Utilization of space by adult and juvenile groups of captive chimpanzees (Pan troglodytes)

A systematic analysis of space utilization in the home enclosures of four adult and three juvenile social groups of chimpanzees (Pan troglodytes) was conducted at the Primate Foundation of Arizona. The locations of all members of each group (excluding nursing infants) were recorded several times per week over a 3-month period. Adult chimpanzees were observed significantly more often in small vs large cages, on upper vs lower levels, and near cage perimeters vs cage centers. Analyses of sex differences in adults revealed that adult females are largely responsible for these space use patterns; adult males show only a significantly higher usage of perimeter areas. Individual differences were found in the habitual use of certain enclosure sites. Juveniles show no spatial patterns with regard to the above parameters but appear to evenly use all available space. Both adults and juveniles were observed to be in contact with mesh barriers more often than with solid walls. These findings suggest important elements that should be incorporated into the caging design of captive chimpanzee facilities.     

Normal hematologic and serum clinical chemistry values for captive chimpanzees (Pan troglodytes)

In the study reported here, reference intervals for hematologic and serum clinical chemistry variables in the chimpanzee (Pan troglodytes) were developed and characterized. Data were collected longitudinally across a 10-year period for 86 subjects at the Primate Foundation of Arizona (PFA). Variables included nine standard hematologic and 25 standard serum clinical chemistry values. An analysis of variance (ANOVA) was used to test for main effects by age and sex. In addition, PFA mean and range values were compared with those published for humans and six other chimpanzee colonies. The ANOVA results suggest an age effect on hematologic (mean corpuscular hemoglobin, mean corpuscular volume, neutrophils) and serum clinical chemical (creatinine, total protein, globulin, tryglycerides, direct bilirubin, iron, (gamma-glutamyltransferase, alanine transaminase, creatine kinase) values. In addition, sex had a main effect on several variables (red blood cells, hemoglobin concentration, hematocrit, uric acid and sodium concentrations, and aspartate transminase and creatine kinase activities); values for males were greater than those for females. Further, human and chimpanzee mean and range values often were indistinguishable from one another. However, changes in human and chimpanzee values associated with age differ and suggest that hematologic and serum clinical chemistry values may be differentially affected by physical and sexual maturation in humans and chimpanzees.     

Effects of cognitive challenge on self-directed behaviors by chimpanzees (Pan troglodytes)

In primates, including humans, scratching and other self-directed behaviors (SDBs) have recently been reported to be differentially displayed as a function of social interactions, anxiety-related drugs, and response outcomes during learning tasks. Yet few studies have focused on the factors influencing SDBs in our closest living relatives, the chimpanzees (Pan troglodytes). Furthermore, no previous experimental study has examined handedness of SDBs as a function of changes in task difficulty. Using matching-to-sample tasks of varying difficulty, the present study examines the effect of manipulations of task difficulty on rates, handedness, and type of SDBs in an experimental study of eight chimpanzees. SDBs were categorized as rubs, gentle scratches, and rough scratches. SDBs increased during difficult discriminations, but only for subjects who started the experiment on an easy discrimination; subjects who started on a difficult discrimination exhibited no differential rates of SDBs as a function of task difficulty. There was a tendency to exhibit relatively more SDBs with the right hand in the more difficult task. Rates of SDBs decreased after auditory feedback signals, suggesting a link between SDBs and uncertainty. Rubs were directed more to the face (trigeminal), and gentle and rough scratches more to the body (spinothalamic), suggesting that face-directed SDBs may index a different motivational basis than scratches. Taken together, these results extend previous research on SDBs to the domain of cognitive stress in nonsocial contexts, demonstrating that SDBs are sensitive to manipulations of task difficulty in chimpanzees.     

Analysis of hematologic findings in healthy and sick adult chimpanzees (Pan troglodytes)

In order to assess the validity of interspecies extrapolation of hematological information, reference values obtained on 63 captive adult chimpanzees were compared with normal values for man. The discriminative power of both chimpanzee and human reference values was tested by the ability of each to identify abnormalities in the blood in 15 sick chimpanzees. The results indicated that human criteria could be applied to most chimpanzee red cell values but species differences were found in erythrocyte sedimentation rates and neutrophil counts.     

Detection and molecular characterization of foamy viruses in Central African chimpanzees of the Pan troglodytes troglodytes and Pan troglodytes vellerosus subspecies

BACKGROUND: Foamy viruses are exogenous retroviruses that are highly endemic in non-human primates (NHPs). Recent studies, mainly performed in North America, indicated frequent simian foamy virus (SFV) infection in persons occupationally exposed to NHPs. This zoonotic infection was demonstrated mainly after bites by chimpanzees [Pan troglodytes (P. t.)] of the West African P. t. verus subspecies in primatology centers or zoos in the USA. METHODS: We studied 32 chimpanzees from the Central African subspecies P. t. troglodytes and P. t. vellerosus, originating from Cameroon (29 cases) or Gabon (3 cases). We screened first plasma or sera of the animals with a Western blot detecting the SFVs Gag doublet proteins. Then, we performed two nested polymerase chain reactions (PCRs) amplifying a fragment of the integrase and LTR regions and, finally, we made phylogenetical analyses on the sequences obtained from the integrase PCR products. RESULTS: By serological and/or molecular assays, we detected foamy viruses (FVs) infection in 14 chimpanzees. Sequence comparison and phylogenetic analyses of a 425 bp fragment of the integrase gene obtained for 10 of the 14 positive apes, demonstrated a wide diversity of new FVs strains that belong phylogenetically either to the P. t. troglodytes or P. t. vellerosus foamy viral clade. CONCLUSIONS: This study shows that chimpanzees living in these areas of Central Africa are infected by several specific foamy viruses. This raises, in such regions, the potential risk of a human retroviral infection of zoonotic origin linked to chimpanzees contacts, as already exemplified for STLV-1 and SIV infections.     

Variables influencing the origins of diverse abnormal behaviors in a large sample of captive chimpanzees (Pan troglodytes)

The developmental origin of abnormal behaviors is generally associated with early rearing environments that lack sufficient physical and sensory stimulation. However, other factors should also be considered. A large sample of captive chimpanzees (128 males and 140 females) was surveyed for the presence or absence of 18 abnormal behaviors. Origin variables included the subject's source (zoo, pet, performer, or laboratory), rearing (mother‐ or hand‐reared), and sex. Animals were assessed while held at the Primate Foundation of Arizona, University of Texas M. D. Anderson Cancer Center, or White Sands Research Center. There was a confound among origin variables; more hand‐reared animals than expected were from laboratories. Logistic regression tested the relationship of rearing and source, with sex as a secondary predictor variable, to each of the abnormal behaviors. There was no clear association between any abnormal behavior and source. However, for coprophagy, relative to animals from the laboratory, zoo animals tended to show a higher prevalence, while performers tended to show a lower prevalence (when rearing and sex were controlled). Rocking and self‐sucking were significantly more likely in hand‐reared animals. Coprophagy and depilation of self were significantly more likely in mother‐reared animals. When rearing and source were statistically controlled, the only significant sex difference was a higher prevalence of coprophagy in females and a higher prevalence of rocking in males. In a second, smaller sample of 25 males and 33 females from Southwest Foundation for Biomedical Research, no significant sex association was found for coprophagy, urophagy, rocking, or self‐depilation. In this second sample, coprophagy was also significantly more likely in mother‐reared than hand‐reared subjects. The association of some abnormal behaviors with mother‐rearing suggests that some form of social learning may be involved in the origin of some of these behavior patterns. This indicates that some abnormal behaviors may not be always be indicative of reduced psychological well‐being in captive chimpanzees. Am. J. Primatol. 48:15–29, 1999. © 1999 Wiley‐Liss, Inc.     

An evaluation of the efficacy of video displays for use with chimpanzees (Pan troglodytes)

Video displays for behavioral research lend themselves particularly well to studies with chimpanzees (Pan troglodytes), as their vision is comparable to humans', yet there has been no formal test of the efficacy of video displays as a form of social information for chimpanzees. To address this, we compared the learning success of chimpanzees shown video footage of a conspecific compared to chimpanzees shown a live conspecific performing the same novel task. Footage of an unfamiliar chimpanzee operating a bidirectional apparatus was presented to 24 chimpanzees (12 males, 12 females), and their responses were compared to those of a further 12 chimpanzees given the same task but with no form of information. Secondly, we also compared the responses of the chimpanzees in the video display condition to responses of eight chimpanzees from a previously published study of ours, in which chimpanzees observed live models. Chimpanzees shown a video display were more successful than those in the control condition and showed comparable success to those that saw a live model. Regarding fine-grained copying (i.e. the direction that the door was pushed), only chimpanzees that observed a live model showed significant matching to the model's methods with their first response. Yet, when all the responses made by the chimpanzees were considered, comparable levels of matching were shown by chimpanzees in both the live and video conditions.     

Blood pressure reference intervals for healthy adult chimpanzees (Pan troglodytes)

Background Cardiovascular disease is the primary cause of morbidity and mortality among captive chimpanzees. But there are no clinical definitions of normotension or hypertension in chimpanzees. Methods We analyzed 1 year of blood pressure (BP) data from a population of 261 healthy captive adult chimpanzees using a consistent set of criteria to ascertain health. Results Systolic BP varied by body weight. Diastolic BP varied by age. Median normotension was 126/63 mmHg, with an upper limit of 147/84 mmHg. We defined categories of pre‐hypertension (148/85—153/88 mmHg) and hypertension (≥154/89 mmHg). The prevalence of elevated BP was 15%. The relative risk of mortality was 2.60, compared to normotensive animals. Conclusions We used contemporary methods from human laboratory medicine to define reliable reference intervals for chimpanzee BP. Results allow accurate diagnosis of hypertension and pre‐hypertension, and demonstrate an effect of elevated BP on mortality.     

The relationship between forage material and levels of coprophagy in captive chimpanzees (Pan troglodytes)

Although coprophagy is practiced in the wild by chimpanzees (Pan troglodytes), it occurs more frequently and under more varied circumstances in captivity. This study was designed to determine if different forage materials and amount of residual undigested grain particles found in the feces might cause an increase in coprophagous behavior in those animals which already exhibited the behavior. A possible effect of availability of seed pits and fibrous leaves for “wadge” making, a typical chimpanzee behavior, on levels of coprophagy was also considered. Observations for coprophagous behavior were conducted on 65 juvenile, adolescent, and adult chimpanzees. Coprophagy levels were significantly lower with popcorn than either chicken scratch or sweet feed. A significant increase in coprophagy was noted for all weeks of forage types when tested against the wadge weeks. Residual grain content analysis showed no significant difference in coprophagous behavior between any of the testing conditions. Decreasing levels of coprophagous behaviors may be assisted by the provision of wadge materials. © 1992 Wiley-Liss, Inc.     

Immunophenotyping of peripheral blood, ranges of serum chemistries and clinical hematology values of healthy chimpanzees (Pan troglodytes)

This paper presents clinical chemistry, hematology and immunophenotyping data from 102 chimpanzees over a 2-year period. The groupings were: 3 years or less, 4-7 years, and 8 + years. These data are intended to augment formerly published information on these parameters and to serve as a concise reference guide for primate veterinarians and researchers for whom these data may be useful. This study has larger samplings than previously published data and more panel constituents by immunophenotyping.     

Response of fecal cortisol to stress in captive chimpanzees (Pan troglodytes)

This study examined whether fecal cortisol could be used as an index of stress responses. The stress responsiveness of fecal cortisol was tested with a stressor known to stimulate adrenal activity, the stress of anesthesia. Daily fecal and urine samples were collected from four captive chimpanzees (Pan troglodytes) before and after anesthetizations with Telazol^®/Ketasat^®. Tests of assay validity indicated that cortisol was measurable in chimpanzee fecal extracts. Fecal cortisol concentrations were significantly elevated 2 days after anesthetization, with elevations in seven of the eight treatments. The posttreatment peak was significantly greater than baseline values in three of the four subjects. Both fecal concentrations and proportionate increases in response to stress were significantly correlated with the corresponding values in urinary cortisol, confirming the stressfulness of these procedures and the stress responsiveness of fecal cortisol. These findings provide evidence for the application of fecal cortisol as a noninvasive index of physiologic stress in nonhuman primates. Am. J. Primatol. 44:57–69, 1998. © 1998 Wiley-Liss, Inc.     

Language-trained chimpanzees (Pan troglodytes) delay gratification by choosing token exchange over immediate reward consumption

Token exchange inherently introduces an element of delay between behavior and reward and so token studies may help us better understand delay of gratification and self-control. To examine this possibility, we presented three language-trained chimpanzees with repeated choices involving different foods that could be eaten immediately or lexigram (graphic symbol) tokens that represented (and could be traded for) foods later. When both options were foods, chimpanzees always chose more preferred foods over less preferred foods. When both options were lexigram tokens representing those same foods, performance remained the same as chimpanzees selected the higher value token and then traded it for food. Then, when faced with choosing a token that could be traded later or choosing a food item that could be eaten immediately, most chimpanzees learned to make whatever response led to the more preferred food. They did this even when that meant selecting a high value lexigram token that could be traded only 2 to 3 min later instead of a medium value, but immediately available, food item. Thus, chimpanzees flexibly selected tokens even though such selections necessarily delayed gratification and required forgoing immediately available food. This finding illustrates the utility of symbolic token exchange for assessing self-control in nonhuman animals.     

Polymerase chain reaction detection of Clostridium perfringens in feces from captive and wild chimpanzees, Pan troglodytes

Background For veterinary management of non‐human primates in captivity, and conservation of wild‐living primates, management of their health risks is necessary. Incidences of pathogenic bacteria in the fecal specimens are considered as one of the useful indicators for non‐invasive health monitoring. Methods We carried out the detection of Clostridium perfringens in feces from captive and wild chimpanzees by the rapid polymerase chain reaction method. Results The bacterium was detected in most fecal specimens (80%) in captive chimpanzees. Contrarily, the detection rate in the wild chimpanzees was low, with 23% (n = 12) of 53 fecal samples from the Bossou group, Guinea, and 1.2% (1/81) in the Mahale group, Tanzania. Conclusions These results show that the intestinal microflora differs between Pan populations under various living conditions, being influenced by their diet and environment.     

Asymmetries in postural control and locomotion in chimpanzees (Pan troglodytes)

Posture and locomotion are two of the most primitive and basic motor manifestations of an organism's behavior. Although the restrictions they impose on other motor functions are evident, few studies have considered the possibility of asymmetries in these behaviors in human and nonhuman primates, and how they might impact other asymmetries at higher functional levels. The aim of the current study was to explore in a group of 10 chimpanzees at the Madrid Zoo-Aquarium the degree of asymmetry in four behaviors related to locomotion (walking, ascending, descending, and brachiating) and four behaviors associated with posture (sitting, lying, hanging, and changing postures). Few subjects showed individual preferences, but significant trends in the group for some of the behaviors were found, including right-hand use when initiating quadruped walking, and left-hand use when descending and hanging. Some significant correlations also emerged: a negative one between walking and descending, and a positive one between walking and brachiating and between sitting and changing postures. No correlations were found between locomotor and postural modes. Although we cannot make generalizations on the population level at this time, these findings highlight the importance of considering postural and locomotion factors when studying motor asymmetries in primates.     

Developing classification in action: II. Young chimpanzees (Pan troglodytes)

The development of spontaneous object manipulation in 5 chimpanzees (Pan troglodytes) from ages 15 to 54 months was investigated, focusing on formal properties of subjects’ acts and the objects they manipulated. Young chimpanzees’ manipulation progress from serial one-at-a-time acts on one object to parallel two-at-a-time acts on two or more objects. With age, simultaneous acts become increasingly transformational and identical or reciprocal to each other. Moreover, the class properties of objects manipulated simultaneously change. When presented with objects belonging to two different classes, subjects shift, with age, from manipulating different objects to manipulating identical or similar objects. In all these respects young chimpanzee’ development is similar to human infants’. In others it differs. Most especially, the onset age is later and the development is slower as well as less structurally complex.     

Familial incidence of multiple births in a colony of chimpanzees (Pan troglodytes)

This paper describes the incidence of multiple births in the Yerkes Chimpanzee colony for a period of about 63 years. Pedigrees are presented for all multiple births. They demonstrate the recurrence of twins in relatively few family lines which can be traced back to a small number of ancestors. The findings suggest that twinning is a family trait in chimpanzees and they support the hypothesis that the incidence of multiple births is genetically influenced in this colony. In addition, a relatively high level of inbreeding may have enhanced the incidence of multiple births in these family lines. Similar findings are known from human populations.     

Grip preference, dermatoglyphics, and hand use in captive chimpanzees (Pan troglodytes)

This paper examined the association between grip type, hand use, and fingerprint patterns in a sample of captive chimpanzees. Grip type for simple reaching was assessed for the left and right hand and classified as thumb-index, middle-index, or single-digit responses. Fingerprint patterns were characterized as whorls, loops, or arches on each finger. The results indicated that chimpanzees exhibit significantly more thumb-index responses for the right compared to the left hand. In addition, thumb-index responses were more prevalent for subjects that had a whorl compared to a loop or arch on their thumb. The results suggest that fingerprint patterns are associated with individual differences in grasping type in chimpanzees as well as some variation in hand use.     

Social behavior and genital swelling in pregnant chimpanzees (Pan troglodytes)

Previous reports of increased sexual activity associated with genital swelling during chimpanzee pregnancy have suggested that the tumescent pregnant female may be regarded as a regularly cycling estrous female. Analysis of additional data from seven pregnant and eight cycling females, however, indicated that tumescent pregnant females differed from cycling females in some social interactions with males. As in earlier reports, pregnant females were more receptive to male-initiated copulatory bouts. In addition, pregnant females initiated grooming bouts with males much less frequently than did cycling females, and males spent less time grooming and less frequently inspected the genitals of pregnant than cycling cagemates. This tendency to decrease social interaction during pregnancy is consistent with field reports that pregnant chimpanzees prefer the company of their offspring and other noncycling females. In addition, the genital swelling patterns of 40 chimpanzee pregnancies were analyzed. Length of gestation averaged 231.5 days. Although a high degree of individual variation existed, females were swollen an average of 41% of the days observed, yet reached maximum swelling only 8.7% of the time. Genital swelling was less frequent during the third trimester, averaging 50.5, 47.9, and 22.6% tumescent days in each trimester. Young pregnant females showed maximum swelling more often than did older females. This finding is discussed with respect to field reports of intercommunity transfer of young, tumescent female chimpanzees.     

Nipple contact in captive black-faced chimpanzees (Pan t troglodytes [Blumenbach, 1779])

Three chimpanzee (Pan t troglodytes) mother-infant dyads were studied from months 3 to 11 of the infants' lives in order to obtain data on nipple contact. Three conclusions were obtained: (1) There were fluctuations in the time spent in nipple contact. (2) Both female offspring were in nipple position for less time than the male offspring. (3) Grooming of the infants by their mothers during nipple contact was observed more frequently in the mother-female offspring pairs.