Maybe Your Pet Fish Wasn’t Suicidal

guppyWhen I was growing up, my brother had a black goldfish that I swear was suicidal — it kept jumping out of its bowl. If someone saw it happen, they’d just scoop the fish off the floor and toss him back into the water. But of course, the day came when the fish made a leap when no one was watching, and it didn’t survive.

Several of my friends have similar stories. And so does Daphne Soares, a biology professor at the University of Maryland College Park. She was studying the brains of Poecilia reticulata, a species of guppy, when one of her research subjects in the lab jumped out of its tank and into her cup of chai.

“Fortunately it was iced chai and it had a lid on, so he stayed alive,” Soares said in a statement.

Soon Soares and colleague Hilary S. Bierman were recording jumping guppies with a hi-speed camera to find out what was going on. Their study appears in PLOS ONE.

As with the fish that jumped into the chai, the guppies didn’t need any prompting to make a leap out of the water. They didn’t have to be chasing after food, racing to escape a predator, or swimming upstream to migrate like a salmon in order to jump. And unlike other fish that are known jumpers, P. reticulata prepared for their leap by swimming slowly backwards. Then they would start their jumping cycle with fast body thrusts that propelled them out of the water at speeds of more than four feet per second, allowing them to leap distances up to eight times their body length.

Aquarium owners may be familiar with P. reticulata because these fish are one of the most popular species sold as pets. Soares and Bierman, though, studied guppies taken directly from their native habitat in the Guanapo River in the mountains of Trinidad. And the researchers suspect that it’s this habitat that may be key for understanding why guppies jump.

In the mountainous region where the guppies live, the fish might encounter small waterfalls or other barriers as they try to move into new territory. Soares and Bierman hypothesize that the guppies evolved the ability to jump spontaneously as a method to aid this dispersal, which would help them to avoid competition with kin, prevent interbreeding, escape predators, or find new sources of food.

So perhaps my brother’s fish wasn’t suicidal after it — maybe it just didn’t like the bowl it lived in and was seeking a new home.

Image courtesy of flickr user Wolfgang_44