A freshwater stingray using the tools it has around it
Freshwater stingrays use water as a "tool" in problem-solving tests, scientists reveal for the first time.
Researchers gave South American freshwater stingrays tests to evaluate their problem-solving ability.
The stingrays learned to use jets of water as a tool to extract a meal of hidden food from a plastic pipe.
It reveals that the fish, once thought a "simple reflex animal", has cognitive abilities to rival birds, reptiles and mammals, scientists say.
Scientists from Israel, Austria and the US publish their study in the journal
Tool use in fish is far from anything seen in birds or mammals
Dr Michael Kuba Hebrew University of Jerusalem, Israel
found in many tropical waters such as the Amazon river, are related to ocean stingrays. Like sharks, they have skeletons made of cartilage, rather the bony skeletons of less closely related
In the past, scientists have assumed that such
have limited cognitive abilities, in part because they have been difficult to study, says
Dr Michael Kuba
from the Hebrew University of Jerusalem, Israel who undertook the latest study.
His team tested the ability of captive South American stingrays (Potamotrygon castexi) to solve problems, by setting them a series of underwater tasks.
A stingray uses jets of water to remove food stuck among plants
Using a plastic pipe with one end sealed and containing hidden food, researchers observed how the fish overcame the challenge of getting the meal from the container.
They also tested the fish to see if it could discriminate between black and white ends of the tube.
The stingrays not only performed the tasks well but also demonstrated a range of problem-solving strategies, including using water as a "tool" to obtain the hidden reward.
"Tool use in fish is far from anything seen in
" explains Dr Kuba.
Dr Kuba says that the definition of tool use, using an agent to achieve a goal, was set by cognitive scientist Dr Benjamin Beck in 1980.