Hobbies And Interests
Feeding Niches
Sharks in the Indian Ocean pursue a broad range of predatory strategies. The biggest of all fish, the whale shark, is mainly a huge filter-feeder, passively straining out zooplankton in a manner similar to the great baleen whales for which it is named (though whale sharks will occasionally consume other prey like small fish). By comparison, the great white shark, which may exceed 20 feet in length and 2 tons in mass, hunts large prey like tuna, seals, sea lions, dolphins and small whales. The much-smaller cookiecutter shark, usually under 2 feet long, targets surprisingly similar species: it has large teeth and a suction-like mouth, which it employs to corkscrew off strips of flesh from large seagoing creatures.
Coastal Species
The reefs and seagrass beds of the coastal Indian Ocean support a rich array of sharks adapted to these fertile, relatively shallow-water habitats. One species that is essentially restricted to coastal areas is the zebra shark, a striking-looking fish with a humped, ridged body, an enormous tail and a blunt head. Patterned when young like its namesake, with a dark body and white stripes, zebra sharks grow lighter in color as adults and boast small, dark spots. They roam coral reefs and sandy benches, snatching crustaceans, mollusks, fish and other small prey from the sediments and crevices. Tiger sharks also regularly cruise coastal waters, hunting nearly anything they can catch, from fish and lobster to sea turtles and dolphins. Growing to 18 or 20 feet long, they are among the biggest of the Indian Ocean's shark species, and one of its apex predators.
Open Ocean
White sharks were once thought to be coastal predators, essentially tied to colonies of seals and sea lions. Contemporary research in the Indian Ocean and other locations suggests otherwise. One female white shark, tagged by researchers in 2003, covered more than 12,000 miles in a round-trip journey across the Indian Ocean between South Africa and Australia. Other open-ocean specialists, like the oceanic whitetip shark, roam constantly through the pelagic environment, as food sources are scattered widely and erratically.
Freshwater Explorations
One notable Indian Ocean shark is not restricted to ocean waters. Along with the tiger and white shark, the bull shark is perhaps the most notorious species in the basin, often implicated in attacks on humans. This burly, powerful requiem shark, which may grow 13 feet in length, is also known for its tolerance of freshwater: it may swim hundreds or thousands of miles upriver, traveling freely between marine and riverine environments. Along the Indian Ocean margin, they regularly utilize habitat in the Zambezi River system of southern Africa, where they share space with such inland creatures as hippos and Nile crocodiles.