Looking for big pink: South America's river dolphins are disappearing, but Vera da Silva is out to change that - Brazilian biologist

International Wildlife, Nov-Dec, 1997 by Virginia Morell

Botos are built for flexibility. Like their extinct ancestors, they have unfused neck vertebrae, enabling them to turn their necks. (Nearly all other dolphin species, including the tucuxi, have fused vertebrae, making them rigid.) Not only can botos turn their necks, they can scull forward with one flipper and paddle backwards with the other. This maneuverability gives them an advantage over the tucuxis in the Amazon's flooded forests--vast tracts that are underwater for at least six months a year.

One such flooded forest is found in the Mamiraua Reserve. Here tree trunks--and the earth--emerge only when the dry season sets in, as it has now, in September. Instead of an almost continuous lake of water, there are narrow river channels and lagoons separated by stretches of land and dense forest. For the dolphins, this watery world is an idyllic home, partly because they are protected from fishermen's nets here (local villagers have agreed to stop fishing and hunting in exchange for work in the reserve) and partly because of an abundance of fish.

Botos are not particular about the kind of fish they eat; da Silva found that they prey on nearly 50 species from 19 families. Their favorite is the catfish, which they're thought to catch sometimes by reaching into the fish's mudbank den with their long, pink beaks. They capture most of their prey, however, via echolocation, emitting a series of clicks and cracking sounds as they chase a fish. These act much like a bat's sonar system, telling the dolphin exactly where the fish is.

"They're excellent at fishing," says da Silva, "which is why I first began to study them. Fishermen were complaining that the botos only hunted the best fish--the most commercial ones. But I showed that's not the case; they eat almost any kind." In the early 1960s, the Brazilian government suggested culling botos to help preserve the Amazon's fisheries industry, a plan that was not carried out. Da Silva's research showed that such drastic measures were unnecessary, but fishermen still are not fond of the creatures.

Yet the dolphins are seldom hunted, apparently because local people fear them, too. "They have many myths and stories about the botos," says da Silva. "It's thought they can take the shape of handsome young men. Then they come ashore and seduce people's wives and daughters." Sometimes women give birth to infants with spina bifida, a birth defect that prevents the baby's skull from growing properly, leaving an opening in the head that can resemble a boto's blowhole. "So they say those are the botos' babies," says da Silva. Others think the dolphins are evil, since the creatures sometimes swim beneath their canoes, or grab their paddles--as if the botos wanted to tip them over. Da Silva, however, thinks the botos are only playing.

But the botos do cause real damage. They're notorious for tearing holes in fishermen's nets, then stealing all the fish. "One fisherman recently told me how he badly beat and burned a boto because he thought it was taking fish from his net," says da Silva. The man's next child looked exactly like a baby dolphin and died soon after birth, he told da Silva. "That so frightened him, he said he would never kill another boto."