The utilization of prey-simulating electrodes to analyze the predatory behavior of the great hammerhead shark (Sphyrna mokarran)

Abstract

A new observation of a great hammerhead shark (Sphyrna mokarran) natural predation on a southern stingray (Hypanus americana) is described in combination with two novel field experiments that investigate both: (1) the sensory cues that elicit S. mokarran foraging responses, as well as (2) the unique prey handling techniques that make this hammerhead such a specialized predator. This study is the first to demonstrate the importance of electro-sensory cues at close ranges for prey detection in S. mokarran. In addition, both the observed natural predation and field experiments provided visual evidence of the repeated prey manipulation technique, termed ‘lateral headshake repositioning’, that may maximize prey handling and foraging success. Further research using more accurate chemo-sensory cues (e.g. those from southern stingrays – Hypanus americana) or varying decoy manipulations (e.g. a buried decoy with active electrodes) is warranted to enhance our understanding of the sensory allocation and prey handling behavioral patterns in relation to the foraging success of this endangered predator.

Keywords:

• Great hammerhead shark
• Sphyrna mokarran
• Cephalofoil
• natural predation
• endangered

Acknowledgements

We thank the Bimini Sands Resort and Marina (G. Johnson and K. Grudecki), Bimini Big Game Club Resort and Marina for permitting us to use their facilities and/or resources to make this project possible. We thank the University of Massachusetts Dartmouth, the WAVE Foundation, Shark Project-Austria, the National Geographic Society Waitt Foundation, Discovery Channel, and the Smithsonian Channel for providing funding to make this project possible. We thank Dr. Stephen Kajiura for his seminal work that helped motivate this study. In addition, this project could not have been possible without the help of a substantial number of volunteers including: N. O’Connell, the DeRosa Family, M. Uchoa, G. Leurs, C. Collatos, R. Jacobsen, R. Reed, S. Reed, Sc. Krauss, St. Krauss, F. Mazucka, L. Mazucka, A. DeMarino, A. Kalista, M. Cugliandro, M. Theo, the Larsen family, L. Smith, G. Brokenshaw. Lastly, we thank the Bahamas Department of Natural Resources for granting us permission to conduct this research.