Elasmobranchs are renown for their ability to detect the weak bioelectric fields of their prey, even in the absence of other sensory cues. We have measured the bioelectric fields of prey items, quantified the behavioral responses to prey-simulating electric fields, and tested the efficacy of various electrogenic shark deterrents.

Enhanced electroreceptive capabilities may have driven selection for the unique head morphology of hammerhead sharks. The laterally expanded cephalofoil allows hammerheads to possess longer ampullae of Lorenzini tubules which might confer greater sensitivity to weak electric fields. In addition, by spacing the electrosensory pores over a broader area, the hammerhead sharks sample a larger swath of the substratum and thus increase the probability of prey encounter. These hypotheses were tested by comparing the behavioral response of juvenile scalloped hammerhead sharks to similar sized sandbar sharks that possess a typical requiem shark head morphology. Both species were exposed to prey-simulating dipole electric fields and their responses were recorded and quantified using digital video analysis. The sharks oriented to, and bit at the electric field as if it were a natural prey item. The hammerheads did not demonstrate greater sensitivity to the dipole electric fields but would likely demonstrate greater sensitivity if exposed to a large, uniform electric field where the greater ampullary tubule length would provide an advantage. Although they were not more sensitive, the hammerheads did sample a much greater area than the sandbar sharks with equivalent spatial resolution thus providing a greater probability of prey encounter.

Bedore, CN & SM Kajiura. 2013. Bioelectric fields of marine organisms. Physiological and Biochemical Zoology 86(3): 298-311. (with cover)

Wueringer, BE, L Squire Jr, SM Kajiura, IR Tibbetts, NS Hart & SP Collin. 2012. Electric Field Detection in Sawfish and Shovelnose Rays. PLoS ONE 7(7): e41605.

Wueringer, BE, SC Peverell, J Seymour, L Squire Jr, SM Kajiura & SP Collin. 2011. Sensory systems in sawfishs. 1. The ampullae of Lorenini. Brain, Behavior and Evolution 78: 139-149.

Kajiura, SM & TP Fitzgerald. 2009. Response of juvenile scalloped hammerhead sharks to electric stimuli. Zoology 112: 241-250. (with cover)

McGowan, DW & SM Kajiura. 2009. Electroreception in the euryhaline stingray, Dasyatis sabina. Journal of Experimental Biology 212: 1544-1552.

Kajiura, SM. 2003. Electroreception in neonatal bonnethead sharks, Sphyrna tiburo. Marine Biology 143: 603-611.

Kajiura, SM & KN Holland. 2002. Electroreception in juvenile scalloped hammerhead and sandbar sharks. Journal of Experimental Biology 205(23): 3609-3621.

Kajiura, SM. 2001. Head morphology and electrosensory pore distribution of carcharhinid and sphyrnid sharks. Environmental Biology of Fishes 61(2): 125-133.