Electroreception in neonatal bonnethead sharks,<Emphasis Type="Italic"> Sphyrna tiburo</Emphasis>

The ability of sharks to orient to weak electric fields is well documented, but a detailed analysis of orientation pathways is lacking. Digital video analysis was used to quantify the behavioral response of naïve neonatal bonnethead sharks, Sphyrna tiburo, to prey-simulating weak electric fields. Sharks less than 24 h post-parturition failed to demonstrate a positive feeding response to the electrodes whereas vigorous biting at the electrodes was observed in all sharks greater than 32 h post-parturition. Orientation behaviors were classified as one of five types: "straight" approach, "single turn," "overshoot," "spiral tracking," and "orient without biting." One-third of all orientations were elicited at stimulus intensities of less than 20 nV cm^?1. The median electric stimulus threshold for initiation of orientation was 47 nV cm^?1 and the minimum was less than 1 nV cm^?1. Most orientations to the dipole were from a distance of less than 10 cm with a maximum orientation distance of 22 cm. The innate feeding response to electric stimuli is demonstrated for the first time in a chondrichthyan fish.