Introduction: How Do Seals Swim So Smoothly in Cloudy Water?
Swimming in murky or cloudy water is challenging for humans because visibility drops to just a few centimeters. However, harbor seals (Phoca vitulina) effortlessly glide through turbid coastal waters with remarkable ease. Scientists have long understood that seals rely heavily on their sensitive whiskers and other senses to perceive their surroundings. But new research now reveals that vision plays a crucial and surprising role in seal navigation—even in low-visibility underwater environments.
New Research on Seal Vision and Marine Navigation
A recent groundbreaking study published in the Journal of Experimental Biology uncovers how harbor seals use optic flow—the visual perception of motion caused by particles and objects moving past their eyes—to determine their direction of movement in cloudy waters. This discovery could significantly advance our understanding of marine animal behavior and underwater navigation.
What Is Optic Flow and Why Is It Important for Seals?
Optic flow refers to the pattern of apparent motion experienced by an observer when moving through a fluid environment. For seals swimming through turbid water filled with suspended particles, detecting optic flow can provide essential visual cues to understand their heading and movement.
How Scientists Tested Seal Navigation Using a Unique “Video Game” Setup
Dr. Frederike Hanke and her team from the University of Rostock, Germany, teamed up with Markus Lappe from the University of Münster to test whether harbor seals could interpret optic flow for directional navigation.
The Experiment Setup:
- Three computer simulations mimicked different underwater environments:
- Open Water Simulation: Dots streaming outward, simulating forward swimming.
- Seabed Simulation: Dots moving below, mimicking the ocean floor.
- Surface Water Simulation: Dots moving above, like the water surface passing by.
- Three harbor seals—Nick, Luca, and Miro—were trained to watch the moving dots on the screen and indicate whether they felt their direction was turning left or right by tapping a red ball beside them.
- Correct answers were rewarded with sprats, a favorite fish treat, encouraging motivation and engagement.
Key Findings: Harbor Seals Reliably Use Visual Cues to Navigate
The dot patterns varied subtly in angle from 2° up to 22°, left and right. Despite natural distractions and varying motivation, all three seals showed a strong ability to detect their swimming direction from optic flow cues alone.
Highlights:
- Seals accurately interpreted particle motion to determine their heading.
- Vision plays a significant role even when water clarity is poor.
- This ability likely helps seals estimate distance traveled and supports spatial navigation in the wild.
Implications for Marine Biology and Animal Cognition
This research reveals that harbor seals possess a highly adaptable visual system enabling them to navigate efficiently in turbid, low-light underwater environments. Dr. Hanke suggests that optic flow perception might be integral to seals’ ability to map routes and move confidently through their coastal habitats.
Understanding how seals use vision for underwater navigation could influence new developments in:
- Marine animal behavior studies
- Biomimetic designs for underwater robotics
- Conservation strategies for marine mammals
Conclusion: Vision Is a Vital Sense for Harbor Seal Navigation
This innovative “seal video game” experiment highlights that, contrary to previous assumptions, vision is a crucial sense for harbor seals swimming in murky waters. Harnessing optic flow, seals can perceive their movement direction with impressive precision, aiding their survival in challenging marine environments.
Reference
Sandow, L. M., Thimian, A.-K., Lappe, M., & Hanke, F. (2025). Optic flow, a rich source of optic information for harbour seals (Phoca vitulina). Journal of Experimental Biology. DOI: 10.1242/jeb.250168