Research suggests they can sense weak electric fields

Born tail first, small bottlenose dolphins emerge equipped with two thin rows of whiskers along their beak-like snouts, much like the tactile whiskers of seals. But the whiskers fall off soon after birth, leaving the young with a series of dimples called vibrissal pits. Recently, Tim Hüttner and Guido Dehnhardt of the University of Rostock, Germany, began to suspect that dimples might be more than just a relic.

Could they allow adult bottlenose dolphins to detect weak electric fields?

Upon closer inspection, they realized that the remaining pits resembled the structures that allow sharks to detect electric fields, and when they tested whether captive bottlenose dolphins could detect an electric field in water, all the animals smelled the field. “It was very impressive to see,” says Dehnhardt, who published this extraordinary discovery and how animals could use their electrical sense in the Journal of Experimental Biology.

To find out how sensitive bottlenose dolphins are to electric fields produced by life forms in the water, Dehnhardt and Hüttner teamed up with Lorenzo von Fersen of the Nuremberg Zoo and Lars Miersch of the University of Rostock. First, they tested the sensitivity of two bottlenose dolphins, Donna and Dolly, to different electric fields to find out if the dolphins could detect a fish buried in the sandy sea floor.

After training each animal to rest its jaw on a submerged metal bar, Hüttner, Armin Fritz (Nuremberg Zoo) and an army of colleagues taught the dolphins to swim within 5 seconds of immediately feeling an electric field produced by electrodes. above the dolphin’s snout. .

By gradually decreasing the electric field from 500 to 2 μV/cm, the team tracked how often the dolphins departed at the right time and were impressed; Donna and Dolly were also sensitive to the strongest fields, coming out correctly almost every time. Only when the electric fields became weaker did it become apparent that Donna was slightly more sensitive, detecting fields of 2.4 μV/cm, while Dolly became aware of fields of 5.5 μV /cm.

However, electric fields produced by living animals are not just static. The pulsing movements of fish’s gills cause their electric fields to fluctuate, so could Donna and Dolly also detect the pulsing fields? This time, the team pulsed the electric fields 1, 5, and 25 times per second while reducing the field intensity, and sure enough, the dolphins were able to detect the fields.

However, none of the animals were as sensitive to alternating fields as to invariable electric fields. Dolly was only able to sense the slowest field at 28.9 μV/cm, while Donna was able to sense all three oscillating fields, detecting the slowest at 11.7 μV/cm.

So, what does this new super sense actually mean for dolphins? Dehnhardt explains: “Sensitivity to weak electric fields helps dolphins search for fish hidden in the sediment in the last few centimeters before catching them,” unlike sharks, electrosensitive superstars, which are able to detect the electric fields of fish at the interior. 30 to 70 cm. Hüttner and Dehnhardt also suspect that the dolphin’s ability to sense electricity could help them on a larger scale.

“This sensory ability can also be used to explain the orientation of toothed whales relative to the Earth’s magnetic field,” says Dehnhardt, explaining that dolphins swim in weak areas of the Earth’s magnetic field at a normal speed of 10 m/s could generate a detectable electrical current. field of 2.5 μV/cm across their body. And if animals swim faster, they are even more likely to detect the planet’s magnetic field, allowing them to use their electrical sense to navigate the globe using a magnetic map.