Most of the time, female elephant seals are fishing in darkness. Scientists have figured out how sleek swimmers locate their prey by attaching cameras to their heads.
The research on sea lions in captivity has come to the same conclusions as this one. Grant says that the new work shows how seals use their whiskers in the wild.
Five northern elephant seals were included in the new study. They were fitted with cameras about the size of flash drives, as well as small sensors that detect light, depth, and open and closed mouths. When the animals left the shore for a 2-month ocean migration in search of food, the data was recorded by the team. Scientists collected the devices and analyzed the footage when the seals came back to shore.
The seals kept their whiskers out of the water at the beginning of each dive. They extended their whiskers as they entered the dark waters. At even deeper depths, where their favorite meals of squids and lantern fish reside, the seals constantly moved their whiskers back and forth like a dish antenna scanning for a signal.
Daniel Costa, a marine Biologist at the University of California, Santa Cruz, has been studying elephant seals for more than 40 years.
According to lead author Taiki Adachi, cats and rats use whiskers to sense air flow, but seals use their flippers to sense water flow.
According to co-author Rachel Holser, researchers in the field are used to seeing seals using their whiskers to investigate backpacks and other gear people leave on the ground. She and her colleagues were not expecting to see the coordinated and rhythmic movement of the animals' whiskers.
The researchers think the seal whiskers may be able to detect the currents caused by the fish swimming, as well as tiny movements in the water. The harbor seals have been shown to be able to track a herring swimming as far as 180 meters away. Seven times more nerve fibers are found in seals than in mice.
Dehnhardt isn't impressed by the results. The seals use their whiskers to follow water tracks, according to his work with them. The researchers only presented footage of the seals moving their whiskers close to fish, and they did not link these movements to the water currents left by the prey.
Grant is still being hit over the head. The study shows the range of adaptations animals need to survive in dark waters. She notes that toothed whales, which also fish the deep waters, developed echolocation, using sounds to "see" in the dark, while seals developed an alternative strategy that's common across land mammals. She says thatWhisking evolved among mammals. It's important to see it in seals as we're only starting to understand the importance of whisker movements.
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