Dolphins are sometimes victims to sharks or killer whales. However, their most dangerous threat is the man.
The Orca, Killer Whale (Orcinus orca) is the most widely distributed mammal after the humans. It is an apex predator that weighs up to 6 tons and reach up to 26 feet in length.
Dolphins protect themselves trough a sophisticated social structure which make dolphins swim and live together in small groups called pods or schools
Large species of sharks, eat small species of dolphins or calves. Also, occasionally killer whales eat small dolphins too.
The only predator that the small species of dolphins or calves have in the ocean are the large species of sharks.