Fish May 'Play' Just Like Other Animals: First Example of a Cichlid Playing

Can you imagine fish playing? It turns out that they may be more social and playful creatures than we once though. Scientists have documented the first example of fish engaging in "play."

"Play is repeated behavior that is incompletely functional in the context or at the age in which it is performed and is initiated voluntarily when the animal or person is in a relaxed or low-stress setting," said Gordon Gurghardt, one of the researchers, in a news release.

In this case, the scientists examined a cichlid fish species. While there are hundreds of species of cichlid fish, including tilapia, the behavior of the species that they studied appears to be unique. The researchers studied and filmed three male fish individually over the course of two years.

The scientists placed a bottom-weighted thermometer in the same tanks as the male fish. Surprisingly, the researchers saw the fish repeatedly striking the thermometer. The presence or absence of food, or other fish within the aquarium or visible in an adjacent aquarium, had no effect on this behavior.

"The quick righting response seemed the primary stimulus factor that maintained the behavior," said Burghardt. "We have observed octopus doing this with balls by pulling them underwater and watching them pop back up again. This reactive feature is common in toys used for children and companion animals."

In fact, the scientists believe that the behavior shown in the fish demonstrates "play." This finding could reveal a bit more about the process of play in general, and shows how play is embedded in species' biology.

"Play is an integral part of life and may make a life worth living," said Burghardt.

The findings are published in the journal Ethology.