The dark ocean limits most animals in their abilities to detect prey and many species have come up with ingenious ways to find food down in the deep. Whales, for example, use echolocation, while some fish use light to reel in prey. What seals were up to in the deep ocean has been a secret for a long time as the natural movement of the species is hard to observe.
A team of researchers from the University of California in Santa Cruz has now found evidence for seals using their whiskers in the deep, dark ocean by analysing footage from cameras with infrared night-vision that were attached to the animals as part of the study. “Based on direct observations, we show how deep-diving seals locate their prey without the biosonar used by whales, revealing another mammalian adaptation to complete darkness,” the study reads.
The research team decided to attach the cameras to the left cheek, lower jaw, back and head of five northern elephant seals in California’s Año Nuevo state park. Through this approach, they were able to collect nine and a half hours of video footage, revealing what the seals did in the deep sea.
After analysing the videos, the research team established that the five seals held back their whiskers during the first part of their dives, while their whiskers “extended forward ahead of the mouth” and started to rhythmically move back and forth as soon as they reached a depth suitable for finding food. The team found that the mammals used their whiskers to sense vibration in the water that was caused by swimming prey. When the seals returned to the surface, they curled their whiskers back up.
The videos also showed that bioluminescence emitted by prey only contributed to around 20% of overall foraging success – a clear indicator that the elephant seals primarily use their whiskers to sense prey in the deep ocean.
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Photography courtesy of Unsplash.