Page 29 - Demo

General introduction271Chapter 7 extends this work by testing Bornean orang-utans using a noninvasive eye-tracking setup, similar to the setup that was used to test humans (Chapter 5). Across two experiments, I explored whether orang-utans showed biased immediate and voluntary attention towards flanged males. Furthermore, the design of the second experiment allowed to explore whether the orang-utans showed a stronger attention bias towards certain conspecifics. In Chapter 8, the thesis shifts its focus from visual to auditory information by investigating the effect of orang-utan long calls on female behaviour. More specifically, I describe two case reports of ovulation-induced vocalization and behavioural sensitivity towards male long calls in female Bornean orang-utans. These two cases suggest a potential role for male long calls in orang-utan female mate choice. Furthermore, these cases are the first to indicate that female orangutans might produce ovulation vocalizations that communicate their proceptivity.Finally, Chapter 9 closes the thesis with a general discussion and conclusion, where I emphasize and integrate the main findings from this thesis, and compare my findings in humans and Bornean orang-utans. I also propose relevant directions for future research and discuss practical applications.Tom Roth.indd 27 08-01-2024 10:41