A pyramid of sharks, revealed in striking new footage, shows how the animals modify their hunting behaviour based on the type of fish they are gunning for.
The video was captured by a film crew shooting a documentary in French Polynesia, Sharks of the Coral Canyon, for the Khaled bin Sultan Living Oceans Foundation, a US non-government organisation.
The moment captured occurs only once a year, when about 10,000 gropers gather to spawn in a narrow channel, serving up a prime hunting ground for grey reef sharks.
The footage allowed scientists to record which fish the sharks targeted and how often they caught one.
"This research shows sharks modify their hunting strategy based on the type of fish they are targeting - slow and steady for agile fish like fusilier, fast and furious for large fish like groper," said Dr William Robbins of Wildlife Marine and lead author of a study of the sharks, which was published in Coral Reefs, the official journal of the International Society for Reef Studies.
By observing the sharks, scientists found they preyed almost exclusively on the most abundant fish, no matter where the fish sat on the food chain.
This is at odds with traditional theories of shark feeding behaviour, which often suggests sharks just eat large predatory fish.
Captain Philip Renaud, executive director of the foundation, said the research showed "sharks may be able to regulate the balance of reef fish by hunting over-abundant species".
The film reveals how two of the most threatened groups of animals in the ocean, corals and sharks, depend on each other, and must be protected together for their survival, the foundation says.
