| Summary: | Sharks are apex predators that structure marine communities through predation. Despite a large number of studies in other areas, especially the Pacific, there are no quantitative data on the diet of tiger sharks, Galeocerdo cuvier, in the northwest Atlantic Ocean and Gulf of Mexico. Diet was assessed from 169 tiger sharks by life stage, area, and environmental factors. Fifteen prey groups were identified, with teleosts, molluscs, birds, cephalopods, and reptiles being the predominant prey categories. There was an ontogenetic shift in diet, prey size and diversity with an increase in shark size. Molluscs were most common in smaller sharks, while teleosts and reptiles became more important in the diet of larger sharks. Dietary overlap was significant by area (Gulf of Mexico vs Atlantic Ocean) and among all life stages except for young-of-the-year and adult tiger sharks. Overall, tiger sharks in the northwest Atlantic and Gulf of Mexico had diverse diets and exhibited ontogenetic shifts, similar to Pacific tiger sharks. Juvenile tiger sharks also demonstrated selective feeding by targeting gastropod foot over ingesting the entire animal. The results of this study can contribute to developing ecosystem models for tiger sharks in an area where their diet has been studied very little.
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