Some marine mammals have whiskers that can detect turbulent fish waves. How this process works at various distances is the subject of a new experiment.
Harbor seals use their whiskers to track their prey in murky coastal waters where visibility is low. These thick, long bristles are sensitive to turbulence caused by fish in the area. Most attempts to understand this perception have focused on situations where the predator is just behind its prey and follows it from a distance. This phenomenon has now been investigated experimentally by Pengyao Gong and colleagues at the University of Texas at Dallas for various distances and orientations between the two animals.
A fish's movement through the water causes its skin to form eddies, which leave a turbulent trail behind them. These eddies have been shown to cause what is known as wake-induced vibration (WIV) in a seal's whiskers.
Gong et al. conducted an experimental study on this phenomenon. They replaced the fish with a vertical cylinder that moves horizontally and the whisker with a much thinner rod fixed at one end. The researchers found that most of the time the power of the WIV decreases as the cylinder-to-whisker distance increases. However, in an experiment designed to simulate a sudden increase in the speed of a fish, the cylinder was pushed extremely quickly, resulting in a slower WIV decline due to the larger eddies created by the faster movement of the cylinder.
The scientists also discovered that whisker oscillations were sensitive to the relative positions of the whisker and rudder: when the two were not in line, the rudder still caused whisker vibrations, but the balance position of the vibrations changed. According to the researchers, the findings of the study show that a seal's whiskers can carry a lot of information about the speed and direction of its prey.
Source: physics.aps.org/articles/v16/s46
📩 24/03/2023 19:50