Hobbies And Interests
Appearance
Freshwater river dolphins vary in size slightly, with Amazon River dolphins being the largest. They grow to be between 8.25 and 9.75 feet and weigh and average of 200 lbs. Smaller species, like the Indus River Dolphin, are 5 to 8 feet long and weigh less than 200 lbs. Most have the same or similar physical features, though. Their bodies are heavy and thickset with bulbous domed foreheads and long, slender beaks. These beaks hold between 24 and 34 molar-type teeth that are used to grasp prey. Some freshwater dolphins are gray, but some, like the Amazon River Dolphin, turn pink and then white with age.
Geography
Freshwater dolphin species exist in various parts of the world and are defined, in part, by the waterways they call their home. Two species, grey and pink variations, are found in the Amazon basin and extending waterways in Peru and Brazil. The Indus River dolphin is endemic to Pakistan, but can be found in some waters in surrounding nations. There was also a species of freshwater dolphin in China called the Yangtze River dolphin. As of 2007, it is believed to be extinct, or functionally extinct, after a six-week search effort failed to spot a single member of the species.
Social Behavior
All dolphins are social animals. However, freshwater dolphins do not have any natural predators, except for humans, so they do spend some time on their own. The pink Amazon River dolphin, for instance, hunts alone but may spend some of its time in small family units of five to eight dolphins. Gray river dolphins are a bit more social and seem to have stronger ties to their own kind.
Diet and Hunting
The diet of freshwater dolphins is similar to that of saltwater dolphins. They eat small freshwater fish, catfish and crustaceans. When hunting in floodplain forests, shallow water or narrow passageways, they rely on an unusual feature: unfused vertebrae in the neck. This allows the dolphins to turn their heads 180 degrees to better hunt and catch their prey. Freshwater dolphins are also nearly blind. Their eyes are able to pick up the direction and intensity of light, so they are still used as direction-finding tools, but that's it. Otherwise, freshwater dolphins do not see what they hunt well, and rely on touch and changes of light to catch prey.