Welfare of Apes in Captive Environments: Comments On, and By, a Specific Group of Apes

Accurately determining the proper captive environment for apes requires adequately assessing the psychological similarities between apes and humans. Scientists currently believe apes lack mental complexity (Millikan, 2006), raising questions concerning the evolution of human culture from ape-like societies (Tomasello, 1999) .A long-term cultural study with bonobos suggests less intellectual divergence from humans than currently postulated […]

Token transfers among great apes (Gorilla gorilla, Pongo pygmaeus, Pan paniscus, and Pan troglodytes): Species differences, gestural requests, and reciprocal exchange

Great apes appear to be the nonhuman primates most capable of recognizing trading opportunities and engaging in transfers of commodities with conspecifics. Spontaneous exchange of goods between them has not yet been reported. We tested gorillas (Gorilla gorilla), orangutans (Pongo pygmaeus), bonobos (Pan paniscus), and chimpanzees (Pan troglodytes) in a token-exchange task involving two conspecifics […]

Inferences About the Location of Food in the Great Apes (Pan paniscus, Pan troglodytes, Gorilla gorilla, and Pongo pygmaeus)

Bonobos (Pan paniscus; n 4), chimpanzees (Pan troglodytes; n 12), gorillas (Gorilla gorilla; n 8), and orangutans (Pongo pygmaeus; n 6) were presented with 2 cups (1 baited) and given visual or auditory information about their contents. Visual information consisted of letting subjects look inside the cups. Auditory information consisted of shaking the cup so […]

Piagetian Liquid Conservation in the Great Apes (Pan paniscus, Pan troglodytes, and Pongo pygmaeus)

An understanding of Piagetian liquid conservation was investigated in 4 bonobos (Pan paniscus), 5 chimpanzees (Pan troglodytes), and 5 orangutans (Pongo pygmaeus). The apes were tested in the ability to track the larger of 2 quantities of juice that had undergone various kinds of transformations. The accuracy of the apes’ judgment depended on the shape […]

Searching in the Middle—Capuchins’ (Cebus apella) and Bonobos’ (Pan paniscus) Behavior During a Spatial Search Task

In this study we show that bonobos and capuchin monkeys can learn to search in the middle of a landmark configuration in a small-scale space. Five bonobos (Pan paniscus) and 2 capuchin monkeys (Cebus apella) were tested in a series of experiments with the expansion test paradigm. The primates were trained to search in the […]

Image Scoring in Great Apes

‘Image scoring’ occurs when person A monitors the giving behaviour of person B towards person C.We tested for ‘image scoring’ in chimpanzees, bonobos, gorillas, and orangutans. Subjects passively observed two types of incident: (i) a ‘nice’ person gave grapes to a human beggar, and (ii) a ‘nasty’ person refused to give. The subject witnessed both […]

Interactions between zoo-housed great apes and local wildlife

Although there are published reports of wild chimpanzees, bonobos, and orangutans hunting and consuming vertebrate prey, data pertaining to captive apes remain sparse. In this survey-based study, we evaluate the prevalence and nature of interactions between captive great apes and various indigenous wildlife species that range into their enclosures in North America. Our hypotheses were […]

Differences in between-reinforcer value modulate the selective-value effect in great apes (Pan troglodytes, P. Paniscus, Gorilla gorilla, Pongo abelii)

We investigated how apes allocated their choices between 2 food options that varied in terms of their quantity and quality. Experiment 1 tested whether subjects preferred an AB option over an A option, where the A item is preferred to the B item (e.g., apple + carrot vs. apple). Additionally, we tested whether the length […]