The group of cetaceans known broadly as dolphins comprises many distinct types. The four species of river dolphin have caused taxonomists difficulties in recent years and have been classified in different ways. Current thinking is that they comprise four distinct families with a single genus in each. Although river dolphins share some cranial characteristics with long narrow jaws they are in fact quite distinct from one another. Some lesser known facts about dolphins indicate that only three of the four families live in rivers, they are the Ganges and Indus River Dolphins, the Amazon River Dolphin and the Yangtze River Dolphin. The Franciscana lives in coastal and estuarine marine waters off the Eastern coast of South America. There are only two living species of Monodontids, the Beluga and the Narwhal. Taxonomists have disagreed as to where they belong in classification terms and several have regarded them as members of the Delphinidae even though they have distinct morphological differences, which include tail flukes that are convex on the rear margin, broad, short flippers and a lack of a dorsal fin. These facts about dolphins make it difficult for taxonomists to decide exactly which families these animals belong in.
The social organization of the animals that comprise the order Cetacea vary widely from one another, ranging from the solitary behaviour of many of the baleen whales to the apparently more structured society of many of the toothed whales, particularly the dolphins. We use different terms to describe the groups of dolphins that we see. A group may well be an aggregation of animals that have come together around a common resource of food or breeding grounds but may well fragment into smaller more discrete units when the stimulus for coming together is removed. The use of the term pod or school when describing dolphins may imply a degree of cooperation and communication between the individuals making up the pod. Alternatively, a single dolphin such as the Dingle Bottlenose Dolphin, although alone when associating with humans, may well be in touch acoustically with others of his kind over a distance of some miles. These and other dolphin facts show that some gatherings of the larger dolphins stay together for the entire lives of the individuals within the group suggesting that there is a great deal of cooperation that depends on long term bonding between individuals. The dolphins and other toothed whales tend to have more complex social organizations than the baleen whales and in some species, such as Sperm Whales, the males may leave the group when they reach sexual maturity. These dolphin facts suggest that the behaviour, communication and social organization of a wide range of dolphins and other cetaceans is complex yet poorly understood.
Facts About Dolphins in Ireland
© Whale Watch West Cork Ireland 2005-2009
Use of this site constitutes your acceptance