Dolphins and whales are large marine mammals of the order Cetacea. They are believed to be descendants of terrestrial mammals, most likely of the Artiodactyl order. The term whale generally refers to all cetaceans except dolphins and porpoises.
Dolphins and whales have forelimbs modified as fins and nasal openings (blowholes) on top of the head. The end of the tail is composed of two flukes, and is used for propulsion. Other similarities include their sense organs, vocalization and sleeping methods. Dolphin and whales hunt for food by use of echolocation. i.e. they direct clicks into the water and listen to the strength of the rebounded echo from which they know the distance from the feed.
- Baleen whales have two blowholes. No known species of dolphins have two blowholes.
- Whales have body hair. Dolphins do not have body hair the only exception is the Boto river dolphin
- Baleen whales have a row of plates on the upper side of their jaws that resemble the "teeth" of a comb. Some species have teeth like the sperm whale. All species of dolphin have teeth, some have up to 250 teeth.
edit Video: Killer whales hunting a dolphin
This video shows a group of five orcas hunting a dolphin that is exhausted and separated from its pod. It was shot off the coast of South Africa. Despite their name, orcas (killer whales) actually belong to the dolphin family.
Dolphins and whales are equally intelligent. After years of research, scientists have said that cetaceans (including porpoises, dolphins and whales) are highly intelligent, and should therefore have rights just like humans.
edit Social Behavior
Whales are known to teach, learn, cooperate, scheme, and even grieve. Some species communicate with melodic sounds, known as whale song others make click like sound which can be very loud. Whale vocalizations seem to serve many purposes, like echolocation, mating, and identification. Scientists studying whale and dolphin communication repertoires have estimated that
bottlenose dolphins have a repertoire of 27 single letter syllables, five 2-letter syllables and four or five 3-letter syllables. By contrast, humpback whales have a repertoire of only six single letter syllables but use seventeen or eighteen 2-letter syllables (the data is not extensive enough to reveal the repertoire of 3-letter syllables).
Dolphins are social, living in pods of up to a dozen individuals. In places with a high abundance of food, pods can merge temporarily, forming a superpod, which may exceed 1,000 dolphins. They communicate using a variety of clicks, whistles and other vocalizations, and ultrasonic sounds for echolocation. Dolphins can establish strong social bonds. They will stay with injured or ill individuals, even helping them to breathe by bringing them to the surface if needed.
Here's a video showing a group of dolphins helping an injured group member stay on the surface (read accompanying story):
edit Calling each other by name
A study has shown that bottlenose dolphins name themselves using a unique whistling sound and, when separated or otherwise stressed, call their loves ones (such as a mother or a close male friend) by their "name". Other than humans, dolphins are the only known species know to be able to do this.
Baleen whales such as humpbacks and blues feed only in arctic waters, eating mostly krill. The humpback whales form a ring of bubbles around their prey and thus obstruct their path of escape. Watch this video: Humpback Whale: Hunting Technique
Certain species of dolphins come closer to shore for feeding. They also chase fish into shallow water to catch them easily. Another method which they adopt is driving prey onto mud banks for easy access. Watch this video: Atlantic Bottle Nose Dolphins mud-ring feeding
edit "Whales" that are genetically dolphins
Six species in the family Delphinidae are called "whales" but genetically are dolphins:
- Melon-headed Whale, Peponocephala electra
- Killer Whale (Orca), Orcinus orca
- Pygmy Killer Whale, Feresa attenuata
- False Killer Whale, Pseudorca crassidens
- Long-finned Pilot Whale, Globicephala melas
- Short-finned Pilot Whale, Globicephala macrorhynchus