River Dolphin
Some of the most unusual and least known dolphins are found not at sea but in some of the muddy rivers of Asia and South America. There are also some of the most endangered of all cetaceans. There are thought to be fewer than 500 surviving Indus River Dolphins, and only barely more than 150 Baiji, which live in the Yangtze River in China.
All river dolphins share many features which mark them as unusual among the dolphin family. They have an unusually long beak with many small teeth. They have a large, bulging forehead, and extremely large flippers. Overall, river dolphins are very small. Even the largest, the Boto, is only slightly longer than an adult human is tall. River Dolphins also have very tiny eyes, and are nearly blind - in the muddy waters they inhabit, it wouldn’t do them much good to see, anyway.
Compared to oceanic dolphins, river dolphins seem sluggish and slow. They seldom swim very quickly, and rarely if eve show themselves above the water apart from lifting their beaks in the air. They have, however, the most advanced echolocation abilities of any cetaceans - this allows them to see their way around in their muddy environment, and makes up for their poor eyesight.
Did you know that although they are small, some river dolphins have powerful blows when they surface? the Boto, a 6-8 foot (1.8-2.5 meter) long river dolphin in South America, blows spray as much as 6.5 feet (2 meters) into the air. This is nearly twice as high as the blow of the Pilot Whale, a cetacean nearly three times as long and twenty times heavier than the Boto.