Passive electroreception in bottlenose dolphins Tursiops truncatus: implication for micro- and large-scale orientation

<p>For the two dolphin species <em>Sotalia guianensis</em> and <em>Tursiops truncatus,</em> it was shown that the vibrissal crypts located on the rostrum represent highly innervated, ampullary electroreceptors and that both species are correspondingly sensitive to weak electric fields. For a comparative assessment of the sensitivity of the bottlenose dolphin's electroreceptive system, we determined detection thresholds for DC and AC electric fields with two bottlenose dolphins. In a psychophysical experiment, the animals were trained to respond to electric field stimuli using the go/no-go paradigm. We show that bottlenose dolphins are able to detect DC electric fields as low as 2.4 &amp;[mu]V cm ^-1 and 5.5 &amp;[mu]V cm ^-1, respectively, a detection threshold in the same order of magnitude as those in the platypus and the Guiana dolphin. Detection thresholds for AC fields (1, 5, and 25 Hz) were generally higher than those for DC fields, and the sensitivity for AC fields decreased with increasing frequency. Although the electroreceptive sensitivity of dolphins is lower than that of elasmobranchs, it is suggested that it allows orientation at micro and large scales. In dolphins pursuing benthic foraging strategies, electroreception may facilitate short-range prey detection and target-oriented snapping of their prey. Furthermore, we discuss that the ability to detect weak electric fields may enable dolphins to detect the Earth's magnetic field through induction-based magnetoreception, thus allowing large-scale orientation.</p>