Adoption of an additional infant by a Western lowland gorilla (Gorilla gorilla gorilla).

A 10-year-old Western lowland gorilla, already caring for her own 14-month-old son, adopted a female neonate. The infant's mother (aged 7 years, 4 months) showed no interest in the infant, and it is unclear whether she abandoned the infant or whether it was seized by the dominant foster-mother. The foster-mother gave more maternal attention to the adoptee than to her own son but gave both infants the same protection. She adjusted her forms of transport to the age of each infant. The subadult mother of the neonate did not seek contact with her offspring during the first 4 weeks and in fact showed more interest in the 14-month-old male infant. Interactions between the two mothers were rare. The foster-mother's own male infant died 2 months after she had adopted the female infant. She looked after the adopted infant for 1 year, but then lost interest so that the adoptee had to be separated.     

Management of respiratory complications in a western lowland gorilla (Gorilla gorilla gorilla) born by cesarean section

A female western lowland gorilla (Gorilla gorilla gorilla) infant was delivered by cesarean section (C‐section) to an 18‐year‐old primiparous dam after prolonged labor. The infant required resuscitation at birth and was hospitalized for management of pneumonia and associated respiratory distress secondary to the aspiration of meconium‐stained amniotic fluid. The infant received nine days of intensive care with respiratory support, antibiotics, intravenous fluid therapy, anti‐inflammatory drugs, bronchodilators, and chest physiotherapy. Respiratory support included nasal continuous positive airway pressure (CPAP), and supplemental oxygen. Complications included right lung atelectasis secondary to bronchial obstruction and pneumonia. Following the resolution of pneumonia, visual reintroductions with the troop were initiated. The dam was given a medical lactation supplement (metoclopramide) and her mammary glands were stimulated to increase milk production. After several days of visual and olfactory introductions, the infant was successfully physically reintroduced to her dam at 12 days of age; the dam showed appropriate maternal response and nursing of the infant. The infant had appropriate growth and development, and 4 years later, has no evidence of negative side effects of neonatal respiratory disease. This is the first reported case of management of neonatal gorilla respiratory disease associated with a C‐section, with successful reintroduction to the family group after hospitalization.     

A case study of primiparous maternal and infant gorilla (Gorilla gorilla gorilla) behavior

A primiparous mother and her infant were subjects of a longitudinal behavioral study at Lincoln Park Zoo in Chicago, Illinois. From November 1998 to November 1999, we collected a total of 100 hr of focal nonhuman animal instantaneous point sampling and all occurrence data on the mother and her infant. After 8 months, we introduced the 4-member focal group to an 8-member gorilla group, thus providing an opportunity to study the effect of the introduction on mother-infant behavior. Overall, time the pair spent physically apart was notably high with contact and proximate scores steadily decreasing over time. The infant was largely responsible for maintaining social proximity, rarely leaving the mother and frequently approaching her. In contrast, the mother left the infant frequently and approached the infant minimally. Maternal affiliative and nonaffiliative behaviors fluctuated throughout the study. Over time, both decreased. Despite a precarious maternal relationship, infant developmental trends were typical for captive gorillas. The results of this study suggest that allowing flexibility in judging maternal conduct can be of benefit to successful gorilla husbandry.     

Social development during the first twenty weeks in the cotton-top tamarin (Saguinus o. oedipus)

Fourteen infant cotton-top tamarins from five captive family groups were studied during the first 20 weeks of life. We examined the roles of parents and of siblings of different ages as caregivers and as social companions for the infants, as well as the effects of group composition and group size on these roles. Parents and adult siblings played similar active roles in infant caregiving during the first few weeks after birth, with males showing a greater involvement than females. In groups without other offspring the two parents showed equal infant caregiving behaviour, whreas fathers carried more than mothers did in groups with offspring present. Although infants received more caregiving from males, they showed a preference for contact and proximity with their mothers. No sex differences were found in infant behaviour or in the direction of behaviour by caregivers toward infants. Twins showed greater amounts of both social and solitary play in weeks 15–20 than did singletons, and there was no effect of the number of older siblings on the amount of play shown by an infant.     

The Development of Play in the South American Fur Seal

Play behaviour in the juvenile South American fur seal (Arctocephalus australis) is described for the period of dependence on the mother (up to 32 months). Play does not appear to be a unitary category of behaviour, but may be separated into four distinct types: terrestrial social and solitary play and swimming social and solitary play. These four types show different development profiles, and appear to serve different functions. Terrestrial solitary play and the two swimming play forms appear to be juvenile specializations, the first to enable very young seals to gain motor skills rapidly in order to avoid dangers from conspecifics, the second two to enhance antipredator behaviour and foraging ability during the gradual transition to independence. In contrast, social play may be best thought of as gaining social skills necessary in adult life, prior to dispersal post-weaning. Juvenile fur seals which do not wean in their first year show an upsurge in social play which is not seen in the other play types. This upsurge coincides temporally with the peak of social play of the new cohort, and is presumably elicited by them.     

Deception and hiding in captive lowland gorillas (Gorilla gorilla gorilla)

Deception and hiding are described for a group of captive lowland gorillas comprising two adult males, one female, and her infant. The males repeatedly interacted with the infant, and their interest was repeatedly thwarted by the mother. As in other social situations in which one animal controls access to an object desired by another, deceit was used to thwart the other's control. Either one or both males at times concealed their actions toward the infant, inhibited their attention to the infant, created a neutral image to get the infant, or interacted with the infant to tease the mother.     

Mother-infant relations and infant development in captive chimpanzees and orang-utans

Four chimpanzee (Pan troglodytes)mother—infant dyads and four orangutan (Pongo pygmaeus)motherinfant dyads were studied for the first 11 months of the infants’ lives. For both species, ventroventral contact and nipple contact decreased over time at a similar rate, but total contact decreased earlier in the orangutans and was 50% lower than for the chimpanzees at the end of the study. Social play between the mothers and the infants did not differ in frequency between the species, but orangutans played above the ground and chimpanzees on the ground. Solitary play differed in form between the species and, like social play, reflected their differences in arboreal and terrestrial proclivities. In addition, the orangutans engaged in solitary play considerably more frequently than the chimpanzees during the second half-year of life. The developmental differences in mother-infant contact and solitary play of these apes are consistent with the differences in their speciestypical social organization. The data may reflect, therefore, early development of species differences in the social and relatively solitary natures of chimpanzees and orangutans, respectively. An erratum to this article is available at .     

A Case Study of Primiparous Maternal and Infant Gorilla (Gorilla gorilla gorilla) Behavior

A primiparous mother and her infant were subjects of a longitudinal behavioral study at Lincoln Park Zoo in Chicago, Illinois. From November 1998 to November 1999, we collected a total of 100 hr of focal nonhuman animal instantaneous point sampling and all occurrence data on the mother and her infant. After 8 months, we introduced the 4-member focal group to an 8-member gorilla group, thus providing an opportunity to study the effect of the introduction on mother-infant behavior. Overall, time the pair spent physically apart was notably high with contact and proximate scores steadily decreasing over time. The infant was largely responsible for maintaining social proximity, rarely leaving the mother and frequently approaching her. In contrast, the mother left the infant frequently and approached the infant minimally. Maternal affiliative and nonaffiliative behaviors fluctuated throughout the study. Over time, both decreased. Despite a precarious maternal relationship, infant developmental trends were typical for captive gorillas. The results of this study suggest that allowing flexibility in judging maternal conduct can be of benefit to successful gorilla husbandry.     

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.     

Social behavior of infant and mother Japanese Macaques (Macaca fuscata): Effects of kinship,partner sex,and infant sex

The behavioral interactions of 22 infant and mother Japanese macaques with other group members were studied. Focal-animal observations were made from the time of each infant’s birth until 1 year of age. Infants and mothers both displayed exceedingly strong preferences for associating with matrilineal kin and, specifically, for female kin. The degree of genetic relatedness was positively correlated with levels of spatial proximity, contact, grooming, aggression, and play. Overall frequencies of interactions with nonkin were very low, and partner sex was not an important factor in interactions with nonkin. There were no significant differences between male and female infants in interactions with kin versus nonkin. There was only one significant difference between male and female infants in interactions with males versus females: female infants showed stronger preferences for initiating proximity with females over males than did male infants. Because mothers provide the focal point for infant interactions during the first year of life, we compared the behavior of infants and mothers. Mothers were the recipients of more social interactions than were infants, mothers engaged in more grooming than did infants, and infants engaged in more social play than did mothers. These findings are only partially consistent with kin-selection theory, and the inadequacies of studying matrilineal kin discrimination to test kin selection are reviewed. The near-absence of infant sex differences in associations with social partners suggests that although maternal kin other than the mother are important to infant socialization, they probably do not contribute to the development of behavioral sex differences until after the first year of life.     

Behavioral development of a malformed infant in a free-ranging group of Japanese monkeys

The behavioral development of a malformed male infant in a free-ranging Japanese monkey group, whose hands were completely missing and whose hind feet were distorted, was investigated during the first one year of life, by comparison with normal infants. In the first few weeks of life, the malformed infant was not able to move by himself and was almost completely dependent on his mother's help. He gradually became able to creep with his forelimb elbows and distorted hind feet at about the first month of life, and was able to walk bipedally on his hind feet, though unstably, after the sixth month of life. His locomotor ability, however, was essentially inferior to that of normal infants throughout the first one year of life. His social interactions with the group members were different from those of normal infants. Normal infants increased their interactions with sameaged infants or older juveniles through active behavior-like play, whereas the malformed infant developed relations particularly with adults through behavior such as passive body contact. The conditions for survival of the observed malformed infant are discussed.     

Functions and social consequences of infant–adult male interaction in a captive group of lowland gorillas (Gorilla gorilla gorilla)

The functions and social consequences of infant-adult male interaction in a captive group of lowland gorillas were evaluated. The two males repeatedly attempted to interact with the infant, the infant sometimes attempted to interact with the males, and the mother usually interrupted interactions between male and infant. Infant-directed actions by the two males frequently showed their interest in the infant and infrequently showed care giving toward her; their other infant-directed actions occurred near the time of excitement or of playful actions between adults. Male-directed actions by the infant frequently showed its interest in one male and infrequently showed care seeking from him. All infant-adult male interactions but one occurred in the less stimulating of the gorillas' two enclosures. Boredom and the mother's frequent thwarting of contact between a male and infant are suggested as influences on the males' interest in the infant. The data suggest that availability of interesting objects alleviated the boredom of captivity for males and thus dissuaded them from seeking stimulation which sometimes resulted in harmful behaviors toward the infant.     

Sex differences in play among western lowland gorilla (Gorilla gorilla gorilla) infants: implications for adult behavior and social structure

Mammalian play is believed to improve motor skills as well as facilitate the development of social relationships. Given the marked sexual dimorphism in gorilla body size and the role assumed by the male in protecting the group from conspecifics and predators, the motor-training hypothesis of play predicts that male infants should exhibit higher frequencies of social play than female infants, and that males should prefer to play with other males. Given that adult female gorillas are strongly attracted to adult breeding males and form only weak social bonds with unrelated adult females, the social-relationship hypothesis of play predicts that female infants should prefer to play with males. These hypotheses were tested in a 22-month study of 12 gorilla infants, aged between 0-5 years, living in three zoological parks in Chicago and Atlanta. Consistent with the hypotheses, male infants played more than female infants did, and both male and female infants preferred to play with males rather than with females. These findings suggest that sex differences in play in the great apes and other primates can be predicted by the characteristics of adult behavior and social structure above and beyond the patterns of sex-biased dispersal or coalition formation with same-sex kin.     

Behavioral changes of a juvenile gorilla after a transfer to a more naturalistic environment

Play behavior and stress-associated behavior of a captive juvenile gorilla were observed before and after his transfer to a larger and more natural environment. The gorilla was observed for 4 months after the transfer and at 1 and 4 years after the transfer. Throughout his first month in the new environment play decreased dramatically. Although play subsequently increased again 2 months and 1 year after the transfer, it never reached the levels of play in the old environment. Four years after the move his play had decreased again to the low level of his first month in the new environment. Two of his stress-associated behaviors, coprophagy and regurgitation/reingestion, decreased after the transfer. Self-clasping behavior increased initially in the new environment and remained at high levels 1 year after the move. Four years after the move his self-clasping behavior was significantly less than at 1 year after the move; however, it continued to be significantly greater than in the old environment. These findings suggest that larger and more natural environments do not necessarily result in more play activity or a reduction in all stress-associated behavior.     

Sex differences in the behaviour of immature captive lowland gorillas

Studies of the behaviour of 26 (12 males and 14 females) captive infant and juvenile lowland gorillas showed clear sex differences. Females showed greater interest in young infants and were more active in nest building as well as in solitary and social grooming. Males were more active in locomotive, dominance, and aggressive behaviour and in social play. Hand-rearing further increased aggression. Males were more aggressive when they lived with only one partner, and they rose in rank even above older females, a pattern that has not been observed in naturally reared gorillas.     

Behavioral responses of an infant gorilla to maternal separation in a captive social group of lowland gorillas (Gorilla gorilla gorilla)

The present report describes behavioral reactions of a 33-month-old female infant gorilla to maternal separation in a captive social group whose composition is similar to that of wild groups. The infant gorilla responded differently to two types of maternal separation. When she remained alone for a few hours, she cried repeatedly and moved restlessly, indicating protest. Upon reunion and also for a few days thereafter, an intensification of the mother-infant relationship occurred. On the other hand, when she was separated from her mother but remained with the other group members for nine days, she did not display any behaviors that could be characterized as protest, but rather showed clear behavioral depression. During the 9-day separation period, she hardly played with other group members but she developed affiliative relationships with the leading male. After the reunion from the 9-day separation, she spent as much time near her mother as before separation and played with other infants at a level similar to that before separation, while she sometimes displayed behavioral patterns demanding the maintenance of physical contact with her mother. The present findings are compared with other reports in great apes and human children.     

The ontogeny of social play in a feral troop of vervet monkeys (Cercopithecus aethiops sabaeus): The function of early play

We describe the ontogeny of social play over the first 30 weeks of age in a troop of feral vervet monkeys (Cercopithecus aethiops sabaeus) in Barbados. Play time increased rapidly for the first 10 weeks but remained relatively constant thereafter. The form of play changed with infant age; bouts became more frequent but of shorter duration. Play time, bout frequency, and bout duration at a given age differed between infants; younger infants altered their play patterns to complement those of older infants. All infants played more within their own year class than with older juveniles; play time increased with decreasing age difference between the infant and the play partner. Infants terminated a higher proportion of their play bouts the greater the age difference between themselves and their play partners. Preferred play partners are therefore individuals of similar age that will be similar in size and have matched motivation to play and form of play. Neither play time nor proportion of bouts initiated or terminated was correlated with the social rank of the play partner, which suggests that play is not directed toward individuals that may be high-value alliance partners. Maternal intervention in play occurred primarily when infants were<10 weeks old. It was not correlated with the age or social rank of the mother or with the age or social rank of her infant's play partner. Infants played more and terminated a lower proportion of their play bouts in the absence of their mothers than in their presence. Our results are consistent with the hypothesis that the primary function of early play is to enhance physical fitness and to develop coordination and other fighting skills, with minimal risk of injury.     

Play behaviour and its effects on social development of common chimpanzees (Pan troglodytes)

The aim of the study was to monitor the social development of infant and juvenile common chimpanzees (Pan troglodytes) through their play behaviour at Taronga Zoo in Sydney in order to examine the possible effects of captivity (such as limited opportunities to play) on social development. Play behaviour was observed by focal animal sampling to determine individual differences, and their relationship to age, sex, and relatedness of the subjects. Analysis revealed marked individual variations in social, solitary, and object play behaviours indicative of a relatively well-balanced social and physical environment. Subjects showed a marked preference for play-partners of a different age compared to their own, and initiated interactions with similar frequency with members of both sexes. Many social-play dyads consisted of related individuals, and familiarity with prospective play-mates was the most decisive factor in social interactions.     

Long‐term proximity relationships in a captive social group of western lowland gorillas (Gorilla gorilla gorilla)

To visualize long‐term social relationships among 12 gorillas in a captive breeding group at the San Diego Wild Animal Park, San Diego, CA, the multidimensional scaling (MDS) procedure was applied to proximity (within 5 m) values collected in five different periods over 2.5 years. The resulting two‐dimensional representations clearly show that in samples taken during this 2.5‐year period, the silverback male was surrounded by five adult females, while three infant or young juvenile females, gathered in a body, remained between the silverback male and adult females. Some adult females maintained proximity to the silverback male more frequently than other adult females throughout the five periods. Unlike mountain gorillas in the wild, females with dependent offspring did not tend to stay near the silverback male more frequently than other females, and related females did not tend to spend more time near each other than non‐related females. Three older juvenile or young adult males were plotted the furthest from the silverback male, with gradual changes with increasing age. The usefulness of the MDS procedure, which can be used to visualize easily and clearly the social relationships among individuals, is discussed from the viewpoint of the management of breeding groups of captive gorillas. Zoo Biol 20:197–209, 2001. © 2001 Wiley‐Liss, Inc.     

A preliminary behavioral comparison of two captive all-male gorilla groups

Gorillas live in polygamous harem groups, generally composed of one male, several adult females, and their offspring. With an equal numbers of male and female gorillas born in captivity, however, housing gorillas in social breeding units inevitably means that some males will not have access to female social partners. Thus, the future of the captive gorilla population depends on the collective ability of zoos to house equal numbers of males and females. This study examined the behavioral profiles of two all-male groups of captive lowland gorillas (Gorilla gorilla gorilla) to provide information on this type of housing situation. One group consisted of three subadult individuals, while the other consisted of two subadults and a silverback. Data were collected during two 6-month intervals, for a total of 284 hr. The behavioral profiles of the animals were stable over the course of the study but proximity patterns changed. Differences in feeding, solitary play, and object-directed behavior were found between groups, while no significant differences were observed in affiliative or agonistic social behavior. At both institutions, group cohesion appeared to be high, particularly between subadults; these individuals spent approximately 10% of their time engaging in social behavior and 25-50% of their time in close proximity (within 5 m). However, the Zoo Atlanta males spent significantly more time within 1 m and 5 m of each other than the Santa Barbara males, which may reflect a higher level of cohesiveness among members of the Zoo Atlanta group. The behavioral profiles of the animals in this study were similar to those found in bachelor groups of wild mountain gorillas. One notable exception was the absence of homosexual behavior between the silverback and subadults in Santa Barbara and the low frequency of this behavior between subadults in both groups. Although more longitudinal data are needed, these data suggest that all-male groups can be a feasible housing strategy for males at certain periods of their life span. Zoo Biol 20:27-40, 2001. Copyright 2001 Wiley-Liss, Inc.