The manta ray's diet consists mainly of the small plants and animals that make up plankton. They also eat shrimp, crab and small fish that are swept up in the process of filter feeding.
Manta rays hunt using both sight and smell. Once prey is located, the manta rays herd their food by swimming around a group of plankton in tightening circles until there is a concentrated mass of the organisms. Then the manta ray tightens its cephalic fins around its mouth to form a funnel and swims, open-mouthed, in a straight line through the mass. Spongy plates along the animal's gills collect the food, and the filtered water passes through the gills back into the ocean. The food is then pushed into the manta ray's stomach.
The largest manta rays grow in excess of 20 feet wide, weigh over 2,900 pounds, and consume up to 60 pounds of food per day. They primarily hunt at night, but hunt both day and night if food is scarce. Manta rays are attracted to coral reefs and areas where sea animals gather to have parasites removed by cleaner fish and shrimp. The manta rays remember these areas and return frequently to hunt.