Dolphins that dance to a different drummer. These are Amazon river dolphins, or botos. (Photo by Stefanie Triltsch)
River dolphins are a different kettle of fish than the ocean-going dolphins we all know and love. There are three types of river dolphins known to be currently still alive, found in Asia and South America, but these unique animals are having a very hard time.
Though they look mostly similar to marine dolphins, river dolphins are distinctive because of their long, narrow beaks, which can be up to two feet long. This is four times the length of an ocean dolphin’s beak. They use this fantastic, toothy mouth to catch fish. In addition, river dolphins have small eyes and poor eyesight compared to ocean dolphins, because they live in sediment-filled muddy rivers where they rely on echolocation instead of eyes.
In South America you will find the Amazon river dolphin, also called the boto, which lives in both the Amazon river basin and the Orinoco River to the north. It is found along much of the entire length of those rivers, and move up and down as water levels change. Its long mouth is useful for reaching into vegetation and tree roots to pull out hiding prey.
The La Plata dolphin also lives in South America, but is found snugged up against the coast in the southeast of that continent. It does not actually live full time in rivers like the others, but is otherwise very similar, and does not venture far from land.
The South Asian river dolphin, found in the Ganges and Indus rivers of India and Pakistan, is endangered due to commercial usage, human development, industrial pollution, and river damming, which fractures their populations and isolates small gene pools.
The baiji, a river dolphin formerly found on the heavily populated Yangtze River in China, was declared extinct in 2006. The last confirmed sighting was in 2004, and a long expedition to find more in 2006 was unable to turn up a single dolphin. If they truly are gone, it is the first recorded extinction of a cetacean directly due to human influence, though of course we have come very close to eliminating several others in the past.
As recently as 1950 there were 6000 baiji on the Yangtze River, but increased industrialization and growing human cities, along with fishing and pollution, reduced their numbers to only a few hundred by 1970. By 1998 only seven were found in a survey. However, a Chinese man in 2007 filmed what may have been a baiji in the river, giving hope that the animal may still live. Yet even if it does, there is essentially zero hope for its future. A special aquarium was once set up to help the species survive, but most of the baiji held there died within a year, and the last passed away in 2002.
With humans using rivers so heavily, for fishing, for transportation, for electricity, and sadly sometimes for waste disposal, the future of the river dolphins remains entirely uncertain.
The Book of Beasts 