Tag Archives: Otters

When otters play with rocks, it’s because they’re excited about food

The otters’ playful juggling of rocks has been reported many times. Whether it’s in the wild, at a zoo, or an animal sanctuary, the little creatures have often been seen playing with rocks — throwing them into the air and skillfully catching them, or rolling the rocks around their necks.

Now, researchers believe they know why otters do this: they’re excited about food.

Researchers from the University of Exeter did what we all secretly crave to do: they spent a lot of time watching otters playing. Of course, it wasn’t for the fun of it — they were looking to see why captive otters tend to play with stones, commonly referred to as “rock juggling”.

Otters are social creatures, learning by copying and mimicking each other. It makes sense that such behavior would have been passed from generation to generation, but why did it emerge in the first place? Researchers suspected that it might help otters practice their dexterity, enabling them to improve their foraging skills (such as cracking mussels and clams), but this doesn’t seem to really be the case.

When researchers gave otters a series of puzzles to solve (which were rewarded with food, of course), otters that spent more time playing with rocks did not seem to fare any better.

The three novel extractive food puzzle types presented to each otter group.

Instead, it seems that otters tend to juggle with rocks more when it’s close to their feeding time, which led researchers to believe that they’re just excited about food — and let’s face it, who isn’t?

However, while hunger is a factor in this behavior, it’s still not clear just what drove its emergence in the first place. Mari-Lisa Allison, lead author of the study said:

“Zoo visitors are often enthralled by the otters’ playfulness. Surprisingly, very few studies have investigated why otters are so keen to juggle stones. Our study provides a glimpse into this fascinating behaviour. While hunger is likely to drive rock juggling in the moment, the ultimate function of the behaviour is still a mystery.”

Overall, rock juggling frequency appeared to increase with age, which may be a way to keep their brains active and to maintain the skills they need to survive in the wild. It could also be that older otters don’t have any parental responsibilities, which leaves them with more free time to be playful. The frequency of rock pay also depends on context, sex, and species, researchers note.

Juggle rate did not predict an otter’s ability to solve food extraction puzzles, suggesting that rock juggling does not enhance food extraction ability. Senior author Dr. Neeltje Boogert added:

“While it did not appear that frequent jugglers solved food puzzles faster, more research is needed to exclude the ‘practice makes perfect’ hypothesis to explain rock juggling in otters.”

Journal Reference: The drivers and functions of rock juggling in otters, Royal Society Open Scienceroyalsocietypublishing.org/doi/10.1098/rsos.200141

Some otters learn how to solve problems by observing other otters

Otters are actually copycats. They solve puzzles by watching and repeating the actions of another otter. However, only the otters species that hunt together in the wild are able to learn from others.

Scientists from the University of Exeter gave otters sets of food-baited puzzles to solve. The experiments were conducted in captivity, at zoos and wildlife parks. The otters were given plastic Tupperware containers with clips on the lids, screw-top lids, or pull off lids. Inside were treats such as peanuts and fish heads. The most difficult task? A block of frozen shrimp attached to a bamboo stick — it had to be moved up and to the right to get it out of the plastic container. Only half of the otters managed to get the shrimp out.

Smooth-coated otters learn from each other, especially when they are young. Image credits: Kokhuitan.

“Social learning has been studied in many species, but never in otters,” said Dr. Neeltje Boogert, of the Centre for Ecology and Conservation at the University of Exeter’s Penryn Campus in Cornwall.

Young otters copied their parents to solve the puzzles: the offspring solved the puzzles much faster than their parents. However, not every otter species did this. Smooth-coated otters copied their parents, while Asian short-clawed otters did not. The researchers expected to find social learning in both otter species, so it was surprising that the Asian short-clawed otter didn’t exhibit it.

“Asian short-clawed otters are not known to forage in groups, and their natural diet consists mainly of prey such as shellfish and crabs that do not require group-hunting strategies. As a result, they may have less of a tendency to turn to each other to see how to solve a puzzle such as how to extract food from a new source. In the wild, smooth-coated otters show coordinated group-hunting strategies such as V-shaped swimming formations to catch fish — so it makes sense that they would be naturally inclined to watch each other for foraging information,” explained Dr. Boogert.

This finding is cool, but it is also practical. Many otters are endangered in the wild, so captive breeding programs and re-release are used to help them recover. Previous work on captive breeding and re-release has found that animals with wild skills, like catching food (or cracking open sea urchins with rocks) and avoiding predators, have a higher rate of survival. Teaching the otters certain behaviors through social learning can help them to survive in the wild.

Journal reference: Zosia Ladds, William Hoppitt, Neeltje J. Boogert. Social learning in ottersRoyal Society Open Science, 2017; 4 (8): 170489 DOI: 1098/rsos.170489