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Our results suggest that the drawing behaviour of these five orang-utans is not random and that differences among individuals might reflect differences of styles, states of mind, and motivation to draw.ĭrawing behaviour has been studied in non-human primate species such as chimpanzees ( Pan troglodytes), gorillas ( Gorilla gorilla), orang-utans ( Pongo pygmaeus), capuchin monkeys ( Cebus apella), and rhesus macaques ( Macaca mulatta) (for a review, see ). Molly drew less and less as she grew older, and we found a significant difference between drawings produced in winter, when orang-utans were kept inside and had less activity, and those produced during other seasons. Individuals differed in terms of the colours used, the space they filled, and the shapes (fan patterns, circles, or loops) they drew. Our findings reveal evidence of differences in the drawing style of the five individuals as well as creative changes in Molly’s drawing style throughout her lifetime. An analysis of the drawings was carried out after collecting quantitative and qualitative variables. We searched for differences between individuals but also tried to identify possible temporal changes among the drawings of one individual, Molly, who drew almost 1300 drawings from 2006 to 2011. This study analyses 749 drawings by five female Bornean orang-utans ( Pongo pygmaeus) at Tama Zoological Park in Japan. This study is the first to reveal such individual differences and can give some clues about the emergence of drawings in human beings. One individual, Molly, did more complex drawings than other individuals and drew differently according to the seasons and her age. Analyses showed that individuals differ in their drawing style, especially in the colours used, the space they filled, and the shapes they drew. This study is based on 749 drawings recovered from five orang-utans ( Pongo pygmaeus) at Tama Zoological Park in Japan, where caretakers regularly facilitated drawing activities for the apes. This provides a good opportunity to collect drawings by non-human primates and allows for comparative studies between hominids. The monkeys and apes are free to use the materials at their disposal and are not constrained or conditioned to show this behaviour. Drawing has increasingly been proposed as an enrichment activity for captive primates in zoological parks and research institutes.