Washington: Hunting in the North Sea, harbour seals often encounter murky water that impedes their vision. So it is important that they have another method to chase their prey.
Now, a new study has suggested that these mammals are able to identify the size and shape of their prey using only their vibration-sensitive whiskers.
Wolf Hanke and his colleagues from the University of Rostock, Germany, had earlier found that seals could pick up and follow fish wakes up to 35 seconds after the prey has passed.
Knowing that a fish`s size and shape can dramatically affect its wake structure, graduate student Sven Wieskotten then decided to find out how well seals can distinguish between the wakes of objects with different shapes and sizes.
Teaming up with Henry the harbour seal at the Marine Science Centre, Germany, the researchers began testing Henry`s ability to distinguish between the wakes of differently sized paddles.
They blindfolded Henry and covered his ears, then they swept a paddle through a large box in Henry`s enclosure and allowed him to enter it 3 seconds later.
The team found that Henry could distinguish between paddles that differed by as little as 2.8cm in width.
Next, the team varied the paddle shapes and asked Henry to distinguish between the wakes of triangular, cylindrical, flat and undulating paddles.
The seal successfully distinguished between the flat and cylindrical paddles, the flat and undulating paddles and the undulating and cylindrical paddles after they were swept through the enclosure.
However, he had problems distinguishing the triangular paddle from the undulating or cylindrical shapes.
The findings were published in The Journal of Experimental Biology.