Octopus body language: body patterns of Abdopus capricornicus during social interactions.

Abstract Octopus are well known for their rapidly changing and diverse body patterning achieved through combinations of chromatic, textural and postural components. The function of octopus body patterns includes camouflage for prey ambush and predator avoidance, aposematic display to startle intruders and predators and potentially intraspecific communication. However, as many octopus species are often solitary animals, body patterning during intraspecific social interactions are largely unexplored. Here we start addressing this gap in one diurnal reef-dwelling species, Abdopus capricornicus, by providing the first detailed description of the body patterns and associated components expressed during social interactions in captivity. Importantly, this is the first study aimed at disentangling the body patterns used for camouflage from those used for communication. This was achieved by staging dyadic interactions between octopus pairs under controlled conditions in a bare sand environment devoid of rocks or algae. Furthermore, while most studies on octopus interactions focus on reproductive behaviour, here we recorded the body patterns expressed during both intrasexual (e.g. male-male, female-female) and intersexual interactions. We revealed that some body patterns and components are specifically expressed when octopuses are interacting. Furthermore, A. capricornicus shows the richest body patterning repertoire among coastal octopuses studied so far, including 10 body patterns which comprise 27 chromatic, 8 postural and 10 locomotory components. In addition, 19 types of social encounters were identified. We suggest that the complexity of the reef habitat and of the visual stimuli experienced by A. capricornicus, including social cues deriving from frequent interactions, may contribute to its patterning richness.