The boto is the largest of the 5-ish river dolphins (number six, the tucuxi, lives in both fresh and saltwater with a subspecies living in the Amazon river). Like ocean-swelling dolphins, the boto uses echolocation to hunt; but there are several unique features that set this dolphin apart.
First is the shape of the body and the fins – the boto’s body is thick and sturdy, with a short dorsal fin that forms a triangular ‘hump’ on the dolphin’s back rather than a typical fin; the front flippers and the tail are broad and paddle-like, which increases maneuverability.
Second is the boto’s neck – other dolphins have fused vertebrae (neck bones) that reduce how much they can move their necks. If you have ever injured your neck and wore a neck brace you can probably imagine that stiff and limited movement. Vertebrae in the boto’s neck are not fused, they allow 90o range of motion up, down, and side-to-side. Imagine stretching out your neck after getting the brace removed… freedom! This flexibility makes the boto’s hunting technique possible: it sweeps it’s head back and forth, scanning the river using echolocation.
Third, and probably most striking, is the boto’s color – pink! This dolphin may be many shades of pink throughout its life. Young botos are a dark grey with a lighter belly. As they age, pink coloration starts on the belly and travels upwards towards the back. Older dolphins can be varying shades of pink from a light almost white hue to bright and vibrant pink. Scientists don’t really know what causes the pink color, but one hypothesis is that the boto’s veins and blood vessels are very close to the surface of the skin which creates a ‘rosy glow’.
Fun Fact: Botos actually get pinker when they are excited or surprised. This may be similar to blushing in humans.
Boto live in the Amazon river, pretty much anywhere they can reach without venturing into salt water. They feed along the bottom of the river; eating fish, crabs, and sometimes turtles. Unlike oceanic dolphins, botos are primarily solitary animals. They may occasionally work together to herd fish, but they are usually alone or in pairs (mother and child).
Despite being solitary animals, they are not shy and will often approach boats to satisfy their curious nature. Amazonian locals have told stories of being rescued and pushed to shore by these dolphins. In some areas of the Amazon, botos are considered sacred and individuals believe that it is extremely bad luck to kill them and even worse to eat them. Most likely, this belief has played an important role in preserving the boto’s populations. Even so, botos are classified as an endangered species.
Threats to the boto include entanglement (being caught in fishing nets), injury from being chased away from a fishermen’s catch, injury by boat propellers, habitat loss due to changing river patterns from dams and irrigation, pollution from agricultural pesticides and gold mining (mercury use), and competition with fishermen for food.