These sharks are usually solitary, but loose groups of up to 100 individuals have been sighted, often when they are feeding (5). Whale sharks appear to be highly migratory (2), and have been tracked for thousands of kilometres (7). Individuals who regularly visit the Ningaloo Reef in Australia, between March and May every year, appear to be mainly immature males (8). It is not clear whether movements across deep ocean basins follow prey routes or are undertaken for other reasons. Very little is known about the reproduction of the world's largest fish, but in 1995, one pregnant female was captured who contained nearly 300 foetuses (5). The species is ovoviviparous; the young hatch from eggs retained within the mother so that she then gives birth to live young. Whale sharks are fairly docile creatures and feed on planktonic organisms and small fish by suction filter-feeding (2). This species is thought to be a more dynamic filter-feeder than, for example, the basking shark, actively sucking food in through their vast mouths and passing the water over the gill arches, where prey are retained and then swallowed (5). They have also been observed actively swimming through shoals of fish with their mouth agape or hanging vertically in the water and drawing food into their mouths (8).