Factors influencing deceptive behaviours in Tonkean macaques (Macaca tonkeana)

The complex social environments of primates create opportunities for engaging in tactical deception, especially for subordinate individuals. We analysed the behaviour of subordinate Tonkean macaques with dominant conspecifics in an experimental food competition context. The subordinate macaque could see two pieces of food in a test area, but only one piece was visible to the dominant. Both individuals were released into the test area at the same time or with the subordinate given a short head start on the dominant. Here, based on video analysis of the subordinates' behaviours, we describe and classify functionally deceptive behaviours displayed by subordinates, and report factors that influenced these behaviours. Subordinates used several types of tactical deception, including concealment and distraction, especially when paired with competitors of much higher social rank, and they obtained the hidden food more frequently when they used a combination of tactics rather than only one.