A team led by Robyn Grant from Manchester Metropolitan University studied three different pinniped species’ whiskers: the California sea lions, Harbor seals, and Pacific walruses.
The purpose was to measure whisker movements and control in those species and compare them with terrestrial species such as rats and shrews. When it comes to whiskers, those two are considered specialists, moving their long facial hairs always, back-and-forth up to eight times a second.
The results were impressive. The three marine mammalians seem to be whiskers specialists too. Their whiskers are a part of a sensory system that helps them explore, forage, hunt, and navigate. They have the same importance as they do for terrestrial animals.
The pinniped’s vibrissae (whiskers) have ten times the innervation of terrestrial mammals, allowing them to detect vibrations in the water effectively. Detecting waves helps them foraging and may even replace vision, particularly in darkness.
Harbor seals have been observed to discriminate fish species and their size with the help of their whiskers. Blind ringed seals have also been observed successfully hunting, relying on their vibrissae to gain sensory information and catch prey.
The new study shed more light on how sea lions, seals, and walruses use their whiskers
It was thought that pinnipeds don’t move their whiskers over an object when examining it. They extend their moveable whiskers and keep them in the same position maximizing their detection ability. The new study gives reason to think differently.
“Now that we’ve learned that sea lions move their whiskers the most and can orient the most to contact, we want to see if they are capable of task-specific whisker movement – using their whiskers much like we move our fingertips,” says Grant.
Walruses have the most vibrissae, at 600–700 individual hairs. These are important for detecting their prey on the muddy seafloor. In addition to foraging, vibrissae may also play a role in navigation. Spotted seals appear to use them to identify breathing holes in the ice.
When allured by balancing food in front of their face, all three marine mammals pointed not just their heads but their whiskers too toward the fish. More than that, the walrus engaged in head-turning asymmetry. That means that the whiskers moved ahead of the head rotation to scan the area that the head is moving into.
Also, the walrus and sea lion engaged in contact-induced asymmetry, meaning that their whiskers were positioned asymmetrically toward an object. Both head-turning asymmetry and contact-induced asymmetry are features common for terrestrial mammals. Well, not anymore!