The drivers and functions of rock juggling in otters

Object play refers to the seemingly non-functional manipulation of inanimate items when in a relaxed state. In juveniles, object play may help develop skills to aid survival. However, why adults show object play remains poorly understood. We studied potential drivers and functions of the well-known object play behaviour of rock juggling in Asian small-clawed (Aonyx cinereus) and smooth-coated (Lutrogale perspicillata) otters. These are closely related species, but Asian small-clawed otters perform extractive foraging movements to exploit crabs and shellfish while smooth-coated otters forage on fish. We thus predicted that frequent rock jugglers might be better at solving extractive foraging puzzles in the first species, but not the latter. We also assessed whether species, age, sex and hunger correlated with rock-juggling frequency. We found that juvenile and senior otters juggled more than adults. However, rock-juggling frequency did not differ between species or sexes. Otters juggled ...