Within each pod, some dolphins are more dominant than others. Natural predators pursue dolphins. Sharks are a dolphin's main predator. Dolphin remains are often found in the stomachs of tiger sharks, dusky sharks and bull sharks. On occasion, killer whales may feed on some species of dolphins.
Human activities can harm dolphins.
In some parts of the world, humans hunt certain types of dolphins for food. Yet even where they're not hunted, dolphins are threatened by some human activities. Toxic chemicals that pollute nearshore waters may contaminate the fish on which dolphins feed. Scientists believe these chemicals might affect the health of dolphins and cause tumors. Pollution may have contributed to the deaths of dolphins that have washed up on beaches in recent years.