Scientists have long been unaware of how deep-sea seals feed on their food in tar-black seas, and the answer may have been right under the animals’ noses all along: mustaches. With the help of a group of northern seal elephants in California Ano Nuevo State Parkresearchers have already seen this super specialized sensor system work in the wild for the first time.

By sticking small cameras, each as big as a candy, to the seals’ left cheeks, researchers at the University of California, Santa Cruz and colleagues recorded more than nine hours of long, lithe mustache hair on the move as they dived. for your dinner. In most such studies of wild marine mammals, researchers have used trackers that measure only how far the animals have traveled and how deep they have reached. But this time, scientists have built small enough camera systems capture real-life footage of deep seal dives without interfering with them. The first-of-its-kind video used in the team’s new study, published Monday in Proceedings of the National Academy of Sciences USAis a big step forward in understanding how seals hunt, not just where they go.

Captive seals have shown that they can only hunt with a mustache when they are blindfolded, so researchers have long suspected that this sensory system may be the key to animals’ ability to search for food in low light. “But under natural conditions, animals will use all the information from many sensory systems and integrate it to shape behavior in the wild … They can use eyes; can use a mustache; they can use hearing, ”said Uiki Santa Cruz marine ecologist Taiki Adachi, lead author of the study. “We make sure that seals are actively using mustaches in the deep ocean.”

The place where each mustache meets the seal’s face is surrounded by nerve endings, which makes this set of specialized hairs incredibly sensitive to minor changes in the nearby water flow. In the study, Adachi and his colleagues see feeding seals move their whiskers back and forth with muscles in their muzzles – a movement known as “swinging” – in models similar to those used by rats and mice to to explore on land. Researchers observed this behavior only after the seals were down to their usual hunting depths, suggesting that the animals used their whiskers to look for small waves of water caused by fish wagging their tails and swimming around. When the seals did not feed, they kept their whiskers pressed back to their heads. The mustache was triggered only when the animals were ready to feel their next feeding.

The mustache of a deep-sea seal moves while fishing in the dark. credit: “Whiskers as hydrodynamic sensors for prey in feeding seals”, by Taiki Adachi et al., In Proceedings of the National Academy of Sciences USAvolume 119. Published online on June 13, 2022

“We don’t have a mustache to move, so it’s very difficult to think about how seals feel about nature with their mustaches,” Adachi said. “We see the world as we see the world; Elephant seals see the world differently. “To study how seals’ senses work together to paint a picture of the immediate area, Adaci and his team not only observed the mustache – they also checked camera footage for visible bioluminescent prey that seals Researchers found that the bright bioluminescent glow was only matched by a successful seal hunt in one in five hunts, confirming that the animals did not rely solely on their eyes.

“These field studies are really urgently needed,” said Guido Denhard, a marine scientist at the University of Rostock in Germany who has conducted many years of experiments observing captive seals and did not participate in the new study. “Doing this in the wild with free-range animals is a real challenge – and the results are very impressive. Dehnhardt warns that the video of the mustache alone does not necessarily show that it is moving in response to changes in the movement of water around seals. Future experiments would ideally measure both the movement of the whiskers and the surrounding water flow. These data could go a long way to show how much seals rely on mustaches for their success with a submarine.

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