­­Forensic determination of shark species as predators and scavengers of sea turtles in Florida and Alabama

Abstract Sharks are the primary predator of large immature and mature sea turtles, yet the shark species responsible for both lethal and non-lethal injuries are rarely identified because attacks are infrequently observed. Forensic analysis of bite wounds can be used to accurately assess size and potential shark species, especially when combined with species-specific feeding behavior, geographic distribution, and habitat preference. The objective of this study was to use forensic analysis of bite damage on sea turtles to infer shark size and species. Photographs from thirteen cases of documented shark scavenging (N = 3) and predation (N = 10) attempts on sea turtles were retrospectively analyzed, including nesting, free-ranging, and/or dead stranded loggerhead (Caretta caretta), green (Chelonia mydas), Kemp’s ridley (Lepidochelys kempii), and leatherback (Dermochelys coriacea) sea turtles in Florida and Alabama, USA from 2010–2020. Mean interdental distance (IDD) and bite circumference (BC) of wound marks on sea turtles strongly suggest that the bite marks were generated by white sharks (Carcharodon carcharias) in three cases, tiger sharks (Galeocerdo cuvier) in three cases, and bull shark(s) (Carcharhinus leucas) in one case. For three cases with less distinct wound patterns, two likely shark species were identified, and thereafter narrowed down to a single species based on bite mark characteristics. Due to indistinct IDD and BC ranges of bite wound patterns, a single shark species was not identified in three cases. Forensic analysis enables more accurate evaluations of which shark species predate and scavenge sea turtles, and is a useful technique for studying the behavioral interactions of sharks and turtles more closely.