There are two species of dolphin that can be found in the Southern Ocean. The Hourglass dolphin is the only species found throughout the Antarctic waters. It is less than 7 feet long, and is black and white in color. They are the most southerly of all dolphins. The southern rightwhale dolphin sometimes enters southern waters, but it is basically a warm-water species.
Baleen whales are much larger than toothed whales.
Baleen whales eat mostly plankton. In order to get enough to eat, they continually gulp water and plankton into their mouths or just swim with their mouths open. The baleen acts as a filter so that the whale can expel the water and swallow the plankton and small fish. Southern right whales were very popular to hunt in the 19th century. That's how they got their name . . .