Baleen whales do not have teeth, but instead use baleen to filter small prey from sea water. Baleen whales also have two external blowholes while odontocetes have only one. Beyond these physical differences, scientists have uncovered striking differences between the two groups in terms of life history and social organization. This appears to be reflected in their communication. This signature whistle distinguishes an individual, providing a way for dolphins to recognize and bond with others.
Marine mammals are also very adept at imitating sounds.
Hoover, a harbor seal at the New England Aquarium, imitated human speech well enough to have a recognizable New England accent. Logosi, a beluga whale at the Vancouver Aquarium, was able to imitate his own name. And when one dolphin of the Sarasota community, Nicklo, was carried onto a raft to be measured and recorded, it imitated another's signature whistle. Some studies have shown that male dolphins might be better at imitating sounds than female dolphins. The signature whistles and their imitations of two captive bottlenose dolphins named Scotty and Spray at Sealand, a marine park in Brewster, Mass. were compared.