Male Bottlenose Dolphins are even known to molest [rape] dolphins of different species.
Male dolphins have been known to engage in infanticide. Dolphins will also kill porpoises for reasons which are not fully understood, as porpoises generally do not share the same fish diet as dolphins and are therefore not competitors for food supplies.
the adorable dolphins you swim with at Sea World may not be as innocent as you think. According to marine experts, the bottlenose dolphin might actually be the only animal on earth that murders fellow underwater inhabitants for the sheer fun of the kill.