Sunday 26 January 2014

River Dolphin

Image: LNarimatsu
Ah, the magical dolphin! From the cheeky grin to that sensuously curved tail fin, they are truly made for the sea-faring life. We watch them with admiration and a twinge of envy as they effortlessly carve their way through the ocean and leap into the air from the wake of our bulky, steel ships.

We can only look on with our gangly limbs and aching back, our tedious layers of clothing and the awful tyranny of shaving, waxing and nail clipping. We have wandered the world in search of a place to which we can belong. A place where the roots of the banyan are shaped like ergonomic office chairs and roast beef grows on its branches.

Image: Luciana Christante
Lacking such wonders, we've had to carve our own way through the earth. But our hacking and hatcheting, our cities and roads lack the ephemerality of the simple swoosh of a dolphin's tail. Many is the time that we do indeed look on our works and despair, not because they will crumble to dust one day, but because they may never do so.

And so we watch the dolphins. They need nothing more than a few friends and a leaf to provide them with the purest pleasure. We play with them, we work with them, they help us and we help them. The fact that they sometimes get high on pufferfish (apparently) or partake in a whole range of dubious behaviours (apparently) can be swept under the carpet or at least understood as the dark side of intelligence. After all, empathy can be used to build bridges and forge peace but it can it also be used to come up with the best torture techniques.

Dolphins, though! They're just so...

Image: Jose Hilton Pereira da Silva

Not this time. This time we're looking at the River Dolphins, 5 or 6 species who have eschewed the life oceanic in favour of messing around in the river. The freshwater habitat seems to be a kind of ugly juice for our cetacean friends. I don't think there can be a better advertisement for the medicinal properties of sea salt.

Gone are the sleek lines of the athletic and exuberant ocean species, replaced now with flabby, piggish flesh and tiny, shrewish eyes. As you look at that long, graceless beak and bulbous forehead, you know something has gone badly, badly wrong. Even their dorsal fin has become some kind of lazy, malformed ridge. It looks like one of those pictures they use to show us our future evolution if we keep on watching TV digital online multimedia devices.

Image: ollie harridge
Amazonian River Dolphin (Inia geoffrensis)
or boto
The different River Dolphins each come from either South America, the Indian subcontinent or until recently, China. They all look quite similar to each other, which is to say they're all the same kind of ugly. For a long time it was thought they all belonged to the same family, but more recent research has revealed that they actually belong to three separate superfamilies.

This confusion isn't at all surprising. In fact, even figuring out exactly how many species of River Dolphin exist has been a remarkably complicated affair for quite a while now.

Just recently came the news of a whole new species discovered in South America, the Araguaian River Dolphin (Inia araguaiaensis). People knew about this population of dolphins in Brazil's Araguaian river basin all along, but it took a whole lot of research to ascertain whether it was a subspecies of the Amazonian River Dolphin (Inia geoffrensis) or a different species altogether.

Image: Hrbek et al

As it turns out, the two species diverged from each other 2 million years ago! About the same time the Amazon and the Araguaian rivers split apart.

The Bolivian River Dolphin went through a similar experience a few decades earlier. They were considered a subspecies of the Amazonian for over 100 years before they figured out it was its own species in the 1970's. Even now, not everyone agrees.

All of these South American River Dolphins live in murky waters where eyesight isn't of great use. Their bulbous head provides them with superior echolocation to find prey, while a flexible neck lets them worm their flab through tree roots. That's unlike the ocean dolphins who have rigid necks due to their fused vertebrae.

These are the biggest River Dolphins, occasionally reaching as much as 2.7 metres (9 feet) long. They can be grey, pink, white or a blotchy, diseased-looking assortment of all three. Pink ones especially look like some kind of burrowing creature that only came out of its subterranean tunnel because of the heavy rain and stayed because it turned out to be a river.

There are some cool legends surrounding the Amazon River Dolphin. One is that it turns into a handsome young man at night so it can seduce young ladies, which is a whole other layer of confusion to add to all those frogs who actually handsome princes. Another idea is that making eye-contact with one will give you nightmares for the rest of your life. I can definitely believe that, but it isn't super natural or anything. It's just ugly.

There's one other River Dolphin in South America. It has managed to escape all that species/subspecies madness by being the only River Dolphin that doesn't live in a river! The La Plata Dolphin hugs the southeastern coast of South America, venturing into the Rio de la Plata estuary but not up into the rivers. They're the smallest of the River Dolphins at 1.8 metres (6 feet) long, but 15% of that length may be its gruesome snout. As a proportion to body size, that's the longest snout of any cetacean!

If we just hop over to the other side of the world...

Image: Wikipedia
We find ourselves in the Indian subcontinent. Here we find two populations named after the widely separate river systems in which they live, the Ganges River Dolphin in India and the Indus River Dolphin in Pakistan. They were always considered to be the same species until research in the 1970's indicated otherwise. And then more advanced research in 1998 showed they were same species again. Whoops!

Image: Michelle Pemberton
Skull of South Asian River Dolphin (Platanista gangetica)
or susa
They're rather eccentric in that they swim on their side, with one flipper dragging through the sediment. They also have no lens in their eyes! It renders them almost blind; all they can make out is the basic direction and intensity of light. Finally, the female's snout never stops growing! The male's own stops after a while but the female's just gets longer and longer.

Image: 中国物种信息系统(CSIS)
Chinese River Dolphin (Lipotes vexillifer)
or baiji
And that brings us, finally, to the late lamented Chinese River Dolphin. There were once thousands of them in the Yangtze River, reaching some 2.5 metres (8.2 feet) long and armed with the same bulbous head, puny eyes, toothy snout and dorsal ridge.

Their scientific name Lipotes vexillifer means "left behind flag-bearer" and it was revered in China and sometimes called the Goddess of the Yangtze. An old story had it that the Chinese River Dolphin was the reincarnation of a princess who was drowned by her family for refusing to marry a man she didn't love.

Despite all that, the Chinese River Dolphin population declined from an estimated 6,000 in 1950, to none at all in 2006.

The reasons for this steep decline are manifold, from some hunting early on to pollution, loss of habitat and shipping interfering with their echolocation. A huge survey in 2006 couldn't find a single one and while there may still be a few individuals lost in those murky waters, there's virtually no chance of there being enough to sustain the species.

It's tremendously sad, especially given that it's now thought that the River Dolphins are the last of a once large and diverse group of cetaceans that were slowly replaced by the familiar, oceanic dolphins of the Delphinidae family. The same move into freshwater habitats that rendered them half-blind and flabby, may also have secured their future in waters those other dolphins couldn't easily follow.

It worked for a while. How much longer those sparkling eyes and chubby cheeks will be with us is, like so much in the world, up to us.


TexWisGirl said...

awww. poor guys and gals!

Joseph JG said...


Crunchy said...

I've always thought of the River Dolphin as that weird cousin the Bottlenose never talks about.

Joseph JG said...

Which is a bit rich for something with a bottle for a nose