River dolphin. Photos courtesy of David Weller.
The Amazon river dolphin is entirely riverine, inhabiting river channels, tributaries and lakes. It goes by many names and is most commonly referred to as “boto” or “boutu.” It also goes by pink dolphin, bufeo, tonina, and delfin rosado. Boto can be found in 6 countries in South America: Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela. This dolphin inhabits the entire Amazon River and many rivers, lakes, and streams that adjoin it. The boto is listed as endangered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).Amazon River dolphins average 2.1-2.5 m (7-8 ft) in length and have very flexible bodies. They are able to move their head and pectoral flippers in all directions. After birth, calves are dark gray and turn pink as they mature. Adults are pinkish gray on top and light pink underneath. They have a long thin rostrum with short bristles on top. The dorsal fin is not very prominent on the Amazon river dolphin. The dorsal fin is short and keel shaped appearing like a hump instead of a fin. Amazon river dolphins are relatively quiet animals, producing an average of only one vocalization per individual every 10 minutes. When they do vocalize, they do so in bouts of diverse, short duration calls of less than about half a second. Almost all vocalizations are at frequencies below 5 kHz, including whistles that last about 1 second.
River dolphins. Photos courtesy of David Weller.