Tongue-flicking: an idiosyncratic displacement behaviour in a free-ranging and urban-dwelling population of Balinese long-tailed macaques

This brief report describes the occurrence of an idiosyncratic behaviour, labelled tongue-flicking, that was performed by one subadult male long-tailed macaque living in a free-ranging population in Bali, Indonesia. Tongue-flicking may serve a similar purpose as a displacement behaviour in which the subject sticks his tongue out of his mouth and moves it either slightly up and down or in and out without bringing it all the way back into the mouth. Additionally, while abnor-mal behaviours in non-human animals are almost exclusively reported in captive individuals, the investigation of idiosyncratic behaviours such as tongue-flicking allows us to explore the poten-tial occurrence of abnormal behaviours in free-ranging populations. This preliminary descriptive analysis of tongue-flicking aims to highlight the need for understanding the motivational bases and affective implications (e.g., welfare) of abnormal behaviours in captive and free-living animals.