(say doll-fins , por-puss-es)
They are not fish.
They are small whales.
They are mammals that live in the sea.
They breathe air like we do.
They have skin, not scales.
Dolphins and porpoises are small whales. They are both in the group of whales known as toothed whales.
What are the differences between dolphins and porpoises?
|Dolphin teeth are cone-shaped, and the top and bottom teeth interlock. They have a melon-shaped head with a beak. They have a dorsal fin.
There are 2 groups of dolphin: short-beaked and long-beaked.
There are 36 species, or kinds, of dolphin, including bottlenose dolphin, Risso's dolphin, false killer whale, Pacific whitesided dolphin, orca (killer whale, the biggest dolphin), longfinned pilot whale, shortfinned pilot whale, and Irrawaddy dolphin.
|Porpoises have blunt heads and small spade- shaped teeth. They grow up to 2m long. They do not have the beak and melon- shaped foreheads that dolphins have.
Porpoise species include the Harbor, Gulf of California, Burmeister's, Spectacled, Finless and Dall's porpoises.
Click here find out about Bottlenose dolphins, the best known species.
Click here to find out about a newly discovered Australian dolphin, the Snubfin dolphin
Most dolphins live in the oceans, but a few kinds live in fresh water. There are four species, or kinds, of dolphins called river-dolphins. As their name suggests, they live only in rivers. They all have a long, slender beaks with many teeth. They have small eyes. Their dorsal fins are less developed than those of ocean dolphins, and their bodies are thicker. They live in muddy river estuaries (where a river meets the sea) and rely on excellent echolocation (sounds that are sent out and bounce back off objects in their path) in order to find their way about.
The existing river-dolphin species are:
•the Indian river-dolphin (sometimes known as the Ganges river-dolphin),
•the Indus river-dolphin, which is almost blind.
•the Amazon river-dolphin (called boto),
•the La Plata dolphin.
All river-dolphins are threatened or endangered.
On 8th August 2007, it was officially confirmed that the
Yangtze river-dolphin (baiji) was extinct after an intense six-week search failed to find even a trace of one in the whole 1,669 km of the Yangtze River. The extinction of this rare animal was suspected in 2006, but is now confirmed.
The team of searchers, which included Chinese government scientists and other conservation experts, used two boats and searched the river four times, listening and looking for the dolphins. The Chinese government had intended the team to find Yangtze river-dolphins and move them to a new, protected, reserve in a lake as part of a program designed to save them. Sadly, this attempt came too late.
The Yangzte river-dolphin numbers had been dropping steadily. They were declared endangered in 1979. In 1998 only 7 were found. The last captive baiji died in 2002.
The Yangtze River is so heavily polluted that it may never recover. It is a major shipping traffic area.
The news release: http://news.mongabay.com/2007/0808-baiji.html
|Official IUCN Classification as Extinct
Extinct means gone forever; a species no longer exists on earth.
The last aquatic mammal to become extinct was the Caribbean monk seal in the 1950s.
Click here to find out more about:
More about Amazon River-dolphins
La Plata River-dolphin
What can we do to help?
There are hints and links here
You can adopt a dolphin to help raise funds to save them. You can find out more here and here.
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If you use any part of this, acknowledge it in your bibliography like this:
Dolphins & Porpoises (2003). [Online], Available: www.kidcyber.com.au
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Whale Strandings...Threats to Marine Mammals
Updated August 2007