Cetacea and two (external) limbs that are modified into flippers. Though not as flexible or agile as seals, cetaceans can swim very quickly, with the killer whale able to travel at in short bursts and the fin whale able to cruise at . Dolphins are able to make very tight turns while swimming at high speeds. The hindlimbs of cetaceans are internal, and are thought to be vestigial. Baleen whales have short hairs on their mouth, unlike the toothed whales. Cetaceans have well-developed senses—their eyesight and hearing are adapted for both air and water, and baleen whales have a tactile system
Michael Bigg key discoveries of Dr. Bigg's team was that there were two types of killer whales living near the British Columbia coastline: "residents" which ate almost exclusively fish, and "transients" which hunted marine mammals and other warm-blooded prey. Resident and transient killer whale societies are separate, and the two types tend to avoid each other. The resident killer whale population of British Columbia and Washington is further divided into two "communities", one northern and one southern, that do not interbreed. Another discovery was that resident killer whales have one of the most stable social structures of any animal species. Pods of