Behavioral electrosensitivity increases with size in the sandbar shark, Carcharhinus plumbeus

During elasmobranch ontogeny, increasing body size has been proposed to result in a tradeoff between increased sensitivity and decreased spatial resolution of the electrosensory system, but this hypothesis has not previously been tested. Further, the sensitivity of the electrosensory system has not been examined in any large sharks. In the present study, we examined the behavioral electrosensitivity of large (likely adult) sandbar sharks to prey-simulating electric fields, compared with previously published results for small (juvenile) sandbar sharks. We found that the large sandbar sharks, which were approximately three times larger than the small juveniles previously tested, had lower minimum (0.002 nV/cm) and median (0.5 nV/cm) response thresholds. These represent the lowest sensitivity thresholds of any elasmobranch studied to date. Since electric field detection plays an important role in feeding behavior, increases in sensitivity of the electrosensory system and the corresponding increase in electric field detection distance with growth may be linked to ontogenetic dietary changes.