The pink dolphin (Inia geoffrensis) is also called “bufeo colorado” in Peru, “encantado” or “boto” in Brazil, or simply “river whale.” With no known natural predators, this ancient, river-dwelling cetacean of the tropical rainforest has many unique characteristics, but is difficult to study and track in its natural habitat.
Where Pink Dolphins Live
Pink dolphins live in freshwater rivers in South America. Specifically, they inhabit the tributaries and floodplains of the Orinoco River and Atabapo River in Venezuela; the Amazon River in Peru and Brazil; and the Beni River in Bolivia and Brazil. They are found in dark water like the Rio Negro, in cloudy water like the Rio Solimões, and the clear water of the Rio Tapajos. They typically feed alone in shallow lakes or flooded forests during the wet season, which seems to be their preference, and they are most active around dawn and dusk.
Researching the "Botos"
Amazon river dolphins, or “botos,” are difficult to study in the wild for three basic reasons:
- The cloudy or dark waters they inhabit make it difficult for researchers to see them.
- Their tendency to remain underwater, showing just the melons of their heads or dorsal fins when surfacing, makes observation and identification difficult.
- Dangers like piranha. A human entering piranha-infested waters to study pink dolphins would likely be attacked by these aggressive fish.
Progress has been made over the past 25 years in studying and tracking pink dolphins. Author Sy Montgomery spent months in the Amazon researching them in the wild for her books Encantado: Pink Dolphin of the Amazon and Journey of the Pink Dolphins: An Amazon Quest. She met and interviewed Dr. Vera da Silva, a scientist with the National Institute of Amazonian Research (INPA) in Manaus, Brazil, and a leading authority on pink river dolphins.
Vera and her late husband, Robin Best, published the first comprehensive studies on the history, ecology and behavior of the species. And Vera was the first to track the botos using radiotelemetry and discover that they do not migrate.
Why Amazon River Dolphins Are Pink
Montgomery and da Silva describe numerous unique characteristics of Inia geoffrensis, including theories about why they are pink. The mammals range from mostly gray, to lighter gray with a pink underbelly, to completely pink. Babies tend to be mostly gray, but may have a pink belly. A dolphin’s individual coloring may be due to various factors, such as age, or the composition and temperature of the water it inhabits. But since these river dolphins often change color on the spot, becoming more pink when more active, scientists theorize that it’s because of increased blood flow to the capillaries near the skin’s surface.
Pink Dolphins Sleep With One Eye Open
One of the most interesting characteristics of this mammal is its ability to sleep with one eye open. This is because, unlike the way humans sleep, the dolphin is resting one side of its brain at a time, with the awakened side functioning to maintain respiration. Unlike humans, where breathing is involuntary, the river dolphin must “think” to breathe, so as a “bottom sleeper” in shallow water, the dolphin will rise to the surface every few minutes to take a breath before sinking back down to continue resting. Montgomery witnessed breaths taken at about 8-minute intervals.
Other Characteristics of Pink River Dolphins
Pink dolphins have characteristics adapted for their unique habitat, which are different from familiar marine dolphins. These include:
- A melon-like forehead.
- A low, narrow hump on the back rather than a dorsal fin.
- Unfused neck vertebrae that allow the animal to bend 180-degrees to navigate the flooded Amazon forest.
- A long beak with hairs, and jaws with a varying number of teeth depending on the river it inhabits. The beak may help it reach into mudbanks to catch its favorite catfish.
- Large front flippers to swim and crawl, which also enable it to swim backwards.
- A diet of a variety of crustaceans and freshwater fish, up to 50 different species from 19 families, including piranha.
- Perhaps the most highly developed sense of echolocation of all dolphins because of the dark, underwater "obstacle courses" it must navigate.
- A more solitary existence. Mother and baby will travel in pairs, often with the baby riding on her back. Small groups of botos may be found at the conjunction of rivers where fishing is good.
Dolphins in Captivity
Scientists and the general public have been able to learn a lot about pink dolphins by observing them in captivity. On February 20, 2002, the oldest pink dolphin in captivity in North America, a male named Chuckles, died at the age of 34 after living at the Pittsburgh Zoo & Aquarium since 1970. Currently, there are no other pink dolphins in captivity in North America, but at the Duisburg Zoo in Germany, an approximately 35-year-old male dolphin named Baby survives his companion, Vater, who at approximately age 46 was likely the world’s oldest captive pink dolphin when he died in 2006. The Aquarium de Valencia (Venezuela) continues to care for its five pink river dolphins: Ulises, Dalila, Artemis, Penélope and Zeus.
Whether seen in the wild or at an aquarium, people who get a glimpse of a pink dolphin from the Amazon will be treated to a rare sight.
[Photo: Pink dolphin named "Baby" at Duisburg Zoo, Germany, courtesy of Claudia Kuster - www.zoo-foto.de]
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