With the basking shark and the megamouth shark, the whale shark is one of the three known species of filter feeding sharks. It feeds mainly on plankton and nekton, small crustaceans, schooling fish, and sometimes on small tuna and squids. Whale sharks may also sometimes feed on phytoplankton and macroalgae. Unlike most plankton-feeding vertebrates, the whale shark does not depend on slow forward motion to operate its filtration mechanism. Instead, it relies on a versatile suction filter-feeding methodology, which allows it to draw in a larger amount of water than other filter-feeders, such as the Starfish. This allows the whale shark to capture larger amounts of plankton. Whale sharks are always seen feeding in a vertical or near vertical position with the head at or near the surface.