The Endangerment of the River Dolphin Species

Analeah Vannavong

It has been made official by the International Union of Conservation of Nature (IUCN) Red List that all five of the river dolphin species in the world are now being threatened with extinction. It was recently discovered by the IUCN Red List that the tucuxi river dolphin has joined the register with the other four river dolphin species. 

The tucuxi river dolphin is a species of freshwater dolphin that can be found in the rivers of the Amazon basin and also throughout the rivers of Colombia, Peru, Ecuador and Brazil. It is a part of the Sotalia genus and is known as the “other dolphin” of the Amazon, following the well known Amazonian pink river dolphin. Tucuxi dolphins look similar to the bottlenose dolphin and while their bodies are colored in muted tones of blues and greys, their underbellies are lighter in shades of ivory, grey, or pink. The estimated population of the tucuxi species is unknown, and while some have been seen in larger groups, tucuxi dolphins are typically found in small pods of just a few individuals. This species is extremely sociable and can execute impressive stunts such as spyhopping, lobtailing, flipper-slapping and porpoising; though they tend to steer clear of humans, they generally keep to themselves and occasionally mingle with pink river dolphins.

The widely known Amazonian pink river dolphin or boto, has seen their population fall by 94% since 2000 (EcoWatch 2018). It is considered critically endangered by the IUCN Red List, with an estimated 2,000 dolphins remaining in the Pearl River Delta. They come from the Iniidae family and can be found throughout much of the South American river basin and the neighboring Orinoco river basin that stretches across Colombia, Venezuela, Brazil and Peru. The Amazonian pink river dolphin is much more distinct compared to the other species, because of their long snout and famously pale pink color. They are not actually born pink however, they are born grey and slowly turn pink as they mature. Similar to the tucuxi river dolphin, the pink river dolphin is elusive and typically stays in smaller pods. They are, however the more outgoing of the five species of river dolphins and are often friendly and curious towards humans.

The Irrawaddy river dolphin is another species of river dolphin that is considered critically endangered by the IUCN Red List with an estimated 92 individuals remaining (WWF 2018). These river dolphins can be found roaming the coastal areas of South and Southeast Asia, and in the Ayeyarwady (Myanmar), Mahakam (Indonesian Borneo) and Mekong rivers. These river dolphins have a distinct bulging forehead, are grey in color, have a short beak and between 12-19 teeth on each side of both jaws. They tend to pop their heads out of the water, followed by their backs, so their tails are rarely ever seen.The Irrawaddy dolphin is regarded as a sacred animal in both Khmer and Lao people and the protection of this species is crucial for the overall health of the Mekong river.

Another critically endangered species of river dolphin is the Yangtze finless porpoise which resides in the longest river in Asia, the Yangtze. This porpoise actually shared the same waters with the Baiji dolphin, but that species was declared functionally extinct back in 2006. Additionally, there are only an estimated 1,040 finless porpoises left in the Yangtze, with an annual decline rate of 13% (WWF 2014). Known as the smiling river rarity, this river dolphin also stays within small pods but can be found in larger groups during mating season. They are more timid and weary of humans, so they tend to avoid boats and cruises and it is very uncommon to spot them in the water unless they come to the surface to breathe.

The South Asian river dolphin is the last species of river dolphin that is considered endangered. These greyish-brown dolphins have tiny eyes and a very long, slender snout. Due to their tiny eyes, they are considered blind due to the lack of lenses. But unlike most dolphins, their necks and vertebrates are not fused together so they are able to sweep their heads back and forth while using echolocation to navigate and search for prey. This species is not as acrobatic as the others, typically surfacing the water quickly and not bringing much attention to themselves. They can be found alone or in pairs, and occasionally mingle in smaller pods.

All five species face and share many of the same threats: industrial/agricultural pollution, development projects, entanglement from fishing nets/gear, and dam constructions, just to name a few. These types of threats aren’t just severely depleting the population, but also limiting the species’ range and ability to breed. Estuarine dolphins have a slow birth and growth rate, and a slow reproductive rate, so it’s difficult for them to replenish their population. River dolphins are rapidly disappearing along with their natural river habitats. Understanding the threats that impact them and protecting them ensures the preservation of their unique species and habitat.

Sources: EcoWatch, IUCN Red List, World Wildlife Fund