The dusky dolphin is limited to the south of the planet including the tip of the American continent, New Zealand and some southern islands.
Bottlenose dolphins have a broad distribution that includes most of the tropical, subtropical and temperate parts of the ocean where there are several kinds of habitats.
Dolphins are not frequent victims of any predator in the ocean due to their sociability and intelligence, but killer whales and some large sharks are their main natural threat.
Each Killer whale population has a different niche in their habitat and consume different resources, however all are the apex predators of the place they live.
Dolphins evolved from land animals that returned to the ocean due to environment conditions.