Procedures for improving maternal behavior in captive chimpanzees

Captive female chimpanzees who have had no opportunity to observe mothers with infants or to interact with infants often show inappropriate maternal behavior, particularly with their first-born infant, and this usually results in the removal of the infant to be human-reared. The present study used two techniques to encourage appropriate maternal behavior in ten pregnant female chimpanzees. These females were housed together with unrelated infant chimpanzees to adopt, or with lactating female chimpanzees and infants to observe. In five cases both techniques were used, in two cases only the first technique was used, and in three cases only the second technique was used. All ten female chimpanzees showed appropriate maternal behavior when their infants were born, in contrast to a group of eight female chimpanzees who had no such experience whose infants had to be removed for human-rearing. It is suggested that these techniques, or adaptations of them, could be applied to many other captive female chimpanzees with similar results.     

Social learning of a communicative signal in captive chimpanzees

The acquisition of linguistic competency from more experienced social partners is a fundamental aspect of human language. However, there is little evidence that non-human primates learn to use their vocalizations from social partners. Captive chimpanzees (Pan troglodytes) produce idiosyncratic vocal signals that are used intentionally to capture the attention of a human experimenter. Interestingly, not all apes produce these sounds, and it is unclear what factors explain this difference. We tested the hypothesis that these attention-getting (AG) sounds are socially learned via transmission between mothers and their offspring. We assessed 158 chimpanzees to determine if they produced AG sounds. A significant association was found between mother and offspring sound production. This association was attributable to individuals who were raised by their biological mother-as opposed to those raised by humans in a nursery environment. These data support the hypothesis that social learning plays a role in the acquisition and use of communicative vocal signals in chimpanzees.     

Mother-infant interactions in captive slow lorises (Nycticebus coucang)

Information is presented about mother-infant interactions and infant development in a rarely studied prosimian primate, the slow loris (Nycticebus coucang). Four dyads were observed, by means of closed circuit TV, in a semi-natural environment for 1 hour per day three times a week. Infants were inactive for the first 6–8 weeks. Although mothers carried infants, they also left them alone for substantial periods of time after the 1st week. Over the 20-week study period, there was a significant decline in ventral contact but not in sitting within 12 inches or engaging in active social interactions. By the end of the study, infants were not yet fully independent. Three of the 4 were primarily responsible for maintaining physical closeness to the mother; they made most of the approaches and mothers made most of the departures. However, only 2 of the 4 infants had assumed responsibility for the initiation and maintenance of social interactions with the mother. By comparison with other nocturnal prosimians of similar size, the rate of development is relatively slow. Unlike many anthropoids, mothers were not strongly protective or rejecting. They did not bring infants back to a fixed location or try to prevent infants from leaving them; and the decline in ventral contact was not accompanied by fights between the pair. The 3 group-living mothers were more protective than the single individually housed mother, and it would seem advisable to isolate mother-infant pairs in laboratory breeding colonies.     

Discovering and learning tool-use for fishing honey by captive chimpanzees

Wild chimpanzees commonly use sticks to fish for termites, ants or honey. This ability seems to be socially transmitted to juveniles by their mothers across generations. In a natural environment, the limited visibility of this behavior with regards to the extent of stick's insertion and about the success or failure in fishing hinders the study of the underlying learning processes. This study explores the discovery and learning of tool use for fishing honey in an artificial hive by a group of four captive chimpanzees. The discovery of tool use was accidental and coactive. The speed with which the group of experimentally naive chimpanzees discovered and learned tool use suggests that wild chimpanzees of different populations independently discovered the fishing behavior. The alpha male and his ally learned before the subordinates. Here, trial-and-error learning was, as in monkeys, the main process allowing the acquisition of the tool-use technique. However, the observation of conspecifics allowed the orientation of the experimentation by the selection of clues. As suggested by Tomaselloet al. (1987). it is the understanding of the function of the tool,i.e. the cause-effect relations between the action of the demonstrator, the type of tool and the task to accomplish which confer to chimpanzees and advantage over monkeys.     

The development of infant play in a captive group of lowland gorillas (Gorilla gorilla gorilla)

Three infant gorillas born at the Yerkes Regional Primate Research Center of Emory University were studied during their first year and one-half of life for various aspects of behavior, including solitary and social play, using both focal animal and one-zero sampling. The appearance of play in these infants followed a developmental trend, beginning with mother-infant play, and followed by solitary play, and then social play among peers. Mothers were initially very vigilant, repeatedly interrupting infant peer play bouts, this relaxing toward the end of the first year. Evidence for a possible sex difference in active social play is presented.     

Mother-infant relations in captive woodchucks (Marmota monax)

Mother-infant relations in three litters of captive woodchucks were studied from birth until about one week after dispersal normally occurs in nature. Weaning correlated with dispersal age and with an increase in aggressive mother-infant relations and a decrease in solicitious behaviour.     

Feeding enrichment and body weight in captive chimpanzees

Although positive behavioral consequences have been attributed to feeding enrichment, physiological changes may also occur. In this study, the body weight records of a large chimpanzee colony were reviewed to determine if body weight was affected by the implementation of a daily enrichment program, including food items offered three to four times per week. Comparing the mean body weight by age groups indicated that the weight of female chimpanzees was significantly greater after feeding enrichment but that male body weight did not differ.     

Synchrony of estrous swelling in captive group-living chimpanzees (Pan troglodytes)

Recent findings suggest that menstrual synchrony may occur in humans and is more dependent on factors of close personal association than simple prox imity. Part I of this study analyzed the estrous cycles of 10 captive group living chimpanzees (Pan troglodytes) housed in two separate groups in the same building. Each group contained at least one male. The mean discrepan cies for (1) the approximate day of ovulation (last day of maximum swelling) and (2) the day of onset of estrous swelling were determined for all possible pairs within groups and compared to the mean discrepancies of pairs between groups. With respect to the probable day of ovulation, the mean discrepancy of animals caged together was 8.0 days and that of animals caged separately was 10. 7 days. Comparing the onset of estrous swelling, the mean between groups was 10.4 days, whereas females caged together averaged only 5.7 days. A repeated-measures analysis of variance indicated a significant group effect in the onset of estrous swelling (F = 5.68,p < 0.05), whereas there was no significant difference between the animals caged together and those caged separately with respect to the last day of maximum swelling (F = 1.37, NS). Part II of the study compared the onset of the first postpar tum estrus (PPE) to the onset of estrus in cagemates. During a 6-year period, 13 females exhibited 33 PPEs while in social contact with cycling females. Of 86 paired comparisons, the PPE onset of 43 (50%) occurred with in 6 days of the swelling onset of a cagemate. The results suggest that, as in other species (including humans), the social contact and time spent together influence the synchrony of chimpanzee estrous cycles, especially in terms of swelling onset. The synchrony of estrous swelling and possible mediation by olfactory and/or hormonal cues are discussed as they relate to chimpanzee social structure and female reproductive strategy.     

Reproductive development and behavior of captive female chimpanzees

The reproductive histories and behavior of six chimpanzees were analyzed in order to evaluate the female reproductive pattern. This analysis indicated that captive females undergo an earlier menarche and an acceleration of subsequent reproductive phases as compared to wild chimpanzees. Menarche occurred between 7.7–9.3 years of age and first conceptions occurred between 8.2–10.7 years of age. Changes in the females' sex skins across menarche, pregnancy, and the menstrual cycle were also evaluated. The fluctuation in sex skin size was shown to have a marked effect on the occurrence of sexual behavior. In addition, the social context and relative familiarity of the chimpanzees affected the choice of sexual partners.     

Treatment of myocardial dysfunction and pulmonary oedema in an infant chimpanzee

Abstract: The care of any critically ill infant requires special technical equipment for monitoring of cardiac and pulmonary functions including mechanical ventilators and blood gas analysers. The present paper describes the treatment of myocardial dysfunction and pulmonary distress, complicated by severe brain oedema in an infant chimpanzee admitted to an intensive care unit in the Department of Neonatology of the Children's Hospital of the University of Leipzig. The condition of the chimpanzee was diagnosed and monitored by standard clinical tooös including radiography, echocardiography, cerebral Doppler sonography and laboratory parameters. The chimpanzee was treated in close cooperation between veterinarians and paediatricians.     

Effects of inbreeding on infant mortality in captive primates

Breeding records for 16 primate colonies representing six families and both suborders were obtained from 10 institutions breeding primates in captivity and from the international studbook on one endangered species. Inbreeding coefficients relative to the founding population were calculated for each individual born. Individuals with an inbreeding coefficient of zero were classified as “noninbred” those with inbreeding coefficients greater than zero, as “inbred.” Infant mortality was defined as all deaths prior to the age of 6 months. Infant mortality of inbred young was higher than that of noninbred young in 15 of the 16 colonies surveyed (P =0.0003, one-tailed sign test). The higher mortality rate of the inbred young was significant by a Fisher’s exact test with a probability less than or equal to 0.05 in five of the individual colonies: Lemur fulvus, Saguinus fuscicollis illigeri, Saguinus fuscicollis, Leontopithecus rosalia,and Mandrillus sphinx.     

Infant mortality in mother-reared captive chimpanzees at Taronga Zoo,Sydney

Infant mortality in mother-reared chimpanzees was examined from the records of Taronga Zoo, Sydney, Australia. Sex-specific mortality probabilities were calculated using standard demographic techniques. Male mortality was found to be considerably higher than female mortality. Using the same techniques, changes in infant mortality over time were calculated, with particular reference to changes that had occurred since the chimpanzees were transferred to a new open air enclosure in 1980. Mortality was found to have decreased dramatically since the move to the new enclosure, but the observed decline was exaggerated by the very high proportion of female infants. The main causes of infant death as ascertained from the zoo records were pneumonia and trauma. In addition, undetermined causes in the first day of life were numerous. An examination of the contexts of infanticide in wild and captive chimpanzees revealed slight differences, but factors such as aggression towards unfamiliar individuals and redirected aggression were common to both. Cannibalism in the zoo has so far been limited to the bodies of stillborn infants.     

Comparative analysis of weight gain,hand/wrist maturation; and dental emergence rates in chimpanzees aged 0–24 months from varying captive environments

Variability during the first 2 years of growth and development is examined in captive chimpanzees. The mixed longitudinal study of 175 animals compares curves of weight, hand/wrist maturation, and dental emergence for groups within the sample which differ in sex, rearing circumstances (mother-reared versus hand-reared), and colony (Primate Foundation of Arizona, White Sands Research Center, and The University of Texas M.D. Anderson Cancer Center Department of Veterinary Sciences in Bastrop, Texas). Comparison of LOWESS fits of the curves, using a conservative jack-knife approach, reveals trends toward significant differences between colonies for weight (with 4 comparisons reaching significance) and between rearing groups for maturation (1 reaching significance). Results of a full versus reduced model approach show the same trends, for which significance is reached in a higher number of comparisons. The latter approach also indicates possible effects of sex and environmental differences on dental emergence rate. Difficulties with both approaches are discussed. It is concluded that the results are suggestive of significant sex and environmental effects on the variables monitored, justifying further analysis and continuation of the study. The study is significant in 1) providing norms specific to sex and rearing and colony environments with which individual colony animals may be compared in the assessment of their development and in 2) providing a standard, based upon data from a larger and more varied captive chimpanzee population than previously available, with which the dental emergence status and hand/wrist maturation of fossil apes and hominids may be compared. © 1996 Wiley-Liss, Inc.     

Sex and species differences in captivereared juvenile chimpanzees and orang-utans

The behavior of nursery-reared juvenile chimpanzees and orang-utans was studied during intraspecific group interactions in large outdoor compounds. Chimpanzees spent more time on the ground, more time in proximity to another and exhibited more slap-hit behavior than the orang-utans. Both groups exhibited only species-typical vocalizations. Males of both species were more assertive in social interactions, whereas females interacted more with inanimate objects. Positive correlations between body weight and the frequency of some social interactions partially confounded interpretation of the sex differences. The results indicate that early experience with adults is not necessary for the development of certain sexually dimorphic and species-typical behavior patterns in juvenile apes. However, early experience with peers seems to facilitate development of these patterns. The results are discussed in relation to available data on the early hormonal and social determinants of behavior in the higher Primates.     

Food transfer between mother and infant chimpanzees of the Mahale Mountains National Park,Tanzania

We studied food transfer between chimpanzee mothers and infants in the Mahale Mountains National Park, Tanzania. The rate of infant solicitation for food dramatically increased in the second year of life, then gradually decreased and, in the seventh year, virtually disappeared. The pattern of the ontogeny of food sharing precisely followed that of solicitation because mothers shared food only when requested to do so by their infants. The success rate of solicitation, however, did not display extreme changes across ages. Food that was difficult to process was shared more frequently because it was more likely to be demanded by infants. We defined food retrieval as an infant’s recovery of leftovers discarded by its mother. Food types retrieved were often those that are difficult to process and were also likely to be shared by mothers. However, infants tended to solicit small, difficult food types for sharing while they often retrieved the remains of large, difficult food types. The function of food sharing and food retrieval lies in an infant’s learning food types that it cannot easily obtain or process by itself. The level of competition for food between mothers and infants remained low throughout infancy. We noted no particular characteristic about foods from which infants were displaced by mothers. As infants grew older, they increased the distance between themselves and mothers that became more aggressive.     

Parental care in captive siamangs (Hylobates syndactylus)

Siamangs exhibit paternal care to the extent that the male of a monogamous unit carries its infant offspring beginning late in the infant's first year of life. Field studies have documented this but without behavioral detail. It has been hypothesized that the transfer is facilitated by a desertion of the infant by the female. An infant siamang born in captivity at the Washington Park Zoo, Portland, Oregon, was observed through its first year of life. The infant transfer to the male was documented in captivity and was associated with a high rate of infant-initiated contact with the male and a high rate of infant retrieval by the female. The study concludes that the infant probably played a key role in facilitating the transfer to the male.     

Nonsocial behavior of captive infant gorillas

Frequencies of eight nonsocial behaviors (object contact, environmental exploration, mouthing, self-directed behavior, display behavior, solitary behavior, rest, and locomotion) were obtained for 20 infant lowland gorillas (Gorilla gorilla gorilla) between 14 and 36 months of age. They lived in 13 groups in 10 zoological collections. Approximately 12 hours of one-zero data were collected on each animal. Behavioral data were analyzed with regard to the following independent variables: rearing history of the focal animal (mother-reared vs. human-reared), time of day (a.m. vs. p.m.), sex of the focal animal, age of the focal animal, and complexity of the physical and social environment. Results indicated significant differences in the frequency of behaviors within each independent variable, including selfdirected behavior, rest, environmental exploration, and display behavior with rearing history. Additional significant differences in the frequencies of behavior were also found, including mouthing behavior and locomotion with infant age.     

Precision grips in young chimpanzees

A precision grip, thumb-finger opposition, has been regarded as an uniquely human trait. Napier's conclusion that chimpanzees were incapable of precision grip was based on two subjects and prehension of a single object (i.e., a grape). The purpose of the present study was to specify grip type and hand use by 13 young chimpanzees to prehend three different-sized food objects. The subjects were laboratory raised (eight males and five females) and ranged in age from 27 to 58 months. An ethogram was devised that comprised 43 different grip types: ten configurations of precision grips were found, in addition to imprecise or inefficient grip types (nine types), thumb-to-finger opposition (10 types), power grips (two types), and a variety of other grips (12 types). Subjects most often prehended were very small-sized (5 mm × 5 mm × 3 mm) or small-sized (10 mm × 10 mm × 3 mm) food objects with precision and imprecise grips. An analysis of latency to prehend, i.e., efficiency, revealed (1) precision grips were equally efficient for all object sizes; (2) power grips were most efficient with the largest object (a grape); (3) with imprecise grips, the left hand was more efficient than the right with small objects, and with power grips the right hand was more efficient than the left for medium-sized objects. No population handedness was observed, but individual handedness was seen in nine subjects for some grip types and some object sizes. This study provides evidence that young chimpanzees preferentially use a true precision grip to prehend small and very small objects. © 1996 Wiley-Liss, Inc.     

Polymorphisms and gross structure of glycophorin genes in common chimpanzees

Using human α glycophorin cDNA probe and six restriction enzymes, we examined the homologues of human glycophorin genes in genomic DNA of 11 unrelated chimpanzees. We show that, in contrast to the human, the chimpanzee exhibits an unusual array of nonrandomly distributed restriction fragment length polymorphisms (RFLP). No clear correlation was found between the RFLP and the V-A-B-D blood-group phenotypes of the subjects, with one possible exception. However, pairs of allelic RFLP occurring at a relatively high frequency were identified. In addition, the homology of chimpanzee glycophorin genes to the human genes was examined using as probes synthetic oligonucleotides specifying distinct regions of human glycophorin genes. We show that the glycophorin gene family in the chimpanzee consists of at least three members that are homologous to the human α, δ, and E genes (glycophorins A, B, and E) and may share a similar gross structure and overall organization. This research was supported by National Institutes of Health Grant GM 16389.