The largest fish in the ocean today, an adult whale shark can measure up to 40 feet (12.2 m) long and weigh as much as 60 tons. These sharks can be identified by their greenish-gray bodies with the back and sides covered in a distinctive white checkerboard pattern. The head is broad and flat and the mouth can measure up to 5 feet (1.5 m) in width.
This docile animal will slowly cruise through the upper levels of the water column where it feeds mostly on plankton, supplementing its diet with small crustaceans, cephalopods and plants. It is one of only three filter feeder sharks, the others being the basking shark and the megamouth shark. The whale shark eats by opening its mouth and then forcefully expelling water through its gills where filter pads will catch any organism smaller than 3/4 inch (2 cm). Although the whale shark does have teeth, they are considered vestigial.
Although its immense size can be startling, whale sharks pose no threat to people and in recent years diving with them has become a popular form of ecotourism. Despite these frequent interactions with people, the species has not been widely studied.
The whale shark is rarely found outside tropical waters, preferring temperatures of 72 degrees F (22 degrees C) or higher. With the exception of the Mediterranean Sea, it is found in every ocean in the world. The shark is normally found in coastal waters, but it may also enter tropical lagoons.
This shark is currently listed as vulnerable by the International Union for Conservation of Nature (IUCN) due to their declining populations. Dwindling numbers may be the result of over-harvesting, entanglement in marine debris and irresponsible ecotourism which can cause stress or injury to the animals.