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

Even if such myths help protect the dolphins from attack or hunting, the animals still die from human activities, such as being trapped in fishing nets and drowning. But the biggest threat to both botos and tucuxis is from pollution and dams. "These are the things that destroyed the river dolphins in other countries," says da Silva, who launched her in-depth study of the Mamiraua's botos when the Brazilian government proposed building 81 hydroelectric dams in the basin. "They were going to do this, and yet nothing was known about the botos' movements," says da Silva, shaking her head. (The plan is temporarily on hold.)

It was to answer this question that da Silva began closely tracking the Mamiraua botos. Because the dolphins rarely show much more than their dorsal fins, making identification difficult, da Silva has marked 56 of the animals with brands; another 12 have distinctive natural dorsal markings. She and her colleague, Tony Martin from Cambridge University's Sea Mammal Research Unit, have also radio-tagged a dozen botos and built three tracking towers in the reserve.

The research project requires da Silva to leave her home and her two adolescent daughters in Manaus for two weeks every month. "I'm always torn," she concedes. "If I'm home with my daughters, then I wonder about the dolphins.... And when I'm here, I worry about my daughters."

Each day during her research trips, she sets out shortly after dawn for the far end of one of the reserve's lagoons. Often, as on this day, she finds mothers and calves. "We think they give birth here, and usually at the beginning of the dry season, which is a good strategy," da Silva says, "since as the water level drops, the fish are easier to find." Mothers and calves stay together for at least three years--a lengthy period, but apparently necessary for the young to learn how to fish and navigate the channels and lagoons.

a Silva motors along slowly until she or Antonio sight a boto. Behind us, two mothers and their calves surface, showing pink beaks and marked fins. "There's Epsilon and her calf, and Horizontal J with hers," says da Silva, quickly making notes. She records the time and date, where she sees each dolphin and if it is alone or with others.

By early afternoon, da Silva has worked her way almost to the junction of the reserve's main channel and the mouth of the Japura--yet she has seen less than half of her botos. "Where is everyone?" she asks rhetorically. From her research, she knows that the dolphins seldom leave the reserve--indeed, this "site fidelity" is one of her key findings about botos. Even those that journey from one end of the reserve to the other eventually return to the lagoon. "Those are the kinds of things we must know--where they stay and for how long, what kinds of habitats they prefer, where they bear their young--if we're to set up adequate reserves," she explains.

On this day, da Silva has seen so few of her big males that she wonders if they've set off on a longer trip (one of her radio-tagged dolphins was reportedly sighted in Peru). But as soon as we leave the Mamiraua's channel and enter the Japura, da Silva spots half-a-dozen large, bright pink males. "Here they are! Here's the party!" she says, laughing, as dolphins surface and blow around us. Within a half-hour, she's counted a total of 30--males, females and calves. "The fishing must be good," da Silva says, speculating that since the Mamiraua's channels are so low, many fish have sought the deeper waters of the river.