and will attack intruding males but not females.     

Daytime deliveries observed for the ring-tailed lemurs of the berenty reserve, Madagascar

In the Berenty Reserve, Southern Madagascar, of the 16 deliveries recorded for ring-tailed lemurs from 1995 and 1997, 10 cases occurred during daytime hours (07:00 – 16:59). Four mothers lost contact with their troop members during parturition, but were able to rejoin them after about one hour. No attack from the individuals of the neighboring groups or predators on the mothers or their newborn infants was observed, whereas, other females of the mother’s own troop attacked them after delivery in two cases. Such daytime delivery may have originated from the circadian rhythm of the species’ nocturnal ancestors, who might have given birth during the daytime. This pattern may now be a non-adaptive feature, in agreement with the “evolutionary disequilibrium hypothesis (EVDH).”     

Responses of foster-mothers and troop members to adopted newborns in a captive group of rhesus monkeys

Two rhesus monkey males and two females, born to females caged singly, were exchanged with same-sex infants born to females in a large troop which was held in an enclosure in a different building. The ages of the infants were between 24 and 120 hr. The selected foster mothers (FMs) immediately accepted the foreign infants, allowed them to suckle and treated them as their own offspring. Compared with interactions with previous offspring, the FMs initially tended to be more possessive and restrictive of their foster infants: generally they took longer before they allowed the infants to sit at a distance from them and more readily retrieved them. The foster infants tended to be more active (‘fidgety’) than natural (control) offspring born to the troop. Non-related members of the troop, differentiated between foster and control groups. These troop animals more frequently approached and sat in proximity, often in fur-contact with, touched, groomed, and lipsmacked to, foster infants than control infants. The attractiveness of the fostered infants seemed to be slightly associated with the FMs' dominance rank. The foster infants were therefore viewed by others as having assumed the role afforded by the FMs' rank. Thus both FMs and other troop members recognized the unfamiliarity and novelty of the foster infant but the infants were still accepted into the group. We suggest that the different treatment of the foster infants by the troop may have consequences on the infants' future social development.     

Food transfers in immature wild western lowland gorillas (Gorilla gorilla gorilla)

The transfer of food items between individuals has been described in primates as serving an informative purpose in addition to supplementing the diet of immature individuals. This behaviour has yet to be described in western lowland gorillas (Gorilla gorilla gorilla), and results are presented here of observations of food transfers in immature gorillas at Mbeli Bai, Republic of Congo. The frequency of food transfers decreased with increasing immature age, while the frequency of independent feeding and processing of food increased. Transfers between mothers and infants were the most frequent, with infants attempting to take items from the mother. These attempts were not always successful and the item was relinquished on less than 50% of attempts. Mothers also took items from their offspring. The results point to the functional significance of food transfers in western lowland gorillas being informational. In a bai environment, where one species forms the majority of a visiting gorilla’s diet despite other species being available, the initiation of food transfers by immatures is proposed to serve the purpose of familiarising them with which species, and which parts of those species, may be eaten.