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Kaplan, G., & Rogers, L. J. (2002). Patterns of Gazing in Orangutans (Pongo pygmaeus). Int. J. Primatol., 23(3), 501–526.
Abstract: Eyes play an important role in communication amongst humans and animals. However, relatively little is known about specific differences in eye morphology amongst primates and how these features might be associated with social structure and direction of gaze. We present a detailed study of gazing and eye morphology-exposed sclera and surrounding features in orangutans. We measured gazing in rehabilitating orangutans in two contexts: interspecific viewing of the experimenter (with video camera) and intraspecific gazing (between subjects). Our findings show that direct staring is avoided and social looking is limited to certain age/social categories: juveniles engage in more looking at other orangutans than do adults or infants. While orangutans use eye movements in social communication, they avoid the more prolonged mutual gaze that is characteristic of humans, and also apparent in chimpanzees and gorillas. Detailed frame-by-frame analysis of videotapes from field and zoo studies of orangutans revealed that they pay visual attention to both human observers and conspecifics by glancing sideways, with the head turned at an angle away from the subject being observed. Mutual gaze was extremely rare, and we have observed only two incidences of gaze following. Orangutans in captivity appear to use a more restricted pattern of gazes compared to free-living, rehabilitating ones, possibly suggesting the presence of a pathological condition (such as depression) in the captive subjects. Our findings have implications for further investigations of social communication and cognition in orangutans.
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Davidsson T.E., Leonardson L.G., & Marston H.M. (1996). Analysis of cognitive function in animals, the value of SDT. Cognitive Brain Research, 3, 269–277.
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Weed M.R., Taffe M.A., Polis I., Roberts A.C., Robbins T.W., Koob G.F., et al. (1999). Performance norms for a rhesus monkey neuropsychological testing battery: acquisition and long-term performance. Cognitive Brain Research, 8, 185–201.
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Vallortigara G., Regolin L., & Pagni P. (1999). Detour behaviour, imprinting and visual lateralization in the domestic chick. Cognitive Brain Research, 7, 307–320.
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Vallortigara G. (1998). Minds of Their Own. Trends. Cognit. Sci., 2, 118.
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Taylor, J. G. (2001). What do Neuronal Network Models of the Mind Indicate about Animal Consciousness? Animal Welfare, 10, 63–75.
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Lea, S. E. G. (2001). Anticipation and Memory as Criteria for Special Welfare Consideration. Animal Welfare, 10, 195–208.
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Bauer, G. B. (2005). Research Training for Releasable Animals. Conservation Biology, 19, 1779–1789.
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Hunt, G. R., & Gray, R. D. (2004). The crafting of hook tools by wild New Caledonian crows. Proc. Roy. Soc. Lond. B Biol. Sci., 271, S88–S90.
Abstract: The 'crafting' of tools involves (i) selection of appropriate raw material, (ii) preparatory trimming and (iii) fine, three-dimensional sculpting. Its evolution is technologically important because it allows the open-ended development of tools. New Caledonian crows manufacture an impressive range of stick and leaf tools. We previously reported that their toolkit included hooked implements made from leafy twigs, although their manufacture had never been closely observed. We describe the manufacture of 10 hooked-twig tools by an adult crow and its dependent juvenile. To make all 10 tools, the crows carried out a relatively invariant three-step sequence of complex manipulations that involved (i) the selection of raw material, (ii) trimming and (iii) a lengthy sculpting of the hook. Hooked-twig manufacture contrasts with the lack of sculpting in the making of wooden tools by other non-humans such as chimpanzees and woodpecker finches. This fine, three-stage crafting process removes another alleged difference between humans and other animals.
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Huizinga, H. A., van der Werf, J. H. J., Korver, S., & van der Meij, G. J. W. (1991). Stationary performance testing of stallions from the Dutch Warmblood riding horse population. 1. Estimated genetic parameters of scored traits and the genetic relation with dressage and jumping competition from offspring of breeding stallions. Livestock Production Science, 27(2-3), 231–244.
Abstract: The stationary performance testing (SPT) of stallions as breeding candidates in the Dutch Warmblood riding horse population is evaluated. Genetic and phenotypic parameters of traits scored during SPT and the genetic correlation of these traits with performances in dressage and jumping competition from offspring of breeding stallions are estimated. Data from 1978-1988 are used, covering scores from 337 3-year-old stallions. Eight subjectively scored traits are considered. These traits are: walk; trot; canter; riding ability; show jumping; free jumping; cross country; character. SPT lasts for a period of 100 days. Data from SPT are analysed using an animal model. The relations between SPT of stallions and performances in jumping and dressage competition are analysed with an animal model for SPT data and a sire model for competition data. Variance and covariance components are estimated by restricted maximum likelihood (REML) procedures. Estimates of heritability are high (0.64) for gaits and riding ability, intermediate (0.41) for cross country and medium-high (0.31) for jumping. Estimated genetic correlation between show jumping scored during SPT and jumping in competition from offspring of breeding stallions is 0.84; for dressage this relation is 0.83. Some possible bias due to selection and the subjectivity of scoring is discussed. It is indicated that selection on SPT of stallions before entering breeding service is an effective tool to breed for ability of performance in competition.
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