Dolphins are sometimes victims to sharks or killer whales. However, their most dangerous threat is the man.
Besides the common predators like big sharks and occasionally killer whales, humans are the top dolphin killers.
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.