RESEARCH: Otters juggle stones when they are excited about food

Scientists have shown, in a new study, that otters juggles stones when they are excited about food.  

Scientists think that the behaviour might help to train young otters to learn the skills they will need to help them get food from mussels and clams. For older otters, the behaviour might keep them active and busy. 

The scientists observed zoo otters tossing stones in the air, like juggling stones, while standing or lying on their backs. 

Asian Small-Clawed Otter

Mari-Lisa Allison, the lead scientist from the University of Exerter in the United Kingdom said that hunger might be the reason that otters juggle, or toss, stones in the air. However, she said that the real reason is still unknown. 

She said, “Our strongest finding is that otters juggled more frequently before being fed, indicating that the immediate driver of the behaviour is hunger.More research is needed to investigate the ultimate function of the behaviour.”

The study, published in the journal, Royal Society Open Science, looked at the behaviour of 44 Asian Small-Clawed Otters (Aonyx cinereus) and 6 Smooth-Coated Otters (Lutrogale perspicillata) in captive environments in the zoo.

The Asian Small-Clawed Otters eat crabs and shellfish and the Smooth-Coated Otters eat fish.

The researchers used food puzzles to examine their foraging behaviour (the way the otters hunt for food). The food puzzles included tennis balls with holes to allow the otters to reach inside for food; medicine bottles with the lid on loosely; and two stacked Duplo bricks with meat inside.

Ms Allison said these food puzzles were designed to imitate foraging behaviour. For example, snapping apart the Duplo bricks to get the meat is similar to breaking mussels and clams open to eat the meat inside.

The otters juggled more times when they were hungry, and both juvenile and senior otters juggled more times than adults with offspring.

Ms Allison said: “We hypothesised that juveniles may rock juggle to develop those food extracting skills. When they reach maturity and begin reproducing, their time and energy is devoted to raising their offspring. As such, they may not have the time or energy to play. In senior otters, they no longer have those parental responsibilities, so they may have more time to rock juggle.”

Asian Small-Clawed Otter
Asian Small-Clawed Otter

[Location of photographs: Canberra National Zoo and Aquarium, Australia]

Photographer: Martina Nicolls

Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM

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