We've seen lots of evidence that various animals use tools. Recently, however, BBC News reports that freshwater stingrays have been using their habitat (the water itself) as a tool in problem-solving tests. In a South American experiment, researchers observed the stingrays using jets of water to get to hidden food. They placed the food in a pipe that was sealed at one end and watched as the stingrays shot water into the pipe to extract the food.

One other fish uses water in a way similar to the stingray. The archer fish squirts water from its mouth to "dislodge prey from leaves above the water's surface." With this in mind, the researchers tested the stingrays and found they also use jets of water to loosen food stuck on the surface of the tank.

What does this mean? Previously, it was assumed that the stingray was a simple animal, one that operated on reflex. Now, it seems the animals have "cognitive abilities to rival birds, reptiles, and mammals," according to the article. At Hebrew University of Jerusalem, Israel scientist Dr. Michael Kuba led the latest stingray research. He says cartilage-skeletoned animals are difficult to study and that might explain our assumptions that they were not great thinkers.

BBC News quotes Dr. Kuba, writing that the stingrays are "members of one of the oldest lines of vertebrates and to know more about their abilities will help us to learn more about the evolution of cognition in vertebrates."

Troubleshooting stingrays using tools
Scientists observe problem-solving in freshwater fish.