Whisker-borne dolphins possess an unusual ability

Investigators have established that dolphins possess an unusual extra sense. They can detect electric fields, a capability bestowed upon them by their birth whiskers, or to be precise, the remnants of the whiskers' locations.

Likened to seals, bottlenose dolphins are birthed with two rows of whiskers which disappear soon after, leaving behind noticeable indentations. According to scientists from the University of Rostock, these indentations might play a crucial role in the dolphins' existence, asserting that this feature probably enables them to perceive weak electric fields.

The researchers observed that the dolphin's indentations mirror the shark's structures, which are accountable for their ability to detect electric fields. Hence, a selection of experiments revealed that dolphins are indeed capable of sensing electric fields.

Scientists conducted several experiments with two bottlenose dolphins named Donna and Dolly to test this theory. They methodically trained them to hover next to a submerged metal rod and swim away within a rapid 5 seconds once an electric field was activated by electrodes situated near their snouts. This experiment was carried out using diverse strengths of electric fields ranging from 500 to 2 µV/cm. Both dolphins reacted similarly to the most potent field, but with lower intensities, the responses varied - Donna could detect an intensity of 2.4 µV/cm, whereas Dolly could sense 5.5 µV/cm.

Scientists, however, pointed out that fields generated by living species are non-static. As an illustration, the field produced by the undulating gills of a fish experiences regular fluctuations.

To test the dolphins' capacity to respond to such dynamic fields, the researchers generated a pulsating field, fluctuating between 1.5 and 25 times per second while sequentially reducing its strength. Donna and Dolly were both able to perceive the changing field, although their sensitivity was more attuned to a static field. Dolly detected the more extended waves at an intensity just below 30 µV/cm, and Donna at 11.7 µV/cm.

How does this affect dolphins? Researchers believe that the ability to sense weak electric fields empowers dolphins to locate fish concealed in the ocean floor's sand up to a few centimeters. For comparison, proficient responders to electric fields, like sharks, can detect fish concealed in the sand even at depths of 70 cm.

Alternatively, the ability to detect electric fields might serve another purpose. "This could elucidate the ability of toothed whales - inclusive of dolphins - to orient themselves corresponding to the Earth's magnetic field," according to Professor Dehnhardt.

Accordingly, dolphins that swim at speeds of 10 m/s (about 22 mph) can generate a weak yet detectable electric field when aligned with the Earth's magnetic field, the research team calculated. When they swim faster, the field becomes progressively stronger.