Of all the adjectives that people apply the fish, playful may not be at the top of the list. However, just because fish do not seem like the most playful of animals does not mean that they are completely humorless. A recent study published in the journal Ethology found that fish, specifically cichlid species like tilapia, have their own unique meaning of what it is to “play.” In fact, scientists are finding that many animals that were previously thought incapable of play, like some insects, reptiles, and invertebrates, do in fact have leisure activities of their own.
“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 co-author Gordon Burghardt in a press release from The University of Tennessee Knoxville.
Burghardt and his fellow researchers studied several male fish over the course of two years and found that the animals would repeatedly strike a thermometer in the tank during periods of low activity. The thermometer would move backwards like a punching bag and then right itself, and the fish would then strike it again. Hitting the thermometer did not release food or result in any beneficial changes for the fish, yet the animals seemed to enjoy it. Burghardt compared this behavior to other animals that manipulated objects just for the sake of interacting with them.
“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.”
Researchers hope that the study will reveal more about fish behavior. The origin of play in fish and what function it serves is not entirely known, but scientists believe that it is somehow vital to their survival, as it is to ours.
“Play is an integral part of life and may make a life worth living,” Burghardt added.