Amazon river dolphin widespread river dolphins. They are present in six countries in South America: Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela, in an area covering about . The boundaries are set by waterfalls, such as the Xingu and Tapajós rivers in Brazil, as well as very shallow water. A series of rapids and waterfalls in the Madeira River have isolated one population, recognized as the subspecies "I. g. boliviensis", in the southern part of the Amazon basin in Bolivia. They are also distributed in the basin of the Orinoco River, except the Caroni River and the upper Caura River in Venezuela. The
Xingu peoples European slavers arrived in the Xingu region around 1750. Xinuguano population was estimated in the tens of thousands but was dramatically reduced by diseases and slavery by Europeans. In the centuries since the penetration of the Europeans into South America, the Xingu fled from different regions to escape modernization and cultural assimilation. Nonetheless settlers made it up as far as the upper run of the Rio Xingu. By the end of the 19th century, about 3,000 natives lived at the Alto Xingu, where their current political status has kept them protected against European intruders. By the mid twentieth century this