Opportunistic camera surveys provide insight into discrete foraging behaviours in nurse sharks (Ginglymostoma cirratum)

Elasmobranch fishes (sharks, skates and rays) are some of the most morphologically and behaviourally diverse vertebrates on the planet, demonstrating a wide range of feeding strategies. The nurse shark (Ginglymostoma cirratum) is a large, widely distributed shark species which is commonly associated with tropical and subtropical reefs worldwide; yet it remains vastly understudied relative to other large species. To advance our understanding of nurse shark behaviour and ecology, we used opportunistic video observations gathered throughout the islands of Turks and Caicos from September 2020 to April 2021. We made 233 observations from 78 camera deployments and identified five behaviours, four of which were attributed to foraging. Stationary feeding behaviour was most commonly observed and strongly influenced by habitat type with a greater number of observations occurring on sand banks relative to reef habitat. Unique to this study was the first empirical description of pectoral positioning, by which individuals can position their body relative to a food-source through mobilization of the pectoral fins. We discuss these findings in relation to mechanical processes and kinematics, and the implications of expanding our knowledge of the functional role nurse sharks play in the transfer of energy across tropical seascapes.