It remains a mystery why otters have a favorite stone that they keep throughout their lives. Biologists continue to speculate on an explanation.
Otters have a favorite stone that they keep for their entire life
According to Susan Milius, a specialist in Life Sciences, the idea that otters juggle stones is a media hype. Her argument to Science News is the following: the movement they make is more similar to a swinging motion between the front legs, than to an exercise of rhythmically throwing objects into the air.
Although this American author has a point, it is a fact that otters carry a stone with them all their lives: they choose the one they like best and keep it with them forever.
According to the same specialist, this has to do with a kind of game that trains them for the challenges of the environment, in which they encounter threats and opportunities for survival every day.
It is recorded that the movements that otters make with their favorite stone are very close to the chest, almost as if they were rolling it over the surface of their bodies.
In the wild, small-clawed animals such as otters need to hone their skills to peel mollusks, extract crustaceans from their shells, or open the shells of other prey for food.
The oscillatory movement that these animals make with the stones could be explained in this way: as an evolutionary need to adapt to their environment, in which they have to keep their nails sharp.
However, this is just one more speculation among many. According to biologist Mari-Lisa Allison, there is insufficient empirical evidence to support this claim.
This was the conclusion of a study she conducted with her team, in which the behavior of wild and captive otters was closely observed.
According to evolutionary theory, in the animal world, play does not have a practical function, nor does it satisfy an immediate need for survival. Moreover, it has been observed that otters continue this behavior regardless of their age: both young and older specimens do it.
This is why Gordon Burghardt, a researcher at the University of Tennessee, concludes that otters probably do it “just for fun, because they are bored, or for both reasons”.