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All over the planet, our oceans are teeming with fascinating marine life – much of which we still know little about. And, while they cover around 70% of Earth, we've only explored 5% of our oceans. Through his magnificent Blue Planet II documentary series, eminent naturalist Sir David Attenborough has taken his own explorations to the limit and captured some of the most fascinating animal behaviour ever seen. The Incredible Bird Eating Fish In Series 1, One Ocean, the Blue Planet II team filmed the compelling hunting behaviour of the Giant Trevally, which has the brain capability to calculate the altitude, airspeed and trajectory of a bird from beneath the surface of the ocean. While they are usually solitary hunters, a school of around 50 trevallies had come from neighbouring reefs, attracted by an abundance of vulnerable fledgling terns. The astonishing footage captures these streamlined silver fish leaping out of the water, mouths wide open, with the perfect precision to ensnare the hapless terns on the wing and devour them in one gulp. The Giant Trevally Caranx ignobilis is found in abundance throughout the tropical and sub-tropical oceans of the world. They thrive in shallow coastal waters around reefs and lagoons, and even adults who venture further out into deeper waters return to the shallows to hunt and reproduce. Once they reach maturity they tend to become solitary, only coming together to breed and, rarely, to hunt. This makes the Blue Planet footage of great value in terms of research. The species has a recorded maximum length of 170cm (weighing in at about 80kg), but fish of this size are rare and they more commonly reach maturity at around 80cm. Ranging in tones of silvery grey, as they mature they begin to show some sexual dimorphism, with the males often colouring to a deep black and females remaining lighter. They have a two-part dorsal fin, and anal, pelvic, pectoral and causal fins – all of which contribute to their speed and agility in the ocean. A Predator at Work As a predatory hunter, the Giant Trevally favours different feeding times depending on the location of its habitat. Its diet consists of smaller fish, crustaceans and cephalopods, again, varying from region to region. They've also been known to follow in the wake of sharks, waiting for discarded prey, and to dine on dolphins, juvenile turtles and, as shown in the Blue Planet II footage, fledgling birds. The trevally's eye takes in a panoramic view of its surroundings, due to a horizontal stripe that affords them a wider field of vision. They're able to detect prey (and predators) without having to move the eye. Studies have shown that when they do come together to hunt in groups, their strategy of breaking up a school of prey allows them to be more efficient. One takes the lead while the others follow behind, individually striking and stunning the prey as they disperse the school. Despite the increased efficiency, however, the species does not rely on this kind of co-operative hunting for its survival. Groundbreaking Footage The Seychelles, where Sir David Attenborough captured his extraordinary footage, is the only place in the world where the species has been observed breaking the water to feed on birds. Even as they travelled to the region, the Blue Planet II team had no idea whether the bird eating fish was myth or truth, but the gamble paid off and, after a week of shooting, produced the absolutely outstanding sequence – all the more dramatic when shown in slow motion. Explore the Last Frontier on a Wildlife Cruise While not everyone has the access of Sir David Attenborough to our natural world, a dedicated wildlife cruise around any of our oceans or natural waterways is a wonderful way to explore what are truly the last great wilderness areas on the planet. With itineraries that take in both exotic and more familiar regions, a well-organised wildlife cruise affords nature lovers the opportunity to encounter our planet's fascinating marine and terrestrial species up close and (almost) personal. Author Plate Marissa Ellis-Snow is a freelance nature writer with a special interest in marine species. For nature lovers interested in dedicated wildlife cruiseitineraries, Marissa recommends the tours organised by Naturetrek, which have brought her unforgettable sightings of a wide range of species in one of the most spectacular regions on Earth.
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