Seals use whiskers to track prey in deep seas, the study shows

When in the deep, dark sea, seals use their whiskers to track their prey, a study has confirmed after observing the marine mammals in their natural habitat.

It is difficult for light to penetrate the darkness in the depths of the sea, and animals have invented a variety of adaptations to be able to live and hunt there. Whales and dolphins, for example, use echolocation The art of emitting clicking sounds into the water and listening to their echoes as they bounce off possible prey, to locate them. But deep-sea seals that do not have the same acoustic projectors must have evolutionarily learned to use a different sensory technology.

Researchers have long assumed that the secret weapons are their long, cat-like whiskers, which conducted over 20 years of experiments with artificial whiskers or captured seals with blindfolds in a pool, given the difficulty of directly observing hunters in the thin depths of the sea.

Now, a study may have confirmed the hypothesis, according to Taiki Adachiassistant project researcher at the University of California, Santa Cruz, and one of the lead authors of study published i Proceedings of the National Academy of Science.

Adachi and his team placed small infrared video cameras on the left cheek, lower jaw, back and head of five free-ranging northern elephant sealsthe Mirounga angustirostris, in Año Nuevo State Park, California. They recorded a total of about nine and a half hours of deep-sea images during their seasonal migration.

Analyzing the videos, the researchers noted that diving seals held back their whiskers during the first part of their dive and, once they reached a depth suitable for foraging, they rhythmically whispered their whiskers back and forth in hopes of sensing vibrations caused by smallest water movements of swimming prey. (Seals like to talk about squid and fish and spend a long time out at sea.) Then, as they swam back to the surface, their whiskers bent back toward their faces again.

In less than a quarter of the time the seals hunted, they could also see some bioluminescence – the light that some creatures can emit deep underwater thanks to chemicals in their bodies – to track their meals using sight. But for the remaining 80% of their hunting trip, they probably only used whiskers, according to Adachi. This technology is no different from rodents, Adachi noted. It’s just that, because water is much denser than air, the whipping rate is much slower in elephant seals.

“This makes sense,” he said Sascha Kate Hooker, a pinniped researcher from the Sea Mammal Research Unit at the University of St Andrews, who was not involved in the study. “Among the deep-diving marine mammals, elephant seals reach the same depth as sperm and beaked whales, often well over a mile below the surface.”

Guido Dehnhardt, head of the Marina Science Center at the University of Rostock, and a pioneer in whisker research who were not involved in the research, welcomed the results but were careful about how much new information they represented. “It was my group that had shown more than 20 years ago that the seal’s whiskers represent a hydrodynamic receptor system, and that the seals can use it, for example, to detect and track the fish’s hydrodynamic traces,” said Dehnhardt.

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The study is particularly interesting from a technical point of view, especially given that the cameras used are so small, Dehnhardt said, but there is still too much speculation. “It would be a great story if the seals in addition to a head-mounted camera carried a hydrodynamic measuring system [a machine that can measure the movement of fluids] so that whisker movements and hydrodynamic events could be correlated. “

In the future, Adachi would like to start comparing how other mammals use their whiskers, to better understand how some animals’ whisker superpowers have shaped the animal kingdom’s foraging habits.

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