Bottlenose dolphins are a highly researched marine mammal that has recently unveiled a hidden sixth sense. Researchers at the University of Rostock and Nuremberg Zoo in Germany have discovered that two captive bottlenose dolphins (Tursiops truncatus) possess the ability to consistently sense subtle electric fields in the water using their extended snouts.
During an aerial survey of marine mammals this small pod kindly posed for the camera.
Dolphins' Electric Sensory Secrets
The revelation raises the intriguing possibility that certain marine mammals possess the ability to detect the electrical signals emanating from small prey concealed in the sand. Furthermore, this heightened sensory capability might extend to discerning Earth's magnetic field, adding a layer of complexity to their sensory repertoire.
Notably, electroreception in placental mammals is a rare trait, with the Guiana dolphin being the only other documented species apart from bottlenose dolphins. A distinctive electroreception system was identified in Guiana dolphins, diverging significantly from that observed in fish, amphibians, and monotremes such as platypuses and echidnas.
In the new study, titled "Passive electroreception in bottlenose dolphins (Tursiops truncatus): implication for micro- and large-scale orientation Icon for The Forest of Biologists" published in the Journal of Experimental Biology, researchers conducted experiments involving bottlenose dolphins showcased their remarkable sensitivity to weak electric fields.
The study involved two captive bottlenose dolphins, Dolly and Donna, from Nuremberg Zoo. Although the findings provide valuable insights into their electroreceptive capabilities, further investigations are essential to comprehend how these dolphins utilize this sense in their natural environment.
Intriguingly, historical observations of 'crater feeding,' where bottlenose dolphins dive headfirst into the sand before swimming away with prey, suggest a potential role of electroreception alongside echolocation in their foraging strategy. This raises the prospect that electroreceptors may aid dolphins in locating hidden prey through the detection of electric fields generated by aquatic organisms.
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Dolphins Navigate Depths with Sensory Precision
To investigate the electric field sensitivity of bottlenose dolphins in response to aquatic life, researchers from Nuremberg Zoo and Lars Miersch at the University of Rostock trained two bottlenose dolphins. They conducted experiments where they discerned a fish hidden in the sandy sea floor by resting their jaws on a submerged metal bar.
The researchers systematically reduced the electric field strength from 500 to 2μV/cm, revealing consistent responses from both dolphins. As the fields weakened, Donna exhibited slightly higher sensitivity, detecting fields at 2.4μV/cm, while Dolly responded to fields at 5.5μV/cm.
The dynamic nature of living animals' electric fields, influenced by the pulsing movements of fish gills, prompted the researchers to explore if Donna and Dolly could sense pulsing fields.
Varying the electric field strength while pulsing it at rates of 1, 5, and 25 times per second, the dolphins demonstrated an ability to detect pulsing fields, albeit with reduced sensitivity compared to steady electric fields. Dolly could only detect the slowest pulsing field at 28.9μV/cm, while Donna detected all three, sensing the slowest at 11.7μV/cm.
The team noted that discovering dolphins' sixth sense of electric sensitivity aids in precise foraging, allowing them to locate hidden fish within the last few centimeters of sediment, a capability not seen in sharks, which sense fish electric fields within a range of 30-70cm.
Additionally, researchers propose that this electric sense may explain toothed whales' orientation to Earth's magnetic field, as dolphins swimming through areas with weak magnetic fields could generate detectable electric fields, potentially allowing navigation based on the Earth's magnetic map.
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