When in the deep, dark ocean, seals use their whiskers to track their prey, a study confirmed after observing marine mammals in their natural habitat.
It is difficult for light to penetrate the darkness of the ocean depths, and animals have invented various devices to live and hunt there. Whales and dolphins, for example, use echolocation, the art of sending 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 evolved to use other sensory techniques.
Scientists have long suggested that the secret weapons are their long, cat-like mustaches, conducting more than 20 years of experiments with artificial whiskers or captive seals blindfolded in a pool, given the difficulty of directly observing hunters in the dark depths of the ocean.
Now a study may have confirmed the hypothesis, according to Taiki Adachi, a research assistant at the University of California, Santa Cruz and one of the lead authors of the study, published in the Proceedings of the National Academy of Sciences. Adaci and his team deployed small infrared night-vision cameras on the left cheek, lower jaw, back and head of five wild northern elephant seals, Mirounga angustirostris, in Año Nuevo State Park in California. They recorded a total of about nine and a half hours of deep-sea footage during their seasonal migration.
Adachi and his team deployed small infrared night-vision cameras on the left cheek, lower jaw, back and head of five free-flowing northern elephant seals, Mirounga angustirostris, in Año Nuevo State Park in California. They recorded a total of about nine and a half hours of deep-sea footage during their seasonal migration.
Analyzing the videos, the researchers note that diving seals keep their whiskers at the beginning of their dives, and once they reach a depth suitable for foraging, they rhythmically swing their whiskers back and forth, hoping to feel every vibration caused by the most the small water movements of floating prey. (Elephant seals like to eat squid and fish and spend a long time at sea.) Then, as they swam back to the surface, their whiskers curled back to their faces.
In less than a quarter of the time seals have hunted, they can also see some bioluminescence – the light that some creatures can emit deep underwater thanks to chemicals in their bodies – to track their food with their eyesight. . But for the remaining 80% of their hunting activities, they probably only used their mustaches, according to Adaci. This technique is no different from rodents, Adachi notes. Simply because the water is much denser than the air, the breaking speed is much lower for elephant seals.
“That makes sense,” said Sasha Kate Hooker, a pinniped researcher in the Department of Marine Mammal Research at the University of St. Andrews, who was not involved in the study. “Among deep-sea marine mammals, the elephant seal reaches the same depths as sperm and beaked whales, often well over a kilometer below the surface.
Guido Denhardt, director of the Marina Science Center at the University of Rostock and a pioneer in mustache research who did not take part in the study, welcomed the findings but was cautious about how much new information they represented. “My group was the one that showed more than 20 years ago that seal mustaches are a hydrodynamic receptor system and that seals can use it, for example, to detect and track the hydrodynamic tracks of fish,” Denhard said.
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The study is particularly interesting from a technical point of view, especially with regard to the cameras used, which are so small, Denhard said, but there is still too much speculation. “It would be a great story if seals wore a hydrodynamic measuring system in addition to a head-mounted camera. [a machine that can measure the movement of fluids] so that mustache movements and hydrodynamic events can be correlated. “
Moving on, Adachi would like to begin comparing how other mammals use their whiskers to better understand how the superpower of some animals’ whiskers has shaped the animal kingdom’s eating habits.
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