Growth of wild and laboratory born chimpanzees

The skeletal remains of a wild juvenile chimpanzee,Pan troglodytes verus, of known chronological age are measured and found to be smaller than laboratory born and fed juveniles of the same age. Other wild born immature skeletal materials of all the three subspecies ofPan troglodytes, including both known and estimated chronological ages, are also smaller than laboratory born chimpanzees when comparisons are made on corresponding age groups. Differences between wild and laboratory born chimpanzees are larger in the limb bones than in the cranium. Limb bones of laboratory individuals grow earlier than those of wild ones regardless of subspecies. Small limb bone size of wild chimpanzees is discussed in terms of life processes.     

Prelinguistic development of children and chimpanzees

What was unique about our laboratory was the detailed simulation of a human rearing environment for infant chimpanzees, together with continuous, intensive observation and recording of behavioral development. Communication in American Sign Language (ASL) was integrated into this procedure in a way that simulates the teaching of vocal and gestural languages to human children. The result is a comprehensive longitudinal record of the stage by stage development of two-way communication in sign language and its relation to basic aspects of behavioral development such as: locomotion, manipulative skills, observational learning, and social play. In the longitudinal records of five infant chimpanzees, we can trace the patterns of development and also examine the consistency of individual differences through the first five years. The central question is the relation between developing skills in the use of American Sign Language and the rest of behavioral development. To analyze factors that influence development, we have compared records for infant chimpanzees reared in the crossfostering laboratory with records for chimpanzees reared in the wild by their own mothers and chimpanzees reared in cages under conventional laboratory conditions, as well as with records of development for human children, reared in homes and reared in institutions.     

Early signs of language in cross-fostered chimpanzees

In cross-fostering the young of one species are reared by adults of another, as in the classical ethological studies of imprinting and song-learning. In our laboratory, infant chimpanzees were reared under human conditions that included two-way communication in American Sign Language (ASL) the gestural language of the deaf in North America. Here we describe the cross-fostering conditions of this laboratory and the contrast with operant conditioning. We also review the uses and the shapes of the signs in the vocabularies of five cross-fostered chimpanzees, tests demonstrating that the cross-fostered chimpanzees could use signs of ASL to communicate conceptual information to human observers whose only source of information was the signs of the chimpanzees, early development of inflections that resemble the early inflections of deaf human children, evidence based on errors and on inflections for duality of patterning, the continued use of sign language among the chimpanzees even when deprived of human input and the acquisition of signs by the infant Loulis from the cross-fostered chimpanzees.     

Normal vaginal flora in chimpanzees (Pan troglodytes): qualitative and quantitative study

Lactobacilli are the predominant microorganisms in the vaginal flora of human beings, and are known to play an important role in protecting them from genital infections. On the other hand, the composition of the vaginal flora differs among laboratory animal species, and lactobacilli are not the predominant vaginal microorganism in many laboratory animals. We speculated that the vaginal flora of chimpanzees would be more similar to those of human beings than to those of other animal species, because chimpanzees are phylogenetically close to human beings, and their reproductive physiology is similar to that of human beings. To clarify our speculation, we examined the development of the vaginal flora in chimpanzees (Pan troglodytes). Streptococci, lactobacilli, and members of the family Bacteroidaceae were the most predominant bacteria in the vagina of mature chimpanzees (9 to 22 years old). During development of the vaginal flora of chimpanzees, the total number of bacteria increased with age and reached a plateau just before sexual maturity (5 to 7 years of age; juvenile period). Lactobacilli were already one of the predominant bacteria before sexual maturity. In mature chimpanzees, the total number of bacteria (aerobes and anaerobes) in the vagina was highest during the swelling phase of the menstrual cycle. During the swelling phase in mature chimpanzees, streptococci, lactobacilli, and Bacteroidaceae were the most frequently isolated (100%) organisms, and the total number of organisms recovered from vaginal specimens from these three groups was the highest. In mature chimpanzees in which the number of bacteria was the highest, lactobacilli were the predominant bacteria. Taken together, these results suggest that these three bacterial groups (streptococci, lactobacilli, and Bacteroidaceae) are indigenous to the vagina of chimpanzees, and chimpanzees would be the most suitable laboratory animals for studying the role of lactobacilli in the vagina of human beings.     

The effects of early experience on adult copulatory behavior in zoo-born chimpanzees (Pan troglodytes)

This paper examines the relationship between the early rearing experience of zoo-born, zoo-reared chimpanzees (Pan troglodytes) and the subsequent occurrence of successful copulation as adults. Developmental histories were acquired for 71 subjects via questionnaires and phone interviews. The following variables related to aspects of chimpanzees' early rearing experience were examined: (1) Rearing conditions, that is, hand reared alone, reared with siblings or peers, or reared by at least one adult conspecific. (2) Age removed from mother. (3) Sex of subject, and/or (4) participation in shows. Each of these variables was then compared to the subjects' sexual competence, defined here as having been observed to exhibit functional copulatory behavior as adults. Seventy-five percent of the subjects were observed to exhibit functional copulatory behavior on at least one occasion. No single component of rearing was successful in producing sexually competent adults 100% of the time; no rearing condition, as defined in this study, resulted in reproductive failure for all subjects experiencing those conditions. Chimpanzees that were hand reared alone, that is, in the total absence of conspecifics, were least likely to copulate as adults; about half of those chimpanzees that were reared with siblings or peers (and in the absence of adult conspecifics) copulated as adults. Almost 90% of those chimpanzees that were reared with at least one adult conspecific copulated as adults. Chimpanzees removed from their mothers at an early age (less than one year of age) were less likely to reproduce as adults. Male and female chimpanzees were equally likely to reproduce as adults. Participation in shows or demonstrations appeared to have no effect on chimpanzees' ability to copulate as adults. © 1994 Wiley-Liss, Inc.     

The ontogeny of sexual dimorphism in the African apes

The relationship between the growth spurt and the onset of sexual maturity is problematic in nonhuman primates. Growth data on the cranium and postcranium of dentally aged pygmy chimpanzees, common chimpanzees, and gorillas are reported here. In all three species, male means generally exceed female means throughout growth, with the exception that females exhibit a spurt during one dental-age stage when they become generally larger than the males. This female spurt occurs earlier in an absolute and relative sense in the gorillas than the chimpanzees. These growth data support field and laboratory observations suggesting that female gorillas become sexually mature earlier than do female chimpanzees. Gorillas are thus characterized by a greater degree of “sexual bimaturism” than are the chimpanzees. Implications of these differences in terms of size dimorphism, mating systems, and morphology are discussed.     

Establishment,maintenance, and behavior of free-ranging chimpanzees on Ossabaw Island,Georgia, U.S.A.

A small number of adult chimpanzees were released on Ossabaw Island, Georgia, in order to evaluate the feasibility of establishing a free-ranging reproductive colony of chimpanzees in a semitropical North American climate. First, three females and one male were released in June 1972. Following the unexpected deaths of two of these females, four more females were added. Except for one newborn that was removed from the colony, the chimpanzee colony remained intact, and was still in existence as of February 1975. Preparation for and maintenance of the chimpanzees is described. Behavioral adaptations to the environment, and some aspects of chimpanzee social behavior are reported. The potential importance of colonies such as this, for reducing over-exploitation of naturally occurring primate populations is discussed. The financial support of Yerkes Regional Primate Research Center, Emory University, Atlanta, Georgia, and The Pennsylvania State University, Department of Poultry Science, University Park, Pennsylvania, permitted us to make these observations. Funding for planning and construction of the island facilities, and relocation and maintenance of the chimpanzees was provided by a National Institutes of Health grant toGeoffery Bourne, Director of the Center.     

Rehabilitation of research chimpanzees: stress and coping after long-term isolation

We report on the permanent retirement of chimpanzees from biomedical research and on resocialization after long-term social isolation. Our aim was to investigate to what extent behavioral and endocrine measures of stress in deprived laboratory chimpanzees can be improved by a more species-typical social life style. Personality in terms of novelty responses, social dominance after resocialization and hormonal stress susceptibility were affected by the onset of maternal separation of infant chimpanzees and duration of deprivation. Chimpanzees, who were separated from their mothers at a younger age and kept in isolation for more years appeared to be more timid personalities, less socially active, less dominant and more susceptible to stress, as compared to chimpanzees with a less severe deprivation history. However, permanent retirement from biomedical research in combination with therapeutic resocialization maximizing chimpanzees' situation control resulted in reduced fecal cortisol metabolite levels. Our results indicate that chimpanzees can recover from severe social deprivation, and may experience resocialization as less stressful than solitary housing.     

Wounding aggression during the formation and maintenance of captive,multimale chimpanzee groups

Although the multimale community is the natural social organization of chimpanzees, both wild and captive adult males have killed other adult males and infants in intercommunity conflicts and intragroup aggression. Despite the potential for serious aggression, the formation of captive, multimale social groups is desirable for the efficient, long-term, humane housing of chimpanzees in socially and physically enriched environments and for the education of zoo visitors. The University of Texas Science Park (UTSP) has maintained multimale groups of chimpanzees for 14 years. In the UTSP outdoor corral housing, multimale/multifemale social groups of unrelated adult and adolescent chimpanzees (42 F, 46 M) were formed by a series of 397 individual introductions. Wounding aggression was minimal during introductions of females to males or other females and upon male-male introductions of formerly single-caged adolescent and young adult males having had long-term prior visual familiarity. Serious wounding occurred during male-male introductions when there were major discrepancies in the age and social experience of the subjects or when adult, socially experienced males were reintroduced to former group mates following lengthy separations. Male wounding in the eight established long-term groups of 5–11 adults (2–7 males) averaged 1.4 episodes per male-year of residence; 14% of male wounding episodes required surgical therapy. Adult wounding was significantly associated with the presence of one or more group females with maximally tumescent genital swellings. No male-perpetrated infanticides occurred. Not all multimale groupings are successful, but the majority of formerly laboratory-housed chimpanzees may live and reproduce safely in multimale groups. Experience with all-male groups at UTSP suggests that bachelor groups are also practical for long-term housing. © 1995 Wiley-Liss, Inc.     

The role of cross-fostering in sign language studies of chimpanzees

In cross-fostering, the young of one species are reared by adults of another. In our cross-fostering laboratory, two-way communication by means of American Sign Language (ASL) brought the rearing conditions for chimpanzees much closer to those of human children than was possible in earlier studies. At the same time, ASL provided a means by which chimpanzees could express their intelligence in ways that permit closer comparisons with human children. Cross-fostered chimpanzees can communicate with human observers whose only source of information is the American Sign Language (ASL) signs of the chimpanzees. In order to show that the chimpanzees could name natural language categories — that the sign DOG could refer to any dog, FLOWER to any flower, SHOE to any shoe — each test trial was a first trial in that tests slides were presented only once. Analysis of errors showed that two aspects of the signs, gestural form and conceptual category, governed the distribution of errors. Like human adults and human children who sign, the chimpanzees modulated their signs in meaningful ways. Observations in field notes, video tape records, and systematic experiments illustrate how these modulations were related to the verbal and nonverbal, context and how they made signs more visible, more versatile, and more informative.     

Antigenic similarities to HCG subunits among chorionic gonadotropins of nonhuman primates.

Comparison of antigenic similarity between human chorionic gonadotropin (HCG) subunits and the chorionic gonadotropins of six species of nonhuman primates indicates marked similarity of antigenic determinants between both subunits of HCG and the chorionic gonadotropins of chimpanzees, gorillas, and orangutans. Antisera to HCG subunits (alpha or beta) did not cross-react with the chorionic gonadotropins of baboons, macaques, or marmosets. Because of the relative availability of chimpanzees for laboratory studies, we suggest that chimpanzees may be the optimal nonhuman primate model for determining the advisability of vaccinations in man using conjugates of HCG fragments to achieve fertility control or for suppression of HCG-producing neoplasms.     

Comparative locomotor behavior of chimpanzees and bonobos: The influence of morphology on locomotion

Results from a 10 month study of adult male and female bonobos (Pan paniscus) in the Lomako Forest, Zaire, and those from a 7 month study of adult male and female chimpanzees in the Tai Forest, Ivory Coast (Pan troglodytes verus), were compared in order to determine whether there are species differences in locomotor behavior and substrate use and, if so, whether these differences support predictions made on the basis of interspecific morphological differences. Results indicate that bonobos are more arboreal than chimpanzees and that male bonobos are more suspensory than their chimpanzee counterpart. This would be predicted on the basis of male bonobo's longer and more narrow scapula. This particular finding is contrary to the prediction that the bonobo is a “scaled reduced version of a chimpanzee” with little or no positional behavior difference as had been suggested. This study provides the behavioral data necessary to untangle contradictory interpretations of the morphological differences between chimpanzees and bonobos, and raises a previously discussed (Fleagle: Size and Scaling in Primate Biology, pp. 1–19, 1985) but frequently overlooked point–that isometry in allometric studies does not necessarily equate with behavioral equivalence. Several researchers have demonstrated that bonobos and chimpanzees follow the same scaling trends for many features, and are in some sense functionally equivalent, since they manage to feed and reproduce. However, as reflected in their morphologies, they do so through different types and frequencies of locomotor behaviors. © 1993 Wiley-Liss, Inc.     

The ontogeny of human prosociality: behavioral experiments with children aged 3 to 8

Humans regularly engage in prosocial behavior that differs strikingly from that of even our closest living relatives, the chimpanzees (Pan troglodytes). In laboratory settings, chimpanzees are indifferent when given the opportunity to deliver valued rewards to conspecifics, while even very young human children have repeatedly been shown to behave prosocially. Although this broadly suggests that prosocial behavior in chimpanzees differs from that of young human children, the methods used in prior work with children have also differed from the methods used in studies of chimpanzees in potentially crucial ways. Here we test 92 pairs of 3–8-year-old children from urban American (Los Angeles, CA, USA) schools in a face-to-face task that closely parallels tasks used previously with chimpanzees. We found that children were more prosocial than chimpanzees have previously been in similar tasks, and our results suggest that this was driven more by a desire to provide benefits to others than a preference for egalitarian outcomes. We did not find consistent evidence that older children were more prosocial than younger children, implying that younger children behaved more prosocially in the current study than in previous studies in which participants were fully anonymous. These findings strongly suggest that humans are more prosocial than chimpanzees from an early age and that anonymity influences children's prosocial behavior, particularly at the youngest ages.     

Signs of intelligence in cross-fostered chimpanzees

In cross-fostering, the young of one species are reared by adults of another, as in the classical ethological studies of imprinting and song-learning. In our laboratory, infant chimpanzees were reared under human conditions that included two-way communication in American Sign Language (A.S.L.), the gestural language of the deaf in North America. A large body of evidence from five chimpanzees demonstrated stage by stage replication of basic aspects of the acquisition of speech and signs by hearing and deaf children. Here we review evidence that, under double-blind conditions: (i) the chimpanzees communicated information in A.S.L. to human observers; (ii) independent human observers agreed in their identification of the chimpanzee signs, (iii) the chimpanzees could use the signs to refer to natural language categories: DOG for any dog, FLOWER for any flower, SHOE for any shoe.     

Reproductive memory for diagonal and nondiagonal patterns in chimpanzees

Two male juvenile chimpanzees were trained to reproduce from memory geometric patterns composed of lighted cells in a 3 x 3 matrix. In Experiment I, subjects reproduced 3-cell horizontal, vertical and diagonal patterns with either 0- or 5-second delay between stimulus offset and response. Diagonals were more difficult and were more affected by delay than were nondiagonal patterns. The sequence of response to diagonals was less structured than to nondiagonals. In Experiment II, more complex 4-cell patterns were used and, following training, subjects were tested for transfer to new patterns. Again, diagonals were more difficult to reproduce than nondiagonals. Transfer of training to new patterns requiring different motoric responses was successful. Similar to Experiment I, organization of responding was greater for nondiagonals than for diagonals. These results are discussed with regard to the presence of internal representation of visual information in nonhuman primates.     

A novel herpesvirus in the sanctuary chimpanzees on Ngamba Island in Uganda

Background  Recent studies in non-human primates have led to the discovery of novel primate herpesviruses. In order to get more information on herpesvirus infections in apes, we studied wild born captive chimpanzees.
Methods  Chimpanzees of the Ngamba island sanctuary, Uganda, were analyzed with pan-herpes polymerase chain reaction (PCR) targeting the herpesvirus DNA polymerase gene and the glycoprotein B gene. The obtained sequences were connected by long-distance PCR, and analyzed phylogenetically.
Results  Twenty-one of 40 individuals were infected with members of the Gammaherpesvirinae , two of them with a novel member of this subfamily. Phylogenetically, the novel virus fell into a clade of primate rhadinoviruses and the Kaposi sarcoma herpesvirus (human herpesvirus 8), representing a third distinct rhadinovirus in chimpanzees.
Conclusion  Non-human primates harbor several herpesviruses many of which are still unknown. This has implications to management of primates in sanctuaries requiring continuous updates on the management protocols to deal with potential occupational pathogens.     

Food Preferences Among Captive Western Gorillas (Gorilla gorilla gorilla) and Chimpanzees (Pan troglodytes)

I used a zoological park setting to address food preferences among gorillas (Gorilla gorilla gorill) and chimpanzees (Pan troglodytes). Gorillas and chimpanzees are different sizes, and consequently, have been traditionally viewed as ecologically distinct. Sympatric western gorillas and chimpanzees have proved difficult to study in the wild. Limited field data have provided conflicting information about whether gorillas are fundamentally different from chimpanzees in diet and behavior. Fruit eating shapes the behavior of most apes, but it is unclear whether the large-bodied gorillas are an exception to this rule, specifically whether they are less selective and more opportunistic fruit eaters than chimpanzees are. My research provides experimental observational data to complement field data and to better characterize the diets and food preferences of the African apes. During laboratory research at the San Francisco Zoological Gardens, I examined individual and specific differences in food preferences of captive gorillas and chimpanzees via experimental paired-choice food trials with foods that varied in nutritional content. During the study, I offered 2500 paired-food choices to 6 individual gorillas and 2000 additional pairs to them as a group. I also proffered 600 food pairs to 4 individual chimpanzees. Despite expectations of the implications of body size differences for diet, gorillas and chimpanzees exhibited similar food preferences. Both species preferred foods high in non-starch sugars and sugar-to-fiber ratios, and low in total dietary fiber. Neither species avoided foods containing tannins. These data support other suggestions of African apes sharing a frugivorous adaptation.     

Neutralizing antibodies to simian papovavirus SA12 in Old World primates in laboratory colonies: high prevalence in baboons

Sera from 517 laboratory-housed nonhuman primates representing five genera and from 13 laboratory workers were examined for the presence of neutralizing antibodies to SA12 virus. The antibody prevalences were as follows: baboons, 66%; patas and vervet monkeys, 24%; macaques, 8%, and chimpanzees, 2%. The serum of one laboratory worker had antibodies. These results suggest that SA12 virus is a common infection of nonhuman primates in laboratory colonies, especially baboons.     

Gastrointestinal Parasites of Indigenous and Introduced Primate Species of Rubondo Island National Park,Tanzania

Translocation programs releasing animals into the wild need to assess the potential risks associated with the exchange of parasites and other pathogens between native and translocated species. We assessed the composition of the parasite communities in sympatric native and introduced primates. Over a 3-yr period we monitored the gastrointestinal parasites of 3 primate species living in the isolated ecosystem of Rubondo Island National Park, Tanzania: translocated chimpanzees (Pan troglodytes) and guerezas (Colobus guereza) and the indigenous vervets (Chlorocebus aethiops pygerythrus). We detected Troglodytella abrassarti and Enterobius cf. anthropopitheci only in chimpanzees and Chilomastix mesnili in chimpanzees and guerezas. In vervets, we recorded Anatrichosoma sp. and Subulura sp., previously reported in Rubondo chimpanzees. We found Blastocystis sp., Giardia sp., Iodamoeba buetschlii, Entamoeba coli, Entamoeba spp., Trichuris sp., Strongyloides spp., spirurids (cf. Protospirura muricola), and undetermined strongylids in all 3 primate species. Considering the absence of Protospirura muricola in other wild populations of chimpanzees and guerezas, it has probably been acquired from the native vervets, as have Anatrichosoma sp. and Subulura sp. Lower parasite load in Rubondo chimpanzees, in comparison with wild populations at other study sites of this species, might be due to their stay in captivity in Europe before being released on the island. Despite a lack of any apparent health problems from infections in introduced Rubondo primates, parasite monitoring during reintroduction/introduction projects is necessary to decrease potential risks resulting from the exchange of parasites between translocated and native species.     

Hand preference in a captive island group of chimpanzees (Pan troglodytes)

Morphological cerebral asymmetries in chimpanzee brains, similar to those found in humans, in whom they are associated with speech and handedness, suggest the possibility of functional lateralization in the chimpanzee. This possibility was investigated by examining hand preferences in an island group of five chimpanzees on a series of unimanual and bimanual tasks that are diagnostic of human hand and cerebral dominance. Each subject was tested in a double compartment cage on three unimanual nonsequential, three unimanual sequential, and three bimanual coordination tasks. One of the three unimanual sequential tasks was a bar-press task that is analogous to the commonly used human finger-tapping task. For the unimanual tasks, exclusive of the bar-press, the chimpanzees showed a highly individualistic pattern of hand preference that did not change as a function of task complexity. On the bar-press task, four of five subjects produced higher rates with one hand compared to the other; however, relative hand performance on this task was unrelated to hand preference on the other unimanual tasks. For the group of subjects, performance rates did not differ between the left and right hands; however, a practice effect was observed for the right hand in all subjects. The bimanual tasks also revealed a complex pattern of individual handedness, with no trends apparent for the group as a whole. Consistent with previous findings, the results from these tests on this group of five chimpanzees suggest that cerebral morphological asymmetries in the chimpanzee are not associated with motor dominance as reflected in handedness.