Examining shark bite scars on dolphins off Bimini, The Bahamas: Comparisons between bottlenose and Atlantic spotted dolphins

Abstract

AbstractShark predation risk impacts many facets of dolphin life, including habitat use and foraging strategies. Because direct predation is rarely observed, researchers instead examine dolphins in situ for past injuries that can be attributed to sharks. We analyzed existing photo‐ID catalogs of common bottlenose (Tursiops truncatus) and Atlantic spotted dolphins (Stenella frontalis) off Bimini, The Bahamas. A minimum of 29% of individual T. truncatus had evidence of a past, nonlethal shark bite, while for S. frontalis this was only 15%. For both species, shark‐induced injuries were predominantly on the dorsal side. Regression analyses indicated that T. truncatus were more likely to have shark bite scars than S. frontalis and the likelihood of documenting a shark bite scar increased with a higher percentage of the body photographed. T. truncatus were less likely to have scars in the dorsal region, but sampling differences could have influenced these results. While the shark species responsible for scars was not determined, T. truncatus and S. frontalis overlap spatially and temporally with tiger (Galeocerdo cuvier) and bull sharks (Carcharhinus leucas) off Bimini. This study builds on the understanding of dolphin/shark interactions from longitudinal studies of dolphins in this region, providing insight into factors influencing predation risk.