Hunger, displacement, or play? Object manipulation behaviour in Asian small-clawed otters (Aonyx cinereus)

Asian small-clawed otters (Aonyx cinereus) engage in intricate activities using their paws for purposes such as food extraction, exploration, and tactile communication within their social group. However, some expressions of these behaviours do not appear to be immediately functional in captive populations. Here, we explore the expression of object manipulation behaviours (OMBs), such as rock manipulation (or juggling); the factors that may be driving their expression; and what OMBs may represent. A troop of six otters was observed at Lincolnshire Wildlife Park (United Kingdom) using camera-traps placed at three key locations in their enclosure: outside of their den, at the main feeding area, and at a rock-garden foraging area. A total of 2895 video clips were analysed using a hierarchical ethogram consisting of the behavioural categories of locomotion, stationary, vocalisation, physical affiliative, sustenance, and OMBs. The most commonly observed behaviours were walking (21.5%), lying (20.8%) and feeding (12.2%). OMBs were observed in 3.9% of total observations. Otters performed OMBs significantly more often outside their den than at the other locations. Grooming was also more frequent at this location. There was a negative association between the expression of OMBs and air temperature. Results suggest that in this otter population, OMBs were more likely an expression of play behaviour, contrasting findings reported elsewhere that rock juggling may be driven by hunger.