The hidden life of sharks: Immersion into the behaviour of these predators in a near pristine reef

The extent of the global human footprint limits our understanding of what are natural baselines in the marine environment. Remote near-pristine areas provide some baseline expectations for biomass and suggest that predators can be more abundant than expected. Coral reefs are generally considered from the angle of corals and their associated reef fish communities, but reef sharks have received relatively less attention. I will bring you on a journey to one of the largest aggregations of reef sharks to explore their secret lives. The southern pass of Fakarava atoll – a Biosphere Reserve in French Polynesia – hosts more than 900 reef sharks. This huge biomass of predators makes the trophic pyramid locally inverted. Based on advantageous characteristics of the channel, sharks rely on home food delivery to overcome their hunger. Recurrent fish spawning aggregations and other subsidies represent external energy which frequently feeds this locally inverted trophic pyramid. These generalist predators feed on more than 40 prey species and developed collective hunting strategies to improve foraging efficiency leaving little chance for prey to escape. Using cutting-edge technologies, this research opens a new window on the natural shark behaviour, feeding ecology and social behaviour in a unique healthy reef to better understand the role of sharks on the local ecosystem and how such concentrations of predators are maintained.