Stingray uses tool to get food

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Stingrays can now be added to the list of tool-using animals, according to research to be published in an upcoming issue of the journal Animal Cognition.

Michael Kuba, Ruth Byrne and Gordon Burghardt tested the cognitive abilities of the Vermiculate river stingray (Potamotrygon castexi) using a series of pipes in their aquarium and found them to be capable of tool use, in addition to being capable of learning rapidly in a discrimination/error correction task.

The authors used five stingrays from the Vienna Zoo in their experiments, and placed food in plastic pipes to train the fish to feed from them. 

The authors then closed off one end of the pipe with a metal mesh marking the closed end with black tape and the open end with white tape. Food was placed at the open end of the pipe, and each stingray was then given three minutes to locate the food item. 

The authors used video to analyse the direction of approach, the duration of the trials, initial and final choices, and the strategy used to retrieve the food from the pipe.

The authors found that some of the stingrays were able to associate the visual cue (black/white tape) with the food item and feed from the correct end of the pipe, while the others were capable of learning by trial and error, with the error rate dropping with each successive experiment. 

The authors also found that the stingrays used a variety of methods to extract the food item from within the pipe, ranging from undulating fin movements to suction to water jets blown into the pipe.  This last method qualified as tool usage (using an agent to achieve a goal).

The results of the study showed that elasmobranchs (sharks and rays) possess cognitive abilities that rival those of bony fishes, or even birds and mammals.

For more information, see the paper: Kuba, MJ, RA Byrne and GM Burghadt (2010) A new method for studying problem solving and tool use in stingrays (Potamotrygon castexi). Animal Cognition doi: 10.1007/s10071-009-0301-5