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

South America's river dolphins are disappearing, but Vera da Silva is out to change that

At about 9 a.m. in the heart of the Amazon, Brazilian biologist Vera M. F. da Silva spots the animals she's come in search of: pink river dolphins, or botos. "Look," she says, standing up in her small boat to get a better view, "there's a big male, XX. He's always here. And there's a mother and calf." On all sides of our boat dolphins are surfacing, their pink heads, long beaks and dorsal fins flashing above the lagoon's dark waters. Like whales, they eject a vaporous spray as they breathe, and they fill the air with their snorting puffs.

For da Silva, who heads the aquatic mammals laboratory at the Institute Nacional de Pesquias da Amazonia in Manaus, it's like being greeted by old friends. For four years she's studied this population of botos, spending two weeks of every month here in the Mamiraua Wildlife Reserve on the Japura River. "They always come to see me," she says with obvious pleasure. "I think by now they know this boat. So they come to look at us. You know: What are those humans up to?'"

Dressed simply in shorts and a long-sleeved blue shirt, da Silva sits with notebook in hand, her dark brown eyes intently scanning the lagoon for a hint of a dorsal fin. When she or her assistant, Antonio, spot one, they watch closely for natural markings or a research brand, such as the double Xs on the big male's fin. The petite, 44-year-old researcher then notes where they are, and what other animals (if any) the dolphins are traveling with.

By collecting this data, the Brazilian scientist is attempting to fill some big gaps in our knowledge about these cetaceans. For example, she notes, "we don't know how long the interval is between offspring, or even how far the botos travel" from Mamiraua. Answering such questions will help da Silva and others devise management plans for the botos. For although the dolphins are not yet endangered, that could easily change. Dams, pollution and overfishing threaten almost all species of river dolphins worldwide (see chart, page 30). "I'm afraid the Asian ones are going extinct," da Silva says, shaking her head. "But we still have a chance with the botos, so we need to do everything we can to learn about them and to protect them."

No one is better qualified to learn about and protect Amazonian river dolphins than da Silva, other experts say. "Vera--with her late husband, Robin Best--made the first rigorous studies of the behavior, ecology and life history" of these creatures, says Randall Reeves, chairman of the cetacean specialist group of IUCN--The World Conservation Union.

What makes botos and other river dolphins unique is that they never leave fresh water. Only four such dolphin species are known: botos, Ganges River dolphins, Indus River dolphins and Yangtze River dolphins. A smaller dolphin in the Amazon, the tucuxi, seems to have both a river and a marine form. In contrast to these few river dolphins, there are 20 genera of marine dolphins, some of which venture into rivers occasionally. Although some of these seafaring dolphins need protection, river dolphins are in worse shape, in some cases from overfishing, but more often from pollution and from dams and irrigation projects that limit their movements and cut off populations.

he pink dolphins' exact population size is unknown. In the Mamiraua alone--which covers more than one million hectares (2.47 million acres)--da Silva estimates there are at least 140; about 700 are thought to inhabit Peru's Pacaya-Samiria National Reserve. They thrive outside these reserves as well, living throughout the Amazon and Orinoco river basins. The botos share their freshwater world with the smaller, speedier tucuxi. IUCN--The World Conservation Union, a worldwide body that monitors wildlife, currently lists botos as vulnerable, while tucuxis are classified as data deficient. "We've made some study of the botos, but we know even less about the tucuxis," says da Silva.

ometimes, while watching the botos surface and dive, we catch a glimpse of a tucuxi. They squirt out of the water in bold, sudden jumps and then vanish, probably in pursuit of a fish. Yet even from these brief glimpses, one can easily see that the two dolphins are different.

Indeed, there is no other dolphin like the pink boto. For starters, of course, they are distinctively colored, varying from a rosy blush to almost flamingo pink. Only the adults are so colored (newborns and adolescents are a bluish-gray)--although scientists are unsure why. "It may have something to do with the onset of sexual maturity, or how active physically they are or how much exposure they have to the sun," says da Silva.

Their color is perhaps their best feature; these are not the elegant, streamlined animals of the deep sea. Rather, adult botos--which average two meters (6.5 ft.) in length--have chubby bodies, lumpy "foreheads" and long, flexible beaks. They're shaped much like primitive dolphins known only from the fossil record--and may even represent a relict species that adapted to freshwater millions of years ago. (The tucuxis, however, are recent arrivals and unquestionably related to today's marine dolphins.)