London - Even ruthless predators need to have fun in their downtime.
Crocodiles may be among the most frightening of creatures, but research suggests that they enjoy surfing, playing with balls and giving piggybacks to their friends.
Vladimir Dinets, a professor of psychology at the University of Tennessee, has studied crocodiles for a decade and insists they are big softies. In the first scientific study of crocodiles at play, he found they were capable of forming playful relationships, not only with each other but with other species such as river otters and even humans.
"A man who rescued a crocodile that had been shot became close friends with the animal," said Professor Dinets. "The croc would swim with his human friend, trying to startle him by suddenly pretending to attack him or by sneaking up on him from behind, and accept being hugged, and kissed on the snout."
The academic has identified three ways in which the crocodilian family has fun.
Most commonly, they play with objects such as balls, floating debris such as twigs, grass and flowers, streams of water, ceramic objects and even dead animals. In one case, a crocodile spent 25 minutes throwing the carcass of a hippopotamus calf in the air, then "spinning and jumping and splashing" before walking off without taking a bite.
Professor Dinets also observed baby alligators riding on older friends' backs and a male crocodile carrying his lifetime mate the same way.
Crocodiles also engage in "locomotor" play, engaging in unnecessary movement for fun. Examples include young alligators repeatedly sliding down slopes and crocodiles surfing ocean waves.
The research is published in Animal Behaviour and Cognition.