Wiggling Whiskers Help Hungry Seals Hunt in the Dark

Wiggling Whiskers Help Hungry Seals Hunt in the Dark

A new seals’-eye view shows these specialized hairs in motion at sea

Northern Elephant Seal (Mirounga angustirostris). A puppy learning to swim after being weaned. Credit: Francois Gohier/Science Source

Scientists have long wondered how deep-diving seals eat in pitch-black waters. The answer may be right under their noses: whiskers. With the help of a group of northern elephant seals in California’s Ano Nuevo State Park, researchers have now seen this super specialized sensory system at work in the wild for the first time.

By gluing tiny cameras, each about as big as a snack-size candy bar, to the seals’ left cheeks, researchers at the University of California, Santa Cruz, and their colleagues recorded more than nine hours of footage of the animals’ long, flexible whisker hairs in motion while they dove for their dinner. Researchers used trackers to measure how far and deep animals traveled in previous studies of wild marine mammals. But this time scientists built cameras systems small enough to record actual footage of seals’ deep dives without getting in their way. The first-of-its-kind video footage used in the team’s new study, published on Monday in Proceedings of the National Academy of Sciences USA, is a big step forward in understanding how seals hunt rather than just where they go.

Seals in captivity have shown they can hunt with whiskers alone when blindfolded, so researchers had long suspected that this sensory system might be the key to the animals’ knack for low-light foraging. “But in nature, animals will combine all information from multiple sensory systems to form behavior in the wild U.C. says that they can use their eyes, whiskers, or hearing. The study’s lead author is Taiki Adachi, a Santa Cruz marine ecologist. “We ensure that seals actively use whiskers deep ocean .”

The area where each whisker meets the seal’s face is surrounded with nerve endings. This makes this array of specialized hairs extremely sensitive to small changes in water flow. Adachi and his colleagues observed the foraging seals move their whiskers with muscles in the snout, a motion known as “whisking”, and in patterns similar to those used by mice and rats to explore land. Researchers only observed this behavior when the seals were at their hunting depths. This suggests that the animals were using their whiskers for water exploration. The seals kept their whiskers against their heads when they weren’t eating. When the animals were ready for their next meal, their whiskers would kick into action.

A deep-diving seal’s whiskers move during a hunt for fish in the dark. Credit: “Whiskers as Hydrodynamic Prey Sensors in Foraging Seals,” by Taiki Adachi et al., in Proceedings of the National Academy of Sciences USA, Vol. 119. Published online June 13, 2022

” We don’t have a facial hair that we can move so it’s difficult to imagine how seals sense the world with their whiskers,” Adachi said. Adachi says, “We see the globe the same way we see it; elephant seals see it differently.” Adachi and his team also examined the camera footage to determine if any bioluminescent prey was visible. Researchers found that seals caught in bright bioluminescent glows only one out of five times, which confirmed that the animals were not relying solely on their eyes. Whisker movement was most likely a primary role.

” These field studies are really needed,” said Guido Dehnhardt (a marine scientist at University of Rostock in Germany), who has done many years of experiments to monitor whiskers in captive seals. He was not involved with the new study. “It is a huge challenge to do this in the wild with free range animals. The results are really impressive.” Dehnhardt warns that only video of whiskers does not show that they respond to changes in water motion. Future experiments will ideally measure both the whisker movements and the surrounding water flow simultaneously. These data could be a great help in understanding how seals depend on whiskers to ensure their submarine snacking success.

ABOUT THE AUTHOR(S)

    Sasha Warren is a 2022 AAAS Mass Media Fellow at Scientific American. They are curren

    Read More