When they are born, young bottlenose dolphins have two thin rows of whiskers along their beak-shaped snout, similar to the touch-sensitive whiskers of seals. However, these whiskers fall off shortly after birth, leaving the calves with a series of dimples known as vibrissal crypts. Recently, Tim Huttner and Guido Dehnhardt from the University of Rostock in Germany began to suspect that these crypts might be more than a mere remnant.
As published in the Journal of Experimental Biology, researchers suggest that these dimples may enable adult bottlenose dolphins to perceive weak electric fields, aiding them in navigating the underwater world. Upon closer examination, scientists noticed that the residual dimples resemble the structures that allow sharks to detect electric fields. When they tested captive dolphins to determine if they could sense an electric field in water, all the animals demonstrated an ability to detect the field.
“It was really impressive to see,” said Dehnhardt. To gauge the sensitivity of bottlenose dolphins to electric fields produced by aquatic life, Dehnhardt and Huttner collaborated with Lorenzo von Fersen from the Nuremberg Zoo and Lars Miersch from the University of Rostock. The team first tested the sensitivity of two dolphins, Donna and Dolly, to different electric fields to find out if dolphins could detect a fish buried in the sandy bottom.
After training each animal to rest their jaw on a submerged metal bar, Huttner, along with Armin Fritz from the Nuremberg Zoo and other colleagues, taught the dolphins to swim away within 5 seconds upon perceiving an electric field produced by electrodes placed just above the dolphin’s snout.
Gradually decreasing the electric field from 500 to 2V/cm, the research team tracked the number of times the dolphins swam away, staying impressed: Donna and Dolly were equally sensitive to stronger fields, correctly moving away almost every time. Only when the electric fields became weaker did it emerge that Donna was slightly more sensitive, perceiving fields of 2.4V/cm, while Dolly noticed fields of 5.5V/cm. However, electric fields produced by living animals are not static.