A quest to save South America's freshwater dolphins
Biologists comb the continent's major rivers, counting mammals threatened by deforestation, pollution, and fishing.
Ichilo River, Bolivia
The cloudy waters of the Ichilo River run swift but shallow through Bolivia's tropical Amazon basin. Six biologists perched on the roof of an observation boat peer out onto the creamy brown waters waiting for the first powder-pink sign of one of the most threatened mammals in the world: the freshwater dolphin.
"Sighting," yells one of the biologists, pointing over the bow. A burst of excitement takes over the boat, cameras trained on the spot where the dolphin might resurface. There is a swell in the water and the dolphin's elongated pinkish-grey nose breaks the surface. A graceful curve and he plunges back into the water.
The expedition of Bolivian, Colombian, and Argentine scientists is part of a year-long census of freshwater dolphins in the Amazon and Orinoco river basin. The study aims to measure the health of the rivers by sizing up the population of dolphins, or , as they are known here locally.
South America's river dolphins aren't as sleek as their marine cousins. Rather than a dorsal fin they have a dorsal hump and an elongated beak. But their coloring is eye catching. can range from shades of pink blush to flamingo fuchsia, depending on their physical activity. Conservationists are counting on the to act as a sort of poster child for South American rivers under threat from pollution, overfishing, and deforestation.
"Dolphins are an emblematic species," says Saulo Usma, coordinator for fresh water programs in Colombia for the international wildlife conservation group WWF, which is funding the research. "By studying the dolphins we are collecting information for the conservation of entire ecosystems."
South American pink dolphins are thought to be descendants of marine mammals that migrated into the Orinoco River from the Atlantic Ocean about 50 million years ago. About 100,000 years ago, another species – the gray marine dolphin – is believed to have adapted to the Orinoco and Amazon.
Colombian conservation biologist Fernando Trujillo has been studying these aquatic mammals for nearly 20 years. He has seen thousands of pink dolphins but still gets excited every time he spots one. "Sighting, starboard, two individuals," he shouts, peering through a camera while waiting for the dolphins to resurface.
"I love being alone in a small boat and being surrounded by dolphins, I close my eyes and breathe in their breath. It's fetid, like rotting fish, but I love it," he says.
The benefits of a census
Dr. Trujillo, director of the Colombia-based Omacha Foundation, is the ideologue behind the five-nation census of dolphins along the Orinoco and Amazon River basins. Working with colleagues in Peru, Ecuador, Venezuela, and Bolivia, he and his team have logged more than 1,850 miles on the rivers since the survey began last year. Brazilian researchers, who did not participate in the census project, have been working on separate abundance estimations. The biologists hope to pool their data next year.
The information will help them to establish a baseline population of the dolphins and develop a conservation plan – not just for the mammals but for the entire ecosystem in which they live, Trujillo notes. "If dolphins start to disappear from rivers it means something is happening to the fish and the river itself," he says.
A similar survey is being conducted in Asia, where different species of river dolphins live, though just barely. The baiji dolphin in China's Yangtze River was declared extinct last year, and those of the Indus, Ganges, and Mekong rivers are on the endangered list.
Hope remains, though, for the river dolphins of South America where huge development projects are still on the drawing boards. The major threats for the moment are habitat change due to deforestations, pollution from gold and other mining, and getting caught in nets of local fisherman.
Historically, the has been spared human persecution because of beliefs that it has special powers. Riverside communities tell tales of women impregnated by dolphins or how each dolphin is an incarnation of a man.
A plea to spare the dolphins
Today however, fishermen increasingly view them as an unwanted competitor for fish. All along the Ichilo river, fishermen in wooden canoes cast their nets hoping to catch pacú, surubí, or sábalo to sell on the local market.
Before setting out on the expedition, Trujillo and Belgium-born biologist Paul Van Damme, director of the Bolivian conservation group Faunagua, explained to a group of fishermen in the town of Puerto Villaroel what the trip was about and how the could eventually bring much-needed income to their communities through ecotourism.
Fisherman Fortunato Vargas was unconvinced by the sales pitch. To him, dolphins are a nuisance. "When one gets caught in our nets, it eats half of our fish, and the best ones, too. Of course we get angry. So we kill it," he says, adding that the dolphin can be used as medicine.
Conservation biologist Enrique Crespo, the Latin American coordinator of the Whale and Dolphin Conservation Society, accompanied the team of scientists on the Ichilo expedition. Once the count is complete, he says, the difficult work will be agreeing on a conservation plan that takes into account the needs and attitudes of the people who live side by side with the dolphins. "Science is science, conservation is about politics," he says.
Here on Bolivia's Ichilo River, Trujillo and his team of Bolivian and Colombian biologists were pleased with their results and pleased to see little human impact on the area. In over 550 linear kilometers, they sighted 485 dolphins.
Other countries show more alarming figures. "Ecuador was troubling," says Trujillo. In seven days, only 33 pink dolphins were spotted. And in Colombia they found dolphins poisoned with mercury, apparently from eating fish downstream in Venezuela contaminated by gold mining operations along the Orinoco River.
"The threats that the species faces in both [the Orinoco and the Amazon] watershed are the same, though in some countries they are stronger than in others," says Trujillo.