Interstitial myocardial fibrosis in a captive chimpanzee (Pan troglodytes) population

The clinical and necropsy records of 36 (25 male and 11 female) chimpanzees age 10 to 40 y old that died over a 6-y period (2001 to 2006) were reviewed. All animals had annual physical exams that included electrocardiograms and serial blood pressures. Nine of the 36 animals had a complete cardiac evaluation by a board certified veterinary cardiologist, and 7 of the 36 animals (19%) were diagnosed with some form of cardiomyopathy. Systemic hypertension was noted in 3 cases. Cardiac arrhythmias (ventricular ectopy) were seen in 15 (12 male and 3 female) of the 36 animals (42%). Sudden cardiac death (SCD) occurred in 13 (11 male and 2 female) chimps (36%) and was the leading cause of death (n = 13), followed by renal failure (n = 9) and septicemia (n = 3). Histologic examination of the hearts revealed interstitial myocardial fibrosis (IMF) in 29 chimpanzees (81%), and all of the animals that died suddenly due to cardiac causes had IMF to varying degrees. More data will be needed to identify the possible causes of IMF in captive chimpanzees, and IMF may be associated with arrhythmias and SCD in these animals.     

Factors determining tool-using ability in two captive chimpanzee (Pan troglodytes) colonies

The influence of several determinants of performance in a reaching tool task were studied: rearing history, object experience, and gender. Forty-five chimpanzees between the ages of 7 and 36 years served as subjects. They were chosen from two facilities, each group having different levels of tool experience. Each group was made up of individuals from three rearing conditions: wild born, captive mother reared, and captive nursery reared. Results indicated that wild-born subjects were better at the task than were both groups of captive-born subjects, who performed similarly. Previous experience with reaching tools was not a significant factor in the determination of tool-using ability. Gender differences were not apparent for either group, and the range of ages of chimpanzees tested was not related to tool-using ability.     

Acute appendicitis in a chimpanzee (Pan troglodytes)

BACKGROUND: A 7-year old, female chimpanzee (Pan troglodytes) developed acute abdominal pain and anorexia. An irregular, mineral opacity was identified in the caudal right quadrant of the abdomen on radiographs and computed tomography scan, which appeared to be in the region of the cecal appendage. RESULTS AND CONCLUSIONS: A diagnosis of acute appendicitis was made based on clinical signs, abnormal haematology findings, and consultation with a human radiologist. Exploratory laparotomy was performed and the cecal appendage was removed. On histologic examination, the mucosal epithelium contained eosinophilic and neutrophilic inflammation. The inflammation extended through the tunica muscularis to the serosal surface and adjacent mesentery. The histologic findings were consistent with acute appendicitis in humans. The chimpanzee recovered well from surgery with immediate improvement in clinical signs and no post-operative complications.     

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.     

Social factors influencing choice of food source in a captive group of chimpanzees (Pan troglodytes)

The influence of social factors, including social relationship, kinship, estrous cycle stage and hierarchical rank, on choice of a food source was studied in a group of 16 chimpanzees (Pan troglodytes) maintained in a large, outdoor compound. The subjects chose among three feeding stations that were spatially separated and located along the periphery of the compound. One feeding station was associated with a preferred food (orange), and two stations contained a less-preferred food (commercial chow or biscuit). A significant positive correlation was found between (a) the frequency with which one animal groomed another and the frequency with which they chose the same station during a given trial and (b) the percent of time that subjects were in close proximity and the frequency with which they chose the same station during a given trial, and this result was mediated by kinship. There was a significant difference in same-station choice by the adult male and by a maximally tumescent female compared to the choice when that female was detumescent. Finally, there was no significant correlation between social rank and the percent of trials during which the station associated with the more highly preferred food type was chosen. This study provided quantitative data supporting postulations that factors such as social relationship, kinship, and estrous cycle stage affect the composition of groupings of chimpanzees at feeding stations, and the results are consistent with field observations.     

Intracranial arachnoid cysts in a chimpanzee (Pan troglodytes)

An intracranial arachnoid cyst was detected in a 32-year-old, 44.6-kg, female chimpanzee at the Primate Research Institute, Kyoto University. Magnetic resonance imaging (MRI) and computed tomography (CT) were performed and the cognitive studies in which she participated were reviewed. MRI revealed that the cyst was present in the chimpanzee’s right occipital convexity, and was located in close proximity to the posterior horn of the right lateral ventricle without ventriculomegaly. CT confirmed the presence of the cyst and no apparent signs indicating previous skull fractures were found. The thickness of the mandible was asymmetrical, whereas the temporomandibular joints and dentition were symmetrical. She showed no abnormalities in various cognitive studies since she was 3 years old, except a different behavioural pattern during a recent study, indicating a possible visual field defect. Detailed cognitive studies, long-term observation of her physical condition and follow-up MRI will be continued.     

Effect of solar eclipse on the behavior of a captive group of chimpanzees (Pan troglodytes)

A captive group of chimpanzees, housed in an outdoor compound at the Yerkes Regional Primate Research Center, was observed during the annular solar eclipse of May 30, 1984. The behavior of each animal was recorded using an instantaneous scan-sampling technique (Altmann: Behaviour 49:227–265, 1974). Beginning 2 days prior to the eclipse and continuing through the day following the eclipse, data were collected from 1100 to 1300 hours daily. At 1214 hours on the day of the eclipse, when the sky began to darken and the temperature began to decrease, solitary females and females with infants moved to the top of a climbing structure. As the eclipse progressed, additional chimpanzees began to congregate on the climbing structure and to orient their bodies in the direction of the sun and moon. At 1223 hours, during the period of maximum eclipse, the animals continued to orient their bodies toward the sun and moon and to turn their faces upward. One juvenile stood upright and gestured in the direction of the sun and moon. Sunlight began to increase at 1225 hours, and as it became brighter, the animals began to descend from the climbing structure. The behaviors exhibited by the group during the period of maximum eclipse were not observed prior to or following the eclipse nor as darkness approached at normal, daily sunset. These data indicate that a solar eclipse, a rare and uncommon environmental event, can influence and modulate the behavior of chimpanzees.     

Foreign body urethral obstruction in a chimpanzee (Pan troglodytes)

Background  A 34-year-old, captive-born, vasectomized male chimpanzee ( Pan troglodytes ) presented with lethargy and scrotal swelling.
Methods  Urethral obstruction was diagnosed via urethroscopy.
Results  Removal of the grass stem foreign body resolved the obstruction. Scrotal and preputial ulceration developed from urine scald, which was managed with surgical debridement and antibiotics.
Conclusions  After 7 weeks, the animal was reintroduced to its troup and has been healthy for 11 months.     

Multidimensional auditory stimulus control in a chimpanzee (Pan troglodytes)

An adolescent female chimpanzee (Pan troglodytes) was trained to discriminate auditory compound stimuli differing in tonal frequency and/or tone on-off rate. Following acquisition training and overtraining, she was shifted to multidimensional stimulus control testing using redundant relevant auditory stimulus sets with discriminability of elements in each dimension varied systematically. Although the control by both dimensions changed significantly as a function of discriminability, the degree of dimensional control was stronger in the tone on-off rate than in the tonal frequency. These results clearly demonstrated “attentional” control of the chimpanzee's auditory discrimination behavior and the interaction between two dimensions of auditory stimuli. The author is now at the Department of Psychology, Primate Research Institute, Kyoto University as a transfer student of the Doctor course.     

Muscle architecture of the common chimpanzee (Pan troglodytes): perspectives for investigating chimpanzee behavior

Thorpe et al. (Am J Phys Anthropol 110:179–199, 1999) quantified chimpanzee (Pan troglodytes) muscle architecture and joint moment arms to determine whether they functionally compensated for structural differences between chimpanzees and humans. They observed enough distinction to conclude that musculoskeletal properties were not compensatory and suggested that chimpanzees and humans do not exhibit dynamically similar movements. These investigators based their assessment on unilateral limb musculatures from three male chimpanzees, of which they called one non-adult representative. Factors such as age, sex, and behavioral lateralization may be responsible for variation in chimpanzee muscle architecture, but this is presently unknown. While the full extent of variation in chimpanzee muscle architecture due to such factors cannot be evaluated with data presently available, the present study expands the chimpanzee dataset and provides a preliminary glimpse of the potential relevance of these factors. Thirty-seven forelimb and 36 hind limb muscles were assessed in two chimpanzee cadavers: one unilaterally (right limbs), and one bilaterally. Mass, fiber length, and physiological cross-sectional area (PCSA) are reported for individual muscles and muscle groups. The musculature of an adult female is more similar in architectural patterns to a young male chimpanzee than to humans, particularly when comparing muscle groups. Age- and sex-related intraspecific differences do not obscure chimpanzee-human interspecific differences. Side asymmetry in one chimpanzee, despite consistent forelimb directional asymmetry, also does not exceed the magnitude of chimpanzee-human differences. Left forelimb muscles, on average, usually had higher masses and longer fiber lengths than right, while right forelimb muscles, on average, usually had greater PCSAs than left. Most muscle groups from the left forelimb exhibited greater masses than right groups, but group asymmetry was significant only for the manual digital muscles. The hind limb exhibited less asymmetry than the forelimb in most comparisons. Examination of additional chimpanzees would clarify the full range of inter- and intra-individual variation.     

Integration of a hand-reared chimpanzee (Pan troglodytes) infant into a social group of conspecifics

Rejections of infants among non-human primates occasionally occur in the wild as well as in captive settings. Controlled adoptions of orphans and introductions of individuals into new groups are therefore sometimes necessary in captivity. Consequently, behavioral research on integration procedures and on the acceptance of infants by adoptive mothers is much needed. In this study, the introduction and subsequent adoption were examined in an 18-month-old hand-reared chimpanzee (Pan troglodytes). The infant was introduced into an age/sex-diversified social group of conspecifics at Furuvik Zoo, Gävle, Sweden, and continuous focal data was collected during the final stage of integration, including infant care exhibited by the group members and the infant’s secure base behavior. The infant was successfully integrated into the group and engaged in positive social interactions with all group members. An adult primiparous female chimpanzee formed a bond resembling a mother–infant relationship with the infant, which continues to be maintained at publication. However, the female initially showed very limited interest in the infant. It was, in fact, two other younger female group members that exhibited most infant care. The infant’s secure base behavior patterns indicate that she adapted well to the new circumstances in the chimpanzee group as the integration progressed. This provides evidence that a final adopter does not necessarily initially show maternal interest and that there can be flexibility in maternal behavior in adult chimpanzee females. Moreover, the methods applied employing gradual familiarization with all the group members and the use of an integration enclosure, may have contributed to a successful result. These findings extend our knowledge of introduction procedures in captivity as well as provide information on foster mother–infant attachment in chimpanzees.     

Mhc-DRB diversity of the chimpanzee (Pan troglodytes)

Fifty-four chimpanzee Patr-DRB and five human HLA-DRB second exons were cloned and sequenced from thirty-five chimpanzees and four B-cell lines and compared with known Mhc-DRB sequences of these two species. Equivalents of the HLA-DRB1 ^* 02,-DRB1 ^* 03, -DRB1 ^* 07 allelic lineages and the HLA-DRB3,-DRB4, -DRB5, -DRB6, and -DRB7 loci were all found in the chimpanzee. In addition, two chimpanzee Patr-DRB lineages (Patr-DRBX and -DRBY) were found for which no human counterparts have been described. None of the Patr-DRB sequences is identical to known HLA-DRB sequences. The Patr-DRB1 ^* 0702 and HLA-DRB1 ^* 0701 alleles are the most similar sequences in a comparison between the two species and differ by only two nucleotides out of 246 sequences. Equivalents of the HLA-DRB1 ^* 01,-DRB1 ^* 04, and -DRB1 ^* 09 alleles were not found in our sample of chimpanzees. A per locus comparison of the number of Patr-DRB alleles with the HLA-DRB alleles shows that the Patr-DRB3, -DRB4, -DRB5, and -DRB6 locus are, thus far, more polymorphic than ther human homologs. The polymorphism of the Patr-DRB1 locus seems to be less extensive than that reported for the HLA-DRB1 locus. Nevertheless, the Patr-DRB1 locus seems to be the most polymorphic of the Patr-DRB loci. Phylogenetic analyses indicate that the HLA-DRB1 ^* 09 allele may have originated from a recombination between a Mhc-DRB5 allele and the DRB1 allele of a Mhc-DR7 haplotype. Although recombination seems to increase the diversity of the Patr-DRB alleles, its contribution to the generation of Patr-DRB variation is probably low. Hence, most Patr-DRB diversity presumably accumulated via recurrent point mutations. Finally, two distinct PAtr-DRB haplotypes are deduced, one of which (the chimpanzee equivalent of the HLA-Dr7 haplotype) is probably older than 6–8 million years.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide database and have been assigned the accession numbers Mg6074-Mg6132. Correspondence to: M. Kenter.     

Electrocardiogram abnormalities in captive chimpanzees (Pan troglodytes)

Although cardiovascular disease is the leading cause of death in the captive chimpanzee population, little is known about the prevalence and etiology of heart disease in this species. We reviewed the physical exam records of 265 common chimpanzees (Pan troglodytes) for electrocardiogram abnormalities. During the 24-mo period reviewed (August 2003 through August 2005), 34 animals were diagnosed with cardiac arrhythmias consisting of ventricular arrhythmias, supraventricular arrhythmias, conduction disturbances, mixed arrhythmias, and bradycardia. The incidence of cardiac arrhythmia was significantly higher in male animals, chimpanzees 20 to 39 y old, and those with structural heart disease. Incidence of cardiac arrhythmia was not significantly higher in animals with hypertension, hyperlipidemia, or chronic viral infections. During the retrospective period, 7 animals with cardiac arrhythmias died or were euthanized. Mortality was significantly higher in animals with ventricular arrhythmias compared with those without ventricular arrhythmias. We conclude that in the common chimpanzee, age, male gender, and structural heart disease are risk factors for developing cardiac arrhythmias and that ventricular arrhythmias are risk factors for mortality.     

Perinatal dental development in the chimpanzee (Pan troglodytes)

The synthesis of both ontogenetic and phylogenetic data should provide the ideal explanation of morphologic variation, but for the primate dentition, this has not yet occurred. Information concerning growth and development of primate teeth is lacking, in part because of the paucity of specimens. We have therefore examined the deciduous second molars (dm2) and tooth buds of the permanent first molar (M1) of 12 chimpanzees (Pan troglodytes), aged 6.5 months of gestation to 4 postnatal months. The ordering of cusp calcification was identical to that of other primates. By regression analysis, correlations of mesial and distal widths with buccal, lingual, and mesiodistal lengths were low, most probably because of decreased rates of change (slopes) and the relatively small sample size. Correlations were, however, greater for mandibular than for maxillary dentition and higher for age than for body weight; for both the dm2 and M1, distal moieties increased faster and were more highly correlated with other dental variables and age than were mesial ones. Comparison with data from humans revealed both differences and similarities in the absolute size and growth rate of dental moieties during the perinatal period. As the reasons for ontogenetic variation become understood for individuals, species, and higher taxa, the phylogenetic implications of differential growth should become clearer as well.     

Nevus lipomatosus cutaneus superficialis (Hoffmann-Zurhelle) in a chimpanzee (Pan troglodytes)

BACKGROUND: A 32-year-old, male chimpanzee (Pan troglodytes) kept in a zoo developed a focally extensive, proliferative, cerebriform, dermal mass at the left inner thigh extending to the inguinal region. After surgical removal, the mass recurred and extended progressively over a period of 5 years. METHODS AND RESULTS: At necropsy, a 20 x 20 cm large, well defined, papular and partly verrucous, rubbery mass composed of multiple large, soft nodules measuring up to 4 cm in diameter was observed in the left thigh and inguinal region. Histological examination revealed a multifocal expansion of the dermis by mature adipocytes that were arranged in small islands to large lobular aggregates. Dermal proliferations of adipocytes were almost completely separated from the subcutaneous adipose tissue. CONCLUSIONS: This is the first report of a unique lesion that resembles human Nevus lipomatosus cutaneus superficialis in a chimpanzee and is different from lipoma or liposarcoma.     

Expression of beta-defensin-1 in chimpanzee (Pan troglodytes) airways

In human airways, beta-defensins function in the elimination of various pathogens. They have been identified in a wide range of species. Here we report the identification and expression of chimpanzee beta-defensin-1 (cBD1), which is a homolog of human beta-defensin-1, in chimpanzee airways and skin. The cBD1 cDNA sequence differs by only one synonymous nucleotide substitution compared to the human cDNA sequence. In situ hybridization revealed that in lung tissue beside alveolar macrophages also airway epithelial cells, endothelial cells and type II pneumocytes express cBD1 mRNA. In skin, cBD1 mRNA was expressed in keratinocytes and endothelial cells. Together, these results show similarity in structure and expression pattern and perhaps in function.     

Rapid changes in chimpanzee (Pan troglodytes) urinary cortisol excretion

Behavioral endocrinologists are aware that many hormones exhibit a diurnal rhythm, and attempt to correct for this pattern by collecting physiological samples only during specified time windows of varying lengths. In studies utilizing urinary measures of hormone levels, this window often spans 2 h or longer. In this study, we compared chimpanzee urinary cortisol levels in sample pairs collected within 1 h of each other in an attempt to validate the use of a time window for sample collection. Chimpanzees were housed at the University of Louisiana New Iberia Research Center and trained to urinate into a paper cup on command; a total of 41 sample pairs were included in this analysis. We found that mean cortisol levels in the two sets of samples, collected within 1 h or less of each other, were significantly different; the mean cortisol level of the first set of samples was significantly higher than that of the second set. This hormone's diurnal pattern of secretion accounts for this significant decrease over a very short time period. We conclude that collection methodologies involving time windows of 1 h or longer need to take into account such rapid changes in levels of excreted hormone. We advocate the use of methodological and statistical corrections to decrease the impact of short-term fluctuations in urinary cortisol.     

Predation on mammals by the chimpanzee (Pan troglodytes)

With respect to prey selectivity and predation frequency, chimpanzees (Pan troglodytes) show local differences as well as diachronic variability within the same population. When data on predation from three long-term studies at Mahale, Gombe, and Tai are compared, some differences and similarities emerge; Mahale is more like Gombe than Tai in regard of prey selection but features of hunting at Tai with respect to predation frequency are not conspicuous. The most responsible factor for diversity in prey selectivity is a distinct “prey image” maintained by chimpanzees of different populations, although it is necessary to clarify in future studies why and how such tradition develops. Relative body size of chimpanzees to prey species and/or the degree of cooperation among members of a hunting party may explain the variability in prey size selected at each site, the latter influencing the frequency of successful hunts at the same time. Although various degrees of habituation and different sampling methods including artificial feeding might have obscured the real differences, recent data from the three populations do not seem to be biased greatly by such factors. Nevertheless, it is still difficult to make strict comparisons due to the lack of sufficient standardized data across the three populations on the frequency of hunting and predation. It is suggested that the size or demographic trend of a chimpanzee unit-group, especially the number of adult males included, necessarily influences its hunting frequency as well as its prey profile. It is also suggested that factors which bring these males together into a party (e.g. fruit abundance, swollen females, conflict between unit-groups etc.) strongly affect theactual hunting and kill rates. Other possible factors responsible for the local differences are forest structure (e.g. tree height), skilful “hero” chimpanzees, and competition with sympatric carnivorous animals. A total of at least 32 species have been recorded as prey mammals of chimpanzees from 12 study sites and the most common prey mammals are primates (18 species), of which 13 species are forest monkeys. Forest monkeys, colobine species in particular, are often the most common victims of the predation by chimpanzees at each site. We may point out a tendency toward selective hunting for the forest monkeys in terms of the selectivity of prey fauna among all three subspecies of chimpanzees, including populations living in drier environment. The mode of chimpanzee hunting seems to correspond to the highest available biomass of gregarious, arboreal monkeys in the forest, colobine species in particular. In contrast, bonobos (P. paniscus) are less carnivorous than chimpanzees, only rarely preying on a few species of small mammals. The sharp contrast of the two allied species in their predatory tendencies appears to have something to do with the differences in the structure of primary production between their habitats.