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 more when “hungry”, but frequent jugglers did not solve food
puzzles faster. Our results suggest that rock juggling may be a
misdirected behaviour when hungry and may facilitate juveniles’ motor
development, but it appears unrelated to foraging skills. We suggest
future studies to reveal the ontogeny, evolution and welfare implications
of this object play behaviour.