Common names for the pink dolphin (Inia geoffrensis) include the Amazon River dolphin and the boto. This freshwater cetacean lives in South America's Amazon and Orinoco rivers and their tributaries. During the rainy season, the species also ventures into lakes and flooded rainforests. The largest river dolphin, a boto grows up to 8 feet long and weighs as much as 400 pounds. Unlike any other river dolphin, the male of the species grows significantly larger than the female.
The boto's distinctive bulbous forehead slopes steeply forward and can change shape because of the presence of the animal's melon. The dolphin uses muscular control to alter the shape of its melon for echolocation purposes, to receive and understand input coming back from sounds the animal makes with its mouth. Like other cetaceans, the pink dolphin uses echolocation to make sense of its environment, enabling it to navigate and locate prey. Marine biologists have identified at least 10 distinct calls the boto uses for echolocation.
Teeth and Beak
Unlike any other cetacean, pink dolphins have two different shapes of teeth in their distinctively long beaks. They use the conical teeth in the front of their mouths to catch and hold prey. Their molar-like rear teeth are flanged and used for crushing food before swallowing, enabling them to safely eat crustaceans and other marine animals with shells. Stiff hairs line the top and bottom of botos' beaks, an important adaptation that gives the dolphins greater sensory information as they forage for food in the mood and traverse shallower water.
Unlike many other dolphins, none of the vertebrae in a pink dolphin's neck are fused, which means it can move its head in all directions independent of the rest of its body. This particular feature means the animal can more easily navigate the shallow water and move around trees in flooded forests. Despite its size and robust body, a boto can swim through narrow pathways with flexibility and ease.
Fins and Fluke
Pink dolphins have a ridge on their backs that rises to a low hump where a dorsal fin would be on most other dolphins, making it easier for them to swim in shallow water. They also have proportionately larger fins and broad, triangular flukes. The size of their fins and flukes enable them to maneuver more easily in even the shallowest tributaries. Their pectoral flippers have longer bones than in other dolphins, which enables them to move their fins in a completely circular motion. While all of these physical adaptations increase pink dolphins' ability to maneuver in the rivers and tributaries where they live, they also make them much slower swimmers than marine dolphins.
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