Bottlenose dolphins are known for their intelligence, social skills, and echolocation abilities. But did you know that they also have a sixth sense that allows them to detect weak electric fields in the water?
The Discovery of Electroreception in Bottlenose Dolphins
MORTEN STRICKER/Ritzau Scanpix/AFP via Getty Images
A recent study by researchers from Germany and the United States has revealed that bottlenose dolphins (Tursiops truncatus) can sense electric fields using structures on their snouts called vibrissal crypts.
These are the remnants of whiskers that dolphins have as newborns but lose soon after birth.
The researchers found that the vibrissal crypts undergo a transformation from mechanoreceptors to electroreceptors, similar to what happens in the Guiana dolphin (Sotalia guianensis), the only other cetacean species known to have electroreception.
The researchers conducted a behavioral experiment with four bottlenose dolphins at the Nuremberg Zoo in Germany.
They trained the dolphins to respond to acoustic stimuli in a go/no-go paradigm and then tested them for stimulus generalization with different types of stimuli, including electric fields.
They found that all four dolphins responded spontaneously to the first presentation of an electric field, and three of them showed perfect transfer by responding consistently to electric field amplitudes as low as 0.5 mV cm-11.
The study also involved an anatomical analysis of the vibrissal crypts of neonate and adult bottlenose dolphins.
The researchers discovered that the neonates still possess almost complete vibrissal follicles, including a hair shaft, hair papilla, and cavernous sinus, but these features are lost in adults.
Thus, the vibrissal crypts show a similar postnatal morphological transformation from a mechanoreceptor to an electroreceptor as in Sotalia.
However, the innervation density of the vibrissal crypts was high and almost equal in both, neonate and adult animals, indicating that they are functional throughout the dolphin’s life.
The Implications of Electroreception in Bottlenose Dolphins
Electroreception is a rare sensory modality in mammals, and is mostly found in aquatic or semi-aquatic animals, such as platypuses, echidnas, and some rodents.
It is thought to facilitate prey detection and localization, especially in murky or dark environments.
For dolphins, electroreception could be useful for finding benthic prey, such as fish and crustaceans, that hide in the sand or mud.
This is supported by the observation that some bottlenose dolphins use a foraging strategy called crater-feeding, where they create depressions in the seafloor with their snouts to expose hidden prey.
The discovery of electroreception in bottlenose dolphins also suggests that this ability might be more widespread in cetaceans than previously thought.
The researchers speculate that electroreception could have evolved independently in different dolphin lineages, or that it could be a primitive trait that was retained or lost in different species.
This electroreception could be related to the evolution of echolocation, as both sensory systems rely on the detection of physical signals in the water.
Electroreception is a fascinating example of how dolphins have adapted to their aquatic environment and how they use their remarkable senses to explore and interact with their surroundings.
The next time you see a bottlenose dolphin, you might wonder what kind of electric signals it is picking up with its snout.
