New York, Feb 11 (IANS): You may find crocodiles too intimidating to make your new playmate, but just like us they too think surfing waves, playing ball and going on piggyback rides are fun, a study has found.

Crocodilians engage in all three main types of play distinguished by behaviour specialists: locomotor play, play with objects and social play, said Vladimir Dinets, psychology professor at the University of Tennessee, Knoxville.

Dinets, who has studied crocodiles for a decade, conducted an informal survey of crocodilian-themed groups on social media and various conferences.

Dinets observed a juvenile alligator playing with a river otter.

In rare cases, individual crocodilians have been known to bond so strongly with people that they become playmates for years, the study pointed out.

For example, a man who rescued a crocodile that had been shot in the head became close friends with the animal. They happily played every day until the crocodile's death 20 years later.

"The croc would swim with his human friend, try to startle him by suddenly pretending to attack him or by sneaking up on him from behind, and accept being caressed, hugged, rotated in the water and kissed on the snout," Dinets explained.

Crocodilians have been spotted playing with wooden balls, noisy ceramic bits, streams of water, their prey and debris floating in the water.

Cases of locomotor play include young alligators repeatedly sliding down slopes, crocodiles surfing ocean waves and caimans riding currents of water in their pools.

Observed cases of social play include baby alligators riding on their older friends' backs, baby caimans playfully "courting" each other and a male crocodile giving his lifetime mate rides on his back.

The study was published in the journal Animal Behavior and Cognition.