Have you ever looked at a seal or a sea lion and wondered about their voluptuous whiskers? Those fine hairs, called whiskers or vibrissae, have a crucial role in their lives. Studies have shown that blindfolded captive harbor seals (Phoca vitulina) can easily follow other seals underwater, using only their whiskers. Yet, that was just the tip of the iceberg; what do these whiskers really do?
When do seals use their whiskers?
All pinnipeds (seals, sea lions, fur seals, and walruses) have whiskers on the sides of their mouths. In the 1970s, researchers discovered that these specialized hairs are used to detect water movements. In a way, they are the seals’ sense of touch. Instead of feeling an actual physical touch (skin-on-skin), pinnipeds use their whiskers to sense little wakes in the water. It is similar to when humans detect the wind blowing on our skin.
Seals often look for food in murky waters. The Wadden Sea and Baltic Sea have high turbidity; suspended silt and sand obstruct the view underwater. Similarly, deep-diving seals like the Weddell seal will dive in search of food, so deep that the light from the surface no longer reaches its feeding zone. In these situations, relying on sight to find and chase down fish is not possible. Therefore these seals need very accurate and highly sensitive sensors – whiskers.
Seals can trail a fish using their whiskers
Imagine a scenario where a seal is swimming around looking for fish, but it is too murky or dark to see anything. As the seal swims around, it passes through multiple hydrodynamic trails left from fish that swam in the area. It is like walking in the woods and passing through numerous animal tracks. If you are trained, you can look for signs of a deer or a boar. Their trail will look like footprints on the ground or flattened paths in the grass with some droppings.
But how could you find a trail left by a fish in the water? As fish swim, they leave a wake (little waves in the water) behind them, similar to what boats create on a surface. They do so by moving their fins. Now imagine you are sitting in your kayak on a lake. When a ship passes by, you feel the wake of that boat. Even if you have not seen the ship, you can tell that something has passed by because your kayak starts to move, and you can feel the waves. Similarly, seal whiskers can detect the “waves” left by fish swimming in the water. So how sensitive the seal’s whiskers are?
Sensing a fish half a football stadium away
Let’s look at a study performed at The Marine Science Centre of the University of Rostock, Institute for Biosciences. They ran some experiments using an artificial paddle to create wakes and then asked their captive seals to detect it. The results showed that when the water was calm, seals could successfully “see” wakes from the artificial paddle up to 35 seconds after the paddle was moved. How does this translate to real-life situations? Picture a calm body of water, like a gulf; a fish of reasonable size can easily swim tens of meters in 35 seconds. This means that a seal, using their whiskers, can detect a fish that swam by when this fish is already half a football stadium away. Impressive, right? Let’s go beyond…
Telling fish species apart from their trail
The same team tested if seals could tell different fish apart (in their shape) just by sensing their wake trail in the water? The results were impressive. The seals studied at the Centre were able to tell apart wakes created by paddles of different sizes and distinguish between differently shaped paddles, i.e., flat, cylindrical, triangular, or undulated paddles of the same width. In plain English, that means that seals could, potentially, recognize a species and size of the fish just by sensing its wake trail in the water. How insane is this?
So, do whiskers allow a seal to actually follow fish?
This experiment was the first one the Rostock team performed. They asked one of their seals to follow a wake trail created by other seals, while blindfolded and with earcups on so that the animal couldn’t rely on sight or sound. In this study, the results showed that the seal could stay entirely in the middle of the wake trail created by another seal, even though it was as wide as 2 m (6ft).
So yes, a seal can detect, identify, and follow a fish in murky, dark water. If you think that is awesome and incredible. I agree with you; it is 100% great! According to the lead scientist of these studies, Dr. Wolf Hanke, seals’ whiskers compare well with whales’ and dolphins’ echolocation performance. This ability, in itself, seems like a supernatural power.
What about fish that hide in the sand like flatfish?
Seals and their whiskers have more tricks “up their sleeves.” In coastal areas, fish use rocks and sand to hide from predators like seals. Some fish will hide in deep crevasses, some will use camouflage, and some will bury themselves in the sand like flatfish. For harbor seals, flatfish constitute up to 70 % of their diet. Flatfish skin acts as camouflage, to the point that they are almost impossible to spot. Yet, like all other fish, flatfish need to breathe. Even when they are buried in the sand, they still pump water through their gills and create tiny vortices or mini-jets of expelled water around them. The Rostock team put their seals to the test and found that they can detect those small jets of water. This means that seals are, actually, able to locate the flatfish buried in the sand. Bad news for flatfish!
We are only just discovering these and other extraordinary abilities of marine mammals. We can be sure there will be plenty more surprising facts uncovered in the years to come.
Sources & further reading:
- Dr. Wolf HAnke quote: https://www.bbc.com/news/10287564
- Wieskotten, S., et al. “Hydrodynamic determination of the moving direction of an artificial fin by a harbour seal (Phoca vitulina).” Journal of Experimental Biology 213.13 (2010): 2194-2200.
- Wieskotten, Sven, et al. “Hydrodynamic discrimination of wakes caused by objects of different size or shape in a harbour seal (Phoca vitulina).” Journal of Experimental Biology 214.11 (2011): 1922-1930.
- Schulte-Pelkum, N., et al. “Tracking of biogenic hydrodynamic trails in harbour seals (Phoca vitulina).” Journal of Experimental Biology 210.5 (2007): 781-787.
- Check out our other seal posts: https://whalescientists.com/tag/seals/
Marine biologist and animal trainer and behaviourist. I started my journey by studying marine biology at the University of Gdansk. Very quickly I got a chance to work in my dream job - marine mammal trainer at a marine station in the little town called Hel. From there it only got more interesting. I have worked for a number of zoos and facilities caring for seals and sea lions.
Recently, got involved with Ethoplanet - a consulting and education centre where I coordinate international relations as well as teach courses on animal training and welfare.
Currently, I am a keeper and trainer at Warsaw Zoo in Poland as well as a PhD student at Siedlce University of Natural Sciences and Humanities.
My interest focus on marine mammals and pinnipeds in particular. Their biology, ethology, ways of communication and primarily, their welfare under human care.