Dolphins are normally associated with the open ocean, and rightly so, because that’s where the vast majority of them live. But not all of them dwell in the salty deep.
There are five river dolphin species in all, and one recently extinct version. All of these dolphins are odd-looking in their own right and have specific adaptations that have evolved separately to deal with the freshwater world they’ve found themselves in.
River dwelling cetaceans are thought to have colonised rivers after being out-competed by ocean-going dolphins in the wilds of the cut-throat seven seas.
Here’s a short rundown of some of these oddly shaped, freshwater wonders:
Sadly the baiji, also known as “Goddess of the Yangtze”, is now defined as “functionally extinct“. The baiji only lived in the Yangtze river, and as of 2004 none have officially been seen alive. An expedition to search for baiji in 2006 returned without a single sighting, some video footage which may show baiji was taken in 2007, but it can not be confirmed. The likelihood is that the population is too small to recover even if there are some stragglers left behind.
The Baiji suffered the consequences of industrialization and all the pollution and bedlam that goes with it. The Yangtze is over 1000 miles long and 12% of the entire population of earth live and work in its vicinity. Humans are dirty and water mammals aren’t keen on filth; human pollution in combination with major dam projects put increasing pressure on the poor old baiji.
The South Asian river dolphin is found in the Ganges and Brahmaputra Rivers. These mighty rivers sprawl though Bangladesh, Nepal and Pakistan making this particular river dolphin one of the most cosmopolitan of the gang.
The Ganges River dolphin has a particularly long and pointy snout which is characteristic of most river dolphins. From millennia spent in muddy rivers the Ganges dolphin has developed a crystalline eye lens becoming pretty much blind, maybe only seeing light and dark patches. Like other dolphin species their primary hunting tool is echolocation.
The weirdest thing about the Ganges River dolphin is that it’s the only cetacean that swims on its side. I guess if it’s blind it wouldn’t notice and its friends wouldn’t notice to tell him either.
The species has suffered at the hands of human pollution, lowered water levels and fishing nets and is now considered endangered. They are protected but the occasional unlucky individual is caught by locals who use the mammal’s oil and meat as an aphrodisiac and as bait for catfish. If they were catching them to eat I could understand, but aphrodisiacs and bait? OMG.
The construction of 50+ dams has limited the species’ gene pool which is also thought to be having a negative impact on their health.
This particular freshwater dwelling mammal persists in the Orinoco, Amazon and Araguaia/Tocantins River systems of Brazil, Peru, Bolivia, Ecuador, Colombia, and Venezuela. They’re not considered endangered but at the same time no one is too sure how many of them there are.
Also known as the boto, this river dolphin is the largest freshwater cetacean in the known Universe. The long-beaked boto has non-fused vertebrae giving it much more flexibility than your average salt loving dolphin, this assists them in navigating through submerged forests. Their colour can range from dishwater grey through to carnation pink, which is nice.
The Amazon River dolphin competes with humans for the same fish species, this causes a spot of bother between tribes people and the watery mammals. The species is protected but that doesn’t stop them getting caught in the nets, the humans get jazzed off about it too because they ruin their nets and they don’t even get the benefit of using the beast they caught. Some fishermen do kill the dolphins of course, and they use them as bait to catch the fish they are legally allowed to eat.
I saved the best for last, or the weirdest looking at the very least. I had the pleasure of seeing one of these Mekong dolphins for myself whilst visiting the Mekong delta in Laos, admittedly it was about a mile away, but it still counts.
Unlike the rest of the freshwater dolphins we’ve seen today these guys pretty much have no snout at all, their heads sort of resemble bowling balls don’t they? This odd visage makes sense when you learn that they’re more closely related to killer whales than other dolphins.
The Irrawaddy dolphin moves at a relaxed pace and is thought to capture fish by sucking them into its mouth like a Dyson.
Humans seem to have had a mutually useful relationship with the Irrawaddy for centuries. Fishermen in India remember a time when they would literally call out to the dolphin asking them to herd fish into their nets. Similar stories are reported in Burma so there must be something in it, the dolphins would be rewarded with fish for their services.
An 1879 report indicated legal claims were frequently brought into native courts by fishermen who wished to recover a share of the fish from the nets of a rival fisherman which the plaintiff’s dolphin was claimed to have helped fill.
The Irrawady has a pretty large hunting ground that extends from the Bay of Bengal to New Guinea and the Philippines but there’s not a thriving population, they’re pretty rare and on the decline. Technically they aren’t considered a true river dolphin because they mainly stick to brackish water. I’ve still included them here though because they look so odd.
I’ll leave you with this picture of a finless freshwater porpoise. They’re the only species of porpoise that lives in fresh water and they are super ultra endangered. Each individual that dies is another nail in the coffin of the freshwater porpoise. This photo should NOT be funny, but the corpse’s wry smile tickled me… it’s like he’s thinking “don’t worry, I’ll let her cry for a few more minutes and then I’ll tell her I’m only messing”…
