It is well known that harbor seals use their whiskers to detect water velocities and the wakes of moving objects, and that these abilities help in capturing prey. But now German researchers have shown that a seal can also discriminate size and shape using only its whiskers.

The scientists used four paddles of different shapes and sizes to generate wakes in an experimental box submerged in a tank. The seal, a 12-year-old named Henry, was blindfolded and headphones were placed over his ears. He put his head into the tank to sense the size and shape of the paddle being used. The study was published on Thursday in The Journal of Experimental Biology.

When he successfully identified a size or shape by touching the paddle outside the box that corresponded to the one that had made the wake within, he was rewarded with a herring snack. The seal was eventually able to discriminate paddles differing in size by as little as 3.6 centimeters.

He was also able to distinguish shape — the flat from the cylindrical, the flat from the triangular and the flat from the undulated paddle. But he could not distinguish any other shape combinations.