Whisker Shape and Orientation Help Seals and Sea Lions Minimize Self-Noise

While it doesn’t always pay to take the path of least resistance, sometimes it’s best to just go with the flow. New research on seal and sea lion whiskers help explain how they are adapted to do just that.

Whiskers, more technically known as vibrissae, provide their owners with important sensory information about the world around them. The follicle of each whisker is connected to many nerves, allowing an animal to “feel” its surroundings by picking up tiny vibrations in air or water. Sea lions (pictured left) and seals (right), like land mammals, are equipped with a highly sensitive array of whiskers that allows them to detect disturbances from afar or zero in on the wake of their next meal. A new study published in PLOS ONE explores the characteristics of seal and sea lion whiskers that make them particularly well-suited to underwater signal detection.

Researchers at the University of Florida investigated the hydrodynamic properties — the natural properties of liquids in motion — of whiskers from three different pinniped species: harbor seals, northern elephant seals, and California sea lions. Using CT scanning, researchers precisely measured the shape of each species’ whiskers.  While the cross sections of whiskers in land mammals are almost perfectly circular, seal and sea lion whiskers are somewhat flattened, in the shape of an oval. In this study, the researchers ran water currents over the pinniped whiskers at different angles, watched how the whiskers responded, and, measured the amount of whisker vibration at different orientations relative to the current.

The orientation of the whiskers, it turns out, affects how much they vibrate. The authors found that when the skinny edge of the whisker angled into the flow of water, the whisker vibrated far less than when the flat side faced the current.

The authors suggest that the flat shape of each whisker and its resting orientation — specifically, skinny side angled into the flow of water — may minimize the amount of self-induced whisker vibration generated by normal, forward swimming (video). The reduced base-level “whisker noise” may help whiskered marine mammals better detect important vibrations in the water, caused by the environment and nearby animals. And that, really, is what the whiskers are there for in the first place.

Citation: Murphy CT, Eberhardt WC, Calhoun BH, Mann KA, et al. (2013) Effect of Angle on Flow-Induced Vibrations of Pinniped Vibrissae. PLoS ONE 8(7): e69872. doi:10.1371/journal.pone.0069872

Image: Image comes from Figure 5 of the manuscript