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Tracking the displacement of objects: a series of tasks with great apes (Pan troglodytes, Pan paniscus, Gorilla gorilla, and Pongo pygmaeus) and young children (Homo sapiens).

The authors administered a series of object displacement tasks to 24 great apes and 24 30-month-old children (Homo sapiens). Objects were placed under 1 or 2 of 3 cups by visible or invisible displacements. The series included 6 tasks: delayed response, inhibition test, A not B, rotations, transpositions, and object permanence. Apes and children solved most tasks performing at comparable levels except in the transposition task, in which apes performed better than children. Ape species performed at comparable levels in all tasks except in single transpositions, in which chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) performed better than gorillas (Gorilla gorilla) and orangutans (Pongo pygmeaus). All species found nonadjacent trials and rotations especially difficult. The number of elements that changed locations, the type of displacement, and having to inhibit predominant reaching responses were factors that negatively affected the subjects' performance.

Animals↗

Does space in the jaw influence the timing of molar crown initiation? A model using baboons (Papio anubis) and great apes (Pan troglodytes, Pan paniscus).

Radiographic and histological studies of baboon (Papio hamadryas, P. anubis) and chimpanzee (Pan troglodytes) permanent tooth development have found that periods of molar crown mineralization overlap markedly in chimpanzees but are staggered in baboons. Here we test the hypothesis that these intertaxon differences in molar initiation are primarily due to the space available in the mandibles of each species for these teeth. This study includes radiographic, linear measurement, and three-dimensional (3D) coordinate landmark data taken from baboon (Papio anubis n=51) and great ape (Pan paniscus n=43, P. troglodytes n=60) mandibles and permanent molars across a broad developmental range for each taxon. Unexpectedly, 3D multivariate statistical shape analysis of the molar crypt, crown, and root data shows that all three species trajectories of molar row shape change are indistinguishable from each other. Qualitative analysis of these 3D data reveals subtle and inconclusive intergeneric differences in the space maintained between adjacent molars during growth. The space distal to each newly initiated molar is slightly greater in the baboon. Bivariate analyses comparing molar row and mandibular corpus proportions in Papio and Pan fail to show clear or consistent taxonomic differences in the ratio of space afforded developing molars in the alveolar bone. Thus, there is a poor correlation between mandibular proportion and both intermolar spacing and 3D molar development pattern. Contrary to earlier studies, these results suggest that pattern of molar crown initiation and temporal overlap of adjacent mineralizing crowns is not significantly different between Papio and Pan. This may be due in part to the inclusion here of not only 3D molar crown data but also 3D molar crypt data. This study strongly refutes the hypothesis that space available in the mandible directly underlies different times of permanent molar crown initiation between Papio and Pan.

Animals↗

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.

Amino Acid Sequence↗

Performance in a tool-using task by common chimpanzees (Pan troglodytes), bonobos (Pan paniscus), an orangutan (Pongo pygmaeus), and capuchin monkeys (Cebus apella).

Performance by individual animals of three species of great apes (Pan troglodytes, Pan paniscus, and Pongo pygmaeus) and capuchin monkeys (Cebus apella) was assessed by presenting a food treat inside a clear tube. The subjects readily used a straight stick to obtain the food. When sticks were bundled together, the apes immediately unwrapped the bundle to obtain an individual stick, whereas capuchins attempted to insert the bundled sticks. When a misshapen stick was provided, apes, but not capuchins, showed an improvement in terms of modifying the misshapen stick before insertion. Our results indicate that all these species can solve these tasks. However, only the performance of apes is consistent with emerging comprehension of the causal relations required for the avoidance of errors in the more complex tasks.

Animals↗

The chimpanzee-specific pericentric inversions that distinguish humans and chimpanzees have identical breakpoints in Pan troglodytes and Pan paniscus.

Seven of nine pericentric inversions that distinguish human (HSA) and chimpanzee karyotypes are chimpanzee-specific. In this study we investigated whether the two extant chimpanzee species, Pan troglodytes (common chimpanzee) and Pan paniscus (bonobo), share exactly the same pericentric inversions. The methods applied were FISH with breakpoint-spanning BAC/PAC clones and PCR analyses of the breakpoint junction sequences. Our findings for the homologues to HSA 4, 5, 9, 12, 16, and 17 confirm for the first time at the sequence level that these pericentric inversions have identical breakpoints in the common chimpanzee and the bonobo. Therefore, these inversions predate the separation of the two chimpanzee species 0.86-2 Mya. Further, the inversions distinguishing human and chimpanzee karyotypes may be regarded as early acquisitions, such that they are likely to have been present at the time of human/chimpanzee divergence. According to the chromosomal speciation theory the inversions themselves could have promoted human speciation.

Animals↗

Strategies used to combine seriated cups by chimpanzees (Pan troglodytes), bonobos (Pan paniscus), and capuchins (Cebus apella).

The authors investigated strategies used to combine seriated cups by apes (Pan troglodytes and P. paniscus) and monkeys (Cebus apella) using a protocol reported in P. M. Greenfield, K. Nelson, and E. Saltzman's (1972) study with children. It was hypothesized that apes would exhibit more hierarchical combinations of cups than monkeys, given apes' language capacity, and that apes would seriate the cups more efficiently than monkeys. As predicted, apes made many structures with the cups using a variety of strategies, and monkeys rarely combined the cups. After a training phase to orient monkeys to the task, the 2 genera did not differ in the strategies used to combine the cups or in efficiency in seriating the cups. Success in this task suggests that sensorimotor versions of hierarchically organized combinatorial activity are well within apes' and monkeys' abilities.

Animals↗

Natural genital herpesvirus hominis infection in chimpanzees (Pan troglodytes and Pan paniscus).

Type 2 Herpesvirus hominis was isolated from pustulovesicular lesions on the external genitalia of two chimpanzees. Histopathologic examination of biopsy specimens from both animals revealed typical herpetic changes which included necrosis, superficial ulceration acute inflammatory cell infiltration, multinucleated syncytial giant cells, and intranuclear inclusions. Large numbers of herpes-type viruses were demonstrated by electron microscopy in biopsy specimens from both animals. Serologic studies also demonstrated infection of these animals with Herpesvirus hominis.

Animals↗

Bipedality in chimpanzee (Pan troglodytes) and bonobo (Pan paniscus): testing hypotheses on the evolution of bipedalism.

A host of ecological, anatomical, and physiological selective pressures are hypothesized to have played a role in the evolution of hominid bipedalism. A referential model, based on the chimpanzee (Pan troglodytes) and bonobo (Pan paniscus), was used to test through experimental manipulation four hypotheses on the evolution of hominid bipedalism. The introduction of food piles (Carry hypothesis) increased locomotor bipedality in both species. Neither the introduction of branches (Display hypothesis) nor the construction of visual barriers (Vigilance hypothesis) altered bipedality in either species. Introduction of raised foraging structures (Forage hypothesis) increased postural bipedality in chimpanzees. These experimental manipulations provided support for carrying of portable objects and foraging on elevated food-items as plausible mechanisms that shaped bipedalism in hominids.

Animals↗

How the great apes (Pan troglodytes, Pongo pygmaeus, Pan paniscus, and Gorilla gorilla) perform on the reversed contingency task: the effects of food quantity and food visibility.

S. T. Boysen and G. G. Berntson (1995) found that chimpanzees performed poorly on a reversed contingency task in which they had to point to the smaller of 2 food quantities to acquire the larger quantity. The authors compared the performance of 4 great ape species (Pan troglodytes, Pongo pygmaeus, Pan paniscus, and Gorilla gorilla) on the reversed contingency task while manipulating food quantity (0-4 or 1-4) and food visibility (visible pairs or covered pairs). Results showed no systematic species differences but large individual differences. Some individuals of each species were able to solve the reversed contingency task. Both quantity and visibility of the food items had a significant effect on performance. Subjects performed better when the disparity between quantities was smaller and the quantities were not directly visible.

Age Factors↗

Development of self-recognition in chimpanzees (Pan troglodytes).

Chimpanzees (Pan troglodytes) demonstrate the ability to recognize themselves in mirrors, yet investigations of the development of self-recognition in chimpanzees are sparse. Twelve young chimpanzees, grouped by age, were given mirror exposure and tested for self-recognition and contingent movement. All 6 juveniles, 4 and 5 years old, exhibited mirror-guided, mark-directed behavior and clear evidence of self-recognition. In contrast, among the infants, only the oldest group of 2 1/2-year-olds exhibited clear evidence of self-recognition. All chimpanzees exhibited both self-directed behaviors and contingent movements. These results suggest that self-recognition occurs at a slightly older age in chimpanzees than in human infants. In humans, self-recognition is linked with other cognitive abilities. The results conform to the general pattern that great apes exhibit many cognitive skills comparable to those of 2-year-old humans.

Affect↗

Responses to a simple barter task in chimpanzees, Pan troglodytes.

Chimpanzees (Pan troglodytes) frequently participate in social exchange involving multiple goods and services of variable value, yet they have not been tested in a formalized situation to see whether they can barter using multiple tokens and rewards. We set up a simple barter economy with two tokens and two associated rewards and tested chimpanzees on their ability to obtain rewards by returning the matching token in situations in which their access to tokens was unlimited or limited. Chimpanzees easily learned to associate value with the tokens, as expected, and did barter, but followed a simple strategy of favoring the higher-value token, regardless of the reward proffered, instead of a more complex but more effective strategy of returning the token that matched the reward. This response is similar to that shown by capuchin monkeys in our previous study. We speculate that this response, while not ideal, may be sufficient to allow for stability of the social exchange system in these primates, and that the importance of social barter to both species may have led to this convergence of strategies.

Analysis of Variance↗

Treatment regimen for air sacculitis in the chimpanzee (Pan troglodytes).

Six champanzees (Pan troglodytes) developed air sacculitis. Except for air sac distension and malodorous breath, clinical signs were rare. A variety of organisms, mainly enteric, were isolated from the air sacs. Only one case was treated surgically. Other cases were treated by the conservative method of irrigation which worked well.

Animals↗

Spontaneous discrimination of natural stimuli by chimpanzees (Pan troglodytes).

Six chimpanzees (Pan troglodytes) were presented with pairs of color photographic images of 5 different categories of animals (cat, chimp, gorilla, tiger, fish). The subjects responded to each pair using symbols for "same" and "different." Both within- and between-category discriminations were tested, and all chimpanzees classified the image pairs in accordance with the 5 experimenter-defined categories under conditions of nondifferential reinforcement. Although previous studies have demonstrated identification or discrimination of natural categories by nonhuman animals, subjects were typically differentially reinforced for their responses. The present findings demonstrate that chimpanzees can classify natural objects spontaneously and that such classifications may be similar to those that would be observed in human subjects.

Animals↗

Numerical competence in a chimpanzee (Pan troglodytes).

A chimpanzee (Pan troglodytes), trained to count foods and objects by using Arabic numbers, demonstrated the ability to sum arrays of 0-4 food items placed in 2 of 3 possible sites. To address representational use of numbers, we next baited sites with Arabic numbers as stimuli. In both cases performance was significantly above chance from the first sessions, which suggests that without explicit training in combining arrays, the animal was able to select the correct arithmetic sum for arrays of foods or Arabic numbers under novel test conditions. These findings demonstrate that counting strategies and the representational use of numbers lie within the cognitive domain of the chimpanzee and compare favorably with the spontaneous use of addition algorithms demonstrated in preschool children.

Animals↗

Simian scribbles: a reappraisal of drawing in the chimpanzee (Pan troglodytes).

Three chimpanzees (Pan troglodytes) were provided with 18 different stimulus pages for drawing. The resulting 618 drawings were coded for drawn marks, and results were compared with early reports on ape drawing (Morris, 1962; Schiller, 1951) and with more recent systematic studies (Smith, 1973). The findings of the present study confirm Smith's observations of a tendency for the animals to draw closer to the center and toward the bottom of the page. No evidence for perceptual balancing was observed in drawings produced on pages with lateral figures, nor was any evidence for closure apparent with complex figures. The present results agree with earlier findings that chimpanzees will engage in drawing activities without training or reinforcement, and this behavior may reflect their intrinsic interest in exploratory and manipulative play.

Animals↗

Comprehension of cause-effect relations in a tool-using task by chimpanzees (Pan troglodytes).

Five chimpanzees (Pan troglodytes) were tested to assess their understanding of causality in a tool task. The task consisted of a transparent tube with a trap-hole drilled in its middle. A reward was randomly placed on either side of the hole. Depending on which side the chimpanzee inserted the stick into, the candy was either pushed out of the tube or into the trap. In Experiment 1, the success rate of 2 chimpanzees rose highly above chance, but that of the other subjects did not. Results show that the 2 successful chimpanzees selected the correct side for insertion beforehand. Experiment 2 ruled out the possibility that their success was due to a distance-based associative rule, and the results favor an alternative hypothesis that relates success to an understanding of the causal relation between the tool-using action and its outcome.

Animals↗