Successful hunt in the dark of the seas

uAmong mammals, we humans are exotic in many respects – including when it comes to how we explore our immediate surroundings: that’s where we use our fingertips, and that’s extremely rare in the animal kingdom from marsupials to monkeys. Instead, the sense of touch in most animals is based on special whiskers, also called vibrissae. Nerve fibers that react to movements end in their hair follicles. With muscles attached to the hair follicle, the whiskers on the snout can often also move actively to explore the environment.

Sea lion Lo as test subject

Seals are not only equipped with particularly stately moustaches. With hair follicles, in which about ten times as many nerve fibers end as in cats or mice, their whiskers react correspondingly more sensitively. Scientists led by Alyx Milne from Manchester Metropolitan University and Charlotte Black from Blackpool Zoo studied how well spatial structures can be felt with it. The researchers’ subject was a female California sea lion named Lo, trained for years to perform small tricks in exchange for a tasty bite of fish.

Blindfolded and filmed with video cameras, the female sea lion was asked to choose the right one from among three fish dummies of different shapes or textures. Once she learned which type of shad offered a nutritious reward, Lo performed brilliantly, almost always making the right choice. It took her no more than a second to make her decision, as Milne and her colleagues report in the Journal of Experimental Biology.

The decision-making process took the longest when the sea lion had to choose between different sizes. Finally, Lo also had to scan the edges of the presented objects. She didn’t have to move her head and whiskers as extensively to find the right texture. Apparently, California sea lions can adjust their probing touch to suit their needs, much like humans adjust their finger movements.

Diving to depths of more than a thousand meters

How elephant seals use their mustaches to spot and catch their prey in the dark has recently been discovered by marine researchers from Japan and the United States. In search of fish and squid, these imposing seals dive several hundred, sometimes even more than a thousand meters deep. There is nothing to see down there apart from the flares emitted by some deep-sea creatures.

The research subjects were adult female northern elephant seals who had raised their young on the beach at Año Nuevo State Park in California. When the female elephant seals come ashore there in January or February, a long fast begins for them: they give birth to their offspring, nurse them for four weeks and then mate again. They then spend two months on the high seas. There they try to replenish their depleted fat reserves before returning to land for their annual moult.