Marine mammals -- Dolphins

Dolphins are marine animals which live in water. They are vertebrate animals and are almost forty species of dolphin in seventeen genera. They vary in size from 1.2m and 40kg, up to 9.5m and 10 tones. They are mostly found at shallower seas of the continental shelves. Besides that, they are carnivores and mostly eating fish and squid. Dolphins are among the most intelligent animals and have made them popular in human culture. The dolphins are social living in pods of up to a dozen individuals. Individuals communicate using a variety of clicks, whistles and other vocalizations. Dolphins are also been known to kill porpoises for reasons which are not fully understood, as porpoises generally do not share the same food with dolphins and are therefore not competitors of food supplies. Dolphins occasionally leap above the water surface. Generally, dolphins sleep with only one brain hemisphere in slow-wave sleep at a time. Besides of humans, dolphins also have a few natural enemies such as larger species of sharks or dolphins.
        Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen genera. They vary in size from 1.2 m (4 ft) and 40 kg (90 lb) (Maui's Dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 LT; 11 ST) (the Orca or Killer Whale). They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating fish and squid. The family Delphinidae is the largest in the Cetacean order, and relatively recent: dolphins evolved about ten million years ago, during the Miocene.

        Dolphins are among the most intelligent animals and their often friendly appearance and seemingly playful attitude have made them popular in human culture.
There are 32 different species of oceanic dolphins, 5 species of river dolphins, and 6 species of porpoises. The lifespan of bottlenose dolphins varies greatly between regions and populations. The average range is approximately 35-55 years, depending on the population..

        The name dolphin is originally from Ancient Greek δελφίς (delphís; "dolphin"), which was related to the Greek δελφύς (delphys; "womb"). The animal's name can therefore be interpreted as meaning "a 'fish' with a womb". The name was transmitted via the Latin delphinus, Middle Latin dolfinus and the Old French daulphin, which reintroduced the ph into the word.

        The word is used in a few different ways. It can mean:
• Any member of the family Delphinidae (oceanic dolphins),
• Any member of the families Delphinidae and Platanistoidea (oceanic and river dolphins),
• Any member of the suborder Odontoceti (toothed whales; these include the above families and some others),
• Used casually as a synonym for Bottlenose Dolphin, the most common and familiar species of dolphin.

        Porpoises are belong to suborder Odontoceti, family Phocoenidae. Orcas and some closely related species belong to the Delphinidae family and therefore qualify as dolphins, even though they are called whales in common language. A group of dolphins is called a "school" or a "pod". Male dolphins are called "bulls", females "cows" and young dolphins are called "calves".

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