Sharks eat dolphins. Because dolphins form protective circles around the weakest members of their pods and mount attacks against any threats, only the largest sharks attempt to eat dolphins.
Dolphins are close to the top of the food chain. Their main predator in the ocean is the shark, but many sharks and other potential predators avoid dolphins due to dolphins' aggressive defenses. Dolphins are capable of killing sharks. Killer whales have been found with dolphin remains in their stomachs, but as of 2014, it is not known whether they actively attack dolphins or scavenge their remains.
Humans are the primary predators of dolphins. People in Japan, Latin America and other parts of the world consider dolphins a food source. Because dolphins prey on fish that humans catch and eat, fishermen often kill dolphins to keep dolphins from interfering with their catch. Dolphins are also sometimes killed when they unintentionally become entangled in fishing nets.