Species in Peril:
Amazon River Dolphin
Who's ever heard of pink dolphins?
A very varied diet
Of all the toothed whales, the Amazon river dolphin has the most varied diet. It has at least 53 distinct fish species, which are categorized into 19 families. The average size of the prey is 20 centimeters, ranging in size from 5 to 80 centimeters (2.0 to 31.5 in) (7.9 in). The families Sciaenidae (croakers), Cichlidae, and Characidae contain the majority of fish consumed worldwide (tetras and piranhas). The dolphin can penetrate the shells of freshwater crabs and river turtles thanks to its dental structure.
During the wet season, when fish are dispersed in flooded areas outside riverbeds and hence harder to catch, the diet is more varied. When prey density is higher during the dry season, the diet becomes more selective. The dolphins usually eat both day and night.
Their range is restricted
The most common river dolphins are those found in the Amazon. They inhabit a region of around 7,000,000 square kilometres in six South American nations: Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela (2,700,000 sq mi). Waterfalls, like those seen in Brazil’s Xingu and Tapajós rivers, and extremely shallow water define the limits.
One population, known as the subspecies I. g. boliviensis, is isolated in the southern Amazon basin of Bolivia due to a sequence of rapids and waterfalls in the Madeira River. Aside from the Caroni River and the upper Caura River in Venezuela, they are also dispersed across the Orinoco River basin.
The Casiquiare canal serves as the only conduit between the Orinoco and the Amazon. Dolphins are found in river beds during the dry season, but during the rainy season when the rivers overflow, they disperse to the flooded areas, including both the forests and the plains.
In need of help
With a total area of 5,000,000 km2 (1,900,000 sq mi), the Amazon region in Brazil is home to a variety of essential ecosystems. A floodplain, also known as a várzea forest, is one of these habitats and is the habitat of numerous fish species that are vital for human consumption.The várzea also receives a significant portion of its income from overly intensive local commercial fishing. Várzea is made up of murky river waters that are home to a huge variety of organisms rich in nutrients.
The richness of several fish species draws the Amazon River dolphin to the várzea areas of high water occurrences during the seasonal floods. These high-water events are perfect places to pull in the local fisheries in addition to predators like the Amazon river dolphin. For the same fish species, the tambaqui (Colossoma macropomum) and the pirapitinga (Piaractus brachypomus), human fishing activities directly compete with dolphins, leading to planned or incidental catches of the Amazon river dolphin.
Local fishermen overfish, and when dolphins from the Amazon River take the commercial harvest from the nets and lines, it ruins the equipment, compromises the capture, and incites resentment among the fishermen. The Brazilian Institute of Environment and Renewable Natural Resources’ ban on killing Amazon river dolphins is also to blame for the unfavorable responses of the local fishermen, but does not reimburse the fishermen for the harm done to their catch or equipment. The local fisherman either purposefully kill the entangled dolphins while catching the commercially valuable fish, or the Amazon river dolphins get caught in the nets and exhaust themselves to death. The carcasses are thrown away, eaten, or used as bait to draw a scavenger catfish called the piracatinga (Calophysus macropterus).
Since 2000, the carcass of an Amazon river dolphin has been used as piracatinga bait. A market for the distribution of the carcasses of Amazon river dolphins used as bait throughout these areas has emerged because of rising demand for the piracatinga.
A Few More Facts About Amazon River Dolphins
- The Amazon pink river dolphin has the largest bodies and brains of any freshwater dolphin.
- The Amazon pink river dolphin is the largest and smartest out of the five freshwater species
- The Amazon River Dolphin’s brain capacity is 40% larger than humans
Measure up to 9 feet long
Weigh up to 400 pounds
Only breach at the surface
Come in all shades of pink
Watch this video on the Amazon river dolphin, courtesy of BBC Earth
Species Name
Inia geoffrensis
Estimated Population
Approx. 20,000
Conservation Status
Endangered
Range
Amazon River, Surrounding Tributaries
Reasons for Population Decline
Overhunting
Habitat loss
Fishing bycatch
