The bottlenose dolphin's diet consists primarily of fish and marine invertebrates. Other dolphins eat a variety of foods depending on their species, available food and the methods they have learned for hunting.
Most dolphins vary their diet based on what is available. During one season, they may eat salmon, but when salmon move to freshwater streams to spawn, the dolphin's diet changes to herring and mackerel. Bottlenose dolphins require 4 to 6 percent of their body weight daily in food; however, the weight of food required depends on the fat content. It takes more low-fat squid to provide the energy for a dolphin's activities than high-fat herring or mackerel.
While individual dolphins sometimes eat an individual fish, groups of dolphins often work together to herd schools of fish closer together. The dolphins then take turns diving through the concentrated school of fish to eat. While dolphins have teeth, they do not chew their food. They break pieces off larger fish by hitting them on the bottom of the ocean floor.
Orcas are a larger species of dolphin and have a wider variety in their diet. Some Orcas eat only fish, but others include marine mammals and birds into their diet. Like other dolphins, their exact diet depends on where they live and what is available.