Begging with a Purpose? Testing Behavioural Hallmarks of First-Order Intentionality in Free-ranging Hanuman Langurs

Abstract

Intentional communication has been studied extensively in primates, yet evidence from free-ranging non-ape species remains limited. Human-directed food-solicitation gestures in Hanuman langurs (Semnopithecus entellus) have recently been described, but whether these behaviours exhibit behavioural hallmarks associated with first-order intentionality remains unknown. Here, we experimentally investigated the presence of these hallmarks in free-ranging Hanuman langurs across six anthropogenic sites in southern West Bengal, India. We conducted 360 experimental and control trials and quantified behavioural markers commonly used to operationalize intentional communication. Experimental trials elicited audience checking, recipient-directed orientation, rapid approach responses, food-solicitation gestures and gestural flexibility, whereas these behaviours were rare or absent in control trials. Differences between experimental and control conditions were significant across all six study sites. Signalling also ceased following food acquisition, consistent with the stopping rule associated with an Apparently Satisfactory Outcome. Our findings demonstrate the presence of multiple behavioural hallmarks linked to first-order intentionality in the human-directed gestural communication of free-ranging Hanuman langurs. These results extend the study of intentionality beyond apes and provide new insights into the evolutionary distribution of intentionality-related traits across primates.