Gaming Seals Use Cloudy Water to Navigate with Surprising Visual Skill.

Open-water swimming might seem disorienting to humans, especially in murky conditions where visibility drops to just a few centimeters. But for harbor seals (Phoca vitulina), the cloudy, coastal waters they inhabit pose little challenge. While they rely on several senses, including the sensitivity of their whiskers, researchers have now shown that vision also plays a crucial role in their underwater navigation.

Frederike Hanke from the University of Rostock in Germany set out to investigate whether harbor seals could interpret visual motion—specifically "optic flow fields," which are patterns of movement created on the retina as an animal moves through an environment filled with small particles. These subtle visual cues might help seals determine their heading, even in highly turbid water.

To test this idea, Hanke and her colleagues—Laura-Marie Sandow and Ann-Kathrin Thimian from the University of Rostock and Markus Lappe from the University of Münster—designed a creative experiment involving three seals: Nick, Luca, and Miro. The team developed a set of computer simulations to mimic underwater motion. The first simulation depicted the sensation of moving through open water with dots rushing forward. The second showed the seabed scrolling beneath the viewer, while the third simulated the water’s surface flowing above.

The seals were trained to sit in front of a large screen showing these dot patterns and indicate whether they felt they were moving left or right. They did this by tapping a red ball on the corresponding side of their heads—and were rewarded with a favorite treat, sprats.

Nick and Luca, already experienced with such tasks, adapted quickly. Miro, new to the process, took a bit longer to learn but soon caught on. "Miro is very open-minded and handled new situations well," Hanke noted.

The researchers varied the angle of the simulated direction—2, 6, 10, 14, 18, or 22 degrees to the left or right—and recorded the seals’ responses. Although occasional errors occurred, likely due to distraction or waning motivation, the results were clear: the seals could accurately detect their direction of movement based solely on the visual motion of particles in the simulated water.

“This shows that even in low-visibility conditions, harbor seals can rely on visual flow to navigate,” Hanke explained. The experiment demonstrated that seals perceive the motion of their surroundings much like how cloudy water, a shifting seabed, or the water’s surface would appear while they swim.

The findings, published in the Journal of Experimental Biology, suggest that harbor seals use more than just tactile senses to move with precision underwater. Hanke and her team now hope to explore whether these animals can also estimate the distance they've traveled using the same optic flow cues—a question that opens new doors into understanding animal navigation in aquatic environments.

Source:https://phys.org/news/2025-05-gaming-reveal-cloudy.html

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