We know that marine creatures have finely tuned senses, but to be able to pinpoint from a distance a motionless, well-camouflaged flatfish in murky water through its breathing alone is sensitivity almost off the scale. That however is what researchers believe that harbour seals are able to achieve with the help of their whiskers.
A team of scientists from University of Rostock in Germany has just published the results of recent experiments in the Journal of Experimental Biology.
Flatfish feature in the diet of harbour seals, but because these fish make no noise the scientists wanted to test the hypothesis that the seals’ whiskers could detect the tiny currents created as water was emitted through the fishes’ gills.
They created an experimental platform in which an artificial breathing current was emitted into a pool through any one of eight nozzles.
Three seals were trained to search for whichever nozzle was active, and stay there for five seconds. Half of the trials were conducted with the seals blindfolded, but with or without their eye-masks their accuracy in detecting the current demonstrated that the results could not have been accidental.
Approaching the nozzles from different directions made no difference to the seals’ performances. They would respond to the currents by moving their snout straight towards the nozzle from which it came and proceeding in that direction.
The scientists believe the findings might explain why certain fish species suppress their breathing when disturbed.
They hope to follow up the experiment by testing how small a current a harbour seal can detect, and learning how it can distinguish the signal from “background noise”.
The report Hydrodynamic Detection and Localisation of Artificial Flatfish Breathing Currents by Harbour Seals (Phoca Vitulina) can be read here
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15-Feb-17
