Born with two rows of whiskers on their snouts, bottlenose dolphin calves lose these whiskers shortly after birth, leaving behind vibrissal pits. Initially believed to be mere remnants, these pits have now been identified as possibly integral to the dolphin's newfound electric sense. Dehnhardt noted, "It was very impressive to see," as they observed captive bottlenose dolphins reacting to electric fields in water. This observation, set to be published in the Journal of Experimental Biology on November 30, 2023, suggests a significant parallel with the electrosensitive structures found in sharks.
The research team, including Lorenzo von Fersen at Nuremberg Zoo and Lars Miersch from the University of Rostock, conducted experiments to gauge how sensitive dolphins are to the electric fields produced by other life forms in water. The study involved two dolphins, Donna and Dolly, and focused on detecting a fish buried in sandy sea floors. By training these dolphins to respond to electric fields, the researchers found that Donna could sense fields as weak as 2.4uV/cm, while Dolly detected fields of 5.5uV/cm.
Further tests revealed that the dolphins could also sense pulsating electric fields, although with less sensitivity compared to steady fields. This ability could be crucial for locating prey, as the movement of fish gills causes fluctuations in their electric fields.
Dehnhardt highlighted the practical implications of this discovery, stating, "The sensitivity to weak electric fields helps a dolphin search for fish hidden in sediment over the last few centimeters before snapping them up." This finding contrasts with the abilities of sharks, known as electrosensitive superstars, which can detect electric fields of prey from distances of 30-70cm.
Interestingly, Huttner and Dehnhardt also propose that this electric sense could aid dolphins in large-scale navigation. As dolphins swim through the Earth's magnetic field, they might generate detectable electric fields across their bodies, potentially allowing them to navigate globally using a magnetic map. Dehnhardt explains that dolphins moving at a normal speed of 10m/s could generate an electric field of 2.5uV/cm, enhancing their navigational abilities.
This discovery not only adds a new dimension to our understanding of dolphin biology but also sheds light on the complex sensory world of marine mammals. Traditionally recognized for their echolocation, hearing, and vision, dolphins' potential ability to detect electric fields opens up new avenues for research and understanding of marine mammal behavior and ecology.
Research Report:Passive electroreception in bottlenose dolphins (Tursiops truncatus): implication for micro- and large-scale orientation
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University of Rostock
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