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.     

Social behavior of a group of orangutans (Pongo pygmaeus) on an artificial island in Singapore Zoological Gardens

The behavior of 12 orangutans (three adult males, two adult females, two subadult males, three adolescent males, and two infant males) was observed on a 450-m² island at the Singapore Zoological Gardens (SZG). Male orangutans (6–18 years old) showed less social and solitary play as they aged; adults (over 16 years old) were not seen to play. As they grew older males increasingly spent less time making physical contact, but the amount of time they spent in proximity (within arm's length) to others increased. Adult females regularly played with other group members. Contact, allogrooming, and social play showed nonrandom relationships between individuals. Adult females showed the most allogrooming and contact, adolescent and subadult males the most play. There was no obvious dominance hierarchy. One adult male spent about 10% of his time walking around the perimeter of the island. One-year-old infants rarely interacted with other individuals apart from their own and the other infant's mother. While orangutans lead relatively solitary lives in nature, it was concluded that the opportunities for social contact and play provided by the SZG orangutan island were beneficial to this species in captivity. Opportunities for social interaction provided the animals with a means of increasing the stimulus component of their environment, thus compensating for the inevitable restriction of complexity and unpredictability as compared with the wild state.     

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.     

Changes in the rhesus mother-infant relationship through the first four months of life

Measurements of the course of interactions between rhesus monkey infants (Macaca mulatta) and their mothers during the infant's first 16 weeks showed changes in the tendencies of both partners to be together and apart. Referring only to the partner who was primarily responsible for an age-related change, by using a single index of responsibility for contact or proximity, was found to be an oversimplification. Maternal rejecting behaviour may have been primarily responsible for changes in the time spent apart only during the first 6 weeks. After the infants' sixth week, both partners' tendencies to be apart increased together. Infants then began to spend longer away partly to interact with social companions other than their mother. Mothers restricted and followed their infants more up to week 4, but after week 8 decreases in these measures allowed infants to spend longer away. Similarities between the time courses of the time spent apart from their mothers by rhesus infants in this study and in field studies are pointed out. The similarities seem striking partly because differences between studies that do not use confidence intervals (or standard errors) cannot be shown easily. Conflict between parent and infant occurred, but how it appears, and how significant it is in each species at each infant age, remains to be discovered.     

Mating season effects on mother-infant conflict in Japanese macaques,Macaca fuscata

The impact of seasonal mating on the mother-infant relationship during the first year of the infant's life was documented in a confined troop of Japanese macaques. During the weeks in which the mothers were being mounted, negative behaviour directed towards the infants increased. As maternal rejections and punishments escalated, the infants displayed regressive behaviour (showing signs of distress more frequently). Infants also groomed their mothers at an increased rate at this time. Behaviour that indicated increased independence did not show increases during this time. Moreover, behaviour negatively associated with independence, such as ventral contact and proximity to the mother, remained stable throughout this time period. The mother-infant relationship undergoes a period of conflict during the mating season not because the mother is weaning her infant, but because it is to her reproductive advantage to regulate the times in which the infant is allowed to suckle.     

Patterns of infant handling and relatedness in Barbary macaques (<Emphasis Type="Italic">Macaca sylvanus</Emphasis>) on Gibraltar

Among papionin primates, the Barbary macaque (Macaca sylvanus) shows the most extensive interactions between infants and group members other than the mother. Two different types of interactions occur: (1) long-lasting dyadic interactions between a handler and an infant, and (2) brief triadic interactions between two handlers involving an infant. Previous investigations showed that infant handling by males is best explained as use of infants to manage relationships with other males. In contrast, no adaptive explanation for infant handling by females emerged. Here, we compared the infant-handling pattern between subadult/adult males and subadult/adult females in a free-ranging group of 46 Barbary macaques on Gibraltar to test whether the relationship management hypothesis also applies to female handlers. We further investigated the infant-handling pattern of juveniles and used microsatellite markers to estimate relatedness between infant handlers and the infant’s mother. We found that males, females and juveniles all participated extensively in triadic interactions using infants of above-average related females. In contrast, only males and juveniles were highly involved in dyadic interactions with infants of related females, while females rarely handled infants other than their own. The pattern of infant handling was entirely compatible with the predictions of the relationship management hypothesis for males and mostly so for females. Moreover, our genetic analysis revealed that males and females differ in their partner choice: while females preferred to interact with related females, males had no significant preference to interact with related males. We further discuss the observed above-average relatedness values between infant handlers and the infant’s mother in the light of kin-selection theory.     

Group responses to parturition inMacaca arctoides

The birth of an infant to the highest ranking female in a captive social group of stumptail macaques (Macaca arctoides) is described. Along with certain details of delivery behavior, the responses of group members to the birth are given. The alpha male and two juvenile males were sexually aroused just prior to and during parturition. Adult females paid no special attention to the birth. A subadult nulliparous female and a young adult primiparous female showed interest in the eating of the placenta by the female. The new mother's juvenile son was the monkey closest to her for about two hours after the birth; approaches by other monkeys, especially adult males were avoided. Time of delivery, signs of labor, and the behavior of the mother are also included.     

Subadult male orangutan sociality and reproductive behavior at Tanjung Puting

During a four-year period at Tanjung Puting Reserve, Central Indonesian Borneo, subadult males were observed for 670.5 observation hours, 463 hours of which were as focal individuals. Subadult males were quite gregarious, participating in groupings for 40.9% of the time they were observed as targets. Subadult male sociality centered around females; 83% of the time subadult males spent in groupings was exclusively with females, as compared to 3% of contact time spent exclusively with other males. Much subadult male sociality can be understood in terms of male-male competition for females. Interactions between adult and subadult males were almost entirely determined by the presence or absence of females. Adult males were more belligerent when females were present. Twenty-two copulations or attempted copulations occurred during 16 subadult male-female encounters, two of which were consortships. The majority of subadult male copulations (86%) were resisted matings. Outside of consortship, resisted matings (or the first in a series of resisted matings or attempts) usually took place at encounter or shortly thereafter. Subadult males also surreptitiously followed adult males and their consorts. Subadults frequently located receptive females before adult males did but were replaced by adult males when these appeared. Subadult male reproductive strategy consisted of both sneak/“rape” and consort tactics with sneak/“rape” predominating.     

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.     

The social development of baboons in their first three months

The development of the mother-infant relationship is expressed in terms of the change in typical relative positions of the pair and in the pattern of contacting and leaving they showed.
Rainy periods increased the time the infant spent asleep with its mother, the effect being more than that produced by the infant's age on sleeping time in the first three months of life.
Rate of development of mother-infant relationships was compared with that of Rhesus monkeys in similar conditions, and found to be very closely comparable.
Interactions by infants with other baboons were found to be quantitatively and qualitatively different for each available demographic class (though some classes were only represented by a single individual). Results illustrated different rates of social maturing in the sexes, differential behaviour of the adult male towards the sexes of infants, and the existence of a special relationship between siblings.
Interactions of neoparturient mothers with other adults are characterized by high overall frequency, with a high frequency of avoiding of friendly approaches by the mother. Both these have returned to normal frequency levels in the third month.
Restriction of infants by mothers was seen only in the caged group. Its immediate effects on the behaviour of the infant and its association with other maternal social behaviour are described.     

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.     

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.     

Observations on infant sharing in captiveColobus polykomos

The behavior of two female and two maleColobus polykomos after the birth of a baby into a zoo exhibit was recorded and then analyzed. Infant sharing was observed between the mother and the subadult female. Initially transfers of the baby were traumatic, but as the day progressed the transfers became more amicable. The subadult female was not allowed to handle the baby while it was nursing and this was monitored, in large part, by one of the adult males. Although transfers were frequent between the two females, neither male was observed to hold the baby until it was four weeks old. There was a marked discrepancy in the ability of the females to handle the infant and this is discussed in light of some observations made on chimpanzee mothers in the wild.     

The birth of a wild mountain gorilla (Gorilla gorilla beringei)

The live birth of a wild mountain gorilla is described. Details of the birth process are given along with the mother’s periparturitional behaviour and the responses of others to the birth. The mother, a multiparous female, gave no observable indication that birth was imminent, and delivered her infant quickly and easily. During parturition, a subadult male showed interest in the proceedings. Following delivery, several animals approached the mother, who then left the birth site. The mother cleaned her infant and by two hours postpartum had established ventro-ventral contact and, possibly, nursing. These data are related to relevant observations from the literature and unpublished data on other animals from this study.     

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.     

Impact of male takeover on intra-unit sexual interactions and subsequent interbirth interval in wild Rhinopithecus roxellana

Data were collected on sexual interactions before and after a male takeover of a one-male unit (OMU) of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in the Qinling Mountains, China. The original unit consisted of an adult male, 2 adult and 2 subadult females, 2 female juveniles and a single infant. Following the takeover, the new resident male copulated with 1 adult female, which was not lactating. Subsequent to the disappearance of her infant, the second (lactating female) entered breeding condition and began to solicit copulation with the new resident male. The subadult females also engaged in matings with the new male. The new resident male was observed mating, on 3 occasions, with females in 2 other OMUs. These are the first observations of sexual behaviour in free-ranging Sichuan snub-nosed monkeys after an OMU takeover. Sexual interactions play an important role in establishing relationships between the new male and resident females in the OMU.     

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.     

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

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