Petra Stock
Bottlenose dolphins can sense electricity underwater with the help of their dimples, and their detection skills are on par with platypus.
Baby dolphins are born with whiskers, which fall out, leaving dimples. Researchers from Germany’s University of Rostock and Nuremberg Zoo thought these features appeared similar to structures in sharks which allow the ocean predators to sense electricity.
The researchers tested the electric sensing abilities of two dolphins in captivity – Donna and Dolly – finding the animals capable of detecting extremely weak electric fields. Their research is published in the Journal of Experimental Biology,
After training the bottlenose dolphins (Turnips truncates) to wait at an underwater station, and swim away within 5 seconds of sensing an electric field, the researchers gauged their sensitivity to fields ranging from 500 to 2 microvolts per metre, μV/cm. A cuttlefish has a bioelectric potential of 10-30 μV.
The duo responded to extremely weak electric fields, although Donna (2.4 μV/cm) was slightly more sensitive than Dolly (5.5 μV/cm). The low threshold places the dolphins’ electric sensing skills at a level comparable to a platypus.
The researchers also trialled the dolphins’ ability to detect electric pulses, in alternating current. Donna and Dolly were again able to detect these signals, albeit at a higher threshold than for direct current.
The experiments were carried out once a day, 5 days a week. During these sessions the animals received a fifth of their daily diet in herring, sprat and squid. The study notes Donna and Dolly were “not subject to pain, suffering or injury”.
The ability to sense weak electric fields is exclusive to underwater, or semi-aquatic creatures. In another species, Guiana dolphins (Sotalia guianensis), the ability has been linked to foraging, helping them detect bottom-dwelling fish.
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The Ultramarine project – focussing on research and innovation in our marine environments – is supported by Minderoo Foundation.