What we call marine predators includes large pelagic fishes (e.g., sharks and billfish), marine mammals (e.g., seals), seabirds (e.g., penguins), and sea turtles. Despite differences in taxonomic groups, these animals commonly have large bodies, move widely, and play important roles as the top consumers of food chains in marine ecosystems. Their ecology is poorly understood, due to difficulties in studying them in open oceans. Moreover, many marine predators are negatively impacted by ever-increasing human activities and climate changes.

In the past, it was nearly impossible to study the behavior and physiology of marine predators in the wild. However, recent development and improvement of biologging technology(*), or the use of miniaturized animal-borne sensors, made it possible to do so. We use biologging technology as our main research tool. Among many marine predators, we primarily study pelagic sharks both in Japan (Kochi, Okinawa, and our hometown Hayama) and oversea countries (e.g., Taiwan, Australia, and Canada). We also study seals and some seabirds. Our approach is to combine biologging data obtained from wild marine predators with the information on other species in the literature and remotely sensed environmental data. By doing so, we aim at understanding the ecological and evolutionary factors underlying the behavior and physiology of marine predators. We also aim at understanding how marine predators respond to climate changes and other environmental changes associated with human activities.

In biologging, effective use of currently available devices is important, but the development of new devices is even more important. We, therefore, collaborate with several manufacturers and keep trying to record truly novel data from free-swimming marine predators.

↑Biologging in action. From Watanabe and Papastamatiou (2023) Annu. Rev. Anim. Biosci.

(*)Please refer to our review article ”Biologging and biotelemetry: tools for understanding the lives and environments of marine animals" about history, current states, and future perspectives of biologging technology.