Diet of Bottlenose Dolphin, Tursiops truncatus (Montagu, 1821), in the Northwestern Mediterranean Sea

Cetaceans can be considered good natural samplers of biodiversity due to the different hunting strategies they adopt. In this study, the stomach contents of 28 Tursiops truncatus (15 females and 13 males), stranded along Tuscany coasts, NW Mediterranean, between 2008 and 2021, were analyzed. The prey items were identified at the lowest taxonomic level possible, and assessed in terms of abundance, weight, and frequency of occurrence. The index of relative importance (IRI) was also computed. Overall, 2201 bony fishes and 406 cephalopods were identified. The trophic spectrum resulted in high diversity (69 taxa) and the prey species, 53 fishes and 16 cephalopods, live at different levels of the water column. Predation was mainly based on European hake, Merluccius merluccius (%IRI 26.9), and conger eel, Conger conger (%IRI 25.1). The abundant presence of nocturnal species, such as Conger and Ophidion, indicates the nocturnal hunting activity of the bottlenose dolphin. Furthermore, evidence is presented of the dolphins' ability to capture fish at night, taking advantage of the sound produced by these fish to locate them. Diet did not show any statistical differences among sexes, except that females preyed upon a significantly higher quantity of octopods than males.