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River (Fresh Water) Dolphins: Part 2

Apure (* ca. 1957; † 9. Oktober 2006 in Duisbu...

Continued from Part 1:

Let’s start with the Amazon/Pink River Dolphin’s first cousins, the Bolivian River Dolphin.  They live in the same river system (in the Madeira, a tributary of the Amazon), but up a  225 mile (360km) stretch of 18 rapids. I couldn’t find the height of the falls/rapids they are talking about, but this blog post will give you an idea of how much of a drop there is in places.

How did they get there?  National Geographic says that there was a drought about 100,000 years ago that stopped the Bolivian sub-group from mingling with the rest of the Amazon Dolphins.  That would have been some “drought”!

We don’t have to make such speculations since we know these dolphins settled into their current location between the Flood’s peak and the end of the Ice Age.  Having been separated all this time (around 4,000+ years), they are different enough from their downriver cousins to be classified as a separate “sub-species” now.

There are several other River/Brackish Water Dolphins along the South American coast.  The La Plata or Franciscana Dolphin has members in the ocean, in the mouths of rivers around the Southeastern coast and up river far enough to be considered River Dolphins.  They have dorsal fins like ocean dolphins, but long snouts and flexible necks like River Dolphins.

All River Dolphins are at risk of going extinct because their homes are limited to one area, so if something happens to their particular river, they’re stuck!

The Dolphins of South America are not being treated meanly on purpose (except for some stories of fishermen using their meat as bait), but accidents happen when people are around, and you saw in Part 1 how long it takes for a new generation of young dolphins to replace killed ones.

In South America there is bootleg gold mining going on which leaches mercury into the water to the fish. When the Dolphins eat these fish, they get high doses of mercury and can die out in that area.  Of course, mercury in the water isn’t good for people either, so the governments of these places are working to stop this from happening.

The River Dolphins of South Asia aren’t doing so well, though.  The Baiji (Buy-G) or Yangtze Dolphin hasn’t been seen for sure since before 2007.  It looked a lot like the South American River Dolphins but was bluish-gray in color.  Adults could be so pale that they were called the White Dolphin.  Scientists figure that even if a few of these shy animals are still living, there aren’t enough to rebuild a healthy population again. Because of the thoughtlessness and poverty of people along the Yangtze river, we’ve lost another animal to the fossil record.

In Southwest Asia live the Indus River and Ganges River Dolphins. I don’t have room to write more about them, so be sure to follow the links to see where they live. They are also endangered with numbers of only a little over a thousand of each group.

These River Dolphins are known for being very slow swimmers with eyes that have no lenses so they’re almost blind.  So, what they do is swim on their sides at the bottom of the river and open their mouthes when they feel and hear something to eat ahead.  Like other River Dolphins they like fish, shrimp and other crunchy things that live along the river bottoms.

Kratié in Cambodia Irrawaddy Dolphin

Kratié in Cambodia Irrawaddy Dolphin

Besides these groups of properly titled River Dolphins, the Solari (aka Tucuxi, see Part 1) of the Amazon and the Irrawaddy dolphin of South Asia also live in rivers and their deltas.  But these are both classified as part of the group of ocean living dolphins.  In fact, both of these varieties have saltwater cousins.  They have dorsal fins and don’t have extra long snouts like most River Dolphins.

Here are today’s Evolutionist quotes (I promise I’m not hunting for these, they just keep coming up!):  “They [River Dolphins] are perplexing creatures, having both some of the most advanced characteristics of all living cetaceans and some evolutionary holdovers from many eons past.”  From Think Quest

“The ancestor of the Yangtze river dolphin resided in the shallow sea that inundated the Yangtze River Basin during the globally high sea levels of the Middle Miocene period (approximately 20 million years ago).”  From NOAA Fisheries.

They’re quite right, all you have to do is take out about 19.9957 million years!

Check out great pictures in National Geographic’s Photo Article about River Dolphins (and Porpoises)

Plus, the Whale and Dolphin Conservation Society

So is this great and wide sea, wherein are things creeping innumerable, both small and great beasts….  These wait all upon thee; that thou mayest give them their meat in due season.  That thou givest them they gather: thou openest thine hand, they are filled with good.  Thou hidest thy face, they are troubled: thou takest away their breath, they die, and return to their dust. Thou sendest forth thy spirit, they are created: and thou renewest the face of the earth. Psalm 104:25-30

Then said he unto me, These waters issue out toward the east country, and go down into the desert, and go into the sea: which being brought forth into the sea, the waters shall be healed. And it shall come to pass, that every thing that liveth, which moveth, whithersoever the rivers shall come, shall live: and there shall be a very great multitude of fish, because these waters shall come thither: for they shall be healed; and every thing shall live whither the river cometh. Ezekiel 47:8,9

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River (Fresh Water) Dolphins: Part 1

English: Pink dolphin en Singapure

Pink river dolphin

Several years ago, I learned about the Amazon River dolphins (and sharks) while watching a nature program.  It is always fascinating to learn about creatures who live in unexpected places.  What I didn’t learn until much later was that there are more fresh water dolphins around the world (but that will have to wait until next time)!

We’ll start with the Boto, or Pink River Dolphin of the Amazon, since they are the largest group.  As you can see in the picture, some of these dolphins are kind of pink, but they come in a lot of other colors, too.  Young Amazon dolphins are dark gray on top and lighter gray underneath.  Most adult female are a shade of light gray.  Turns out the pink color is from scarring that the males get by fighting each other.  Tell that to your mom and she won’t be surprised.  Tell your dad what color they turn when they scar and he might not be too happy! 😀

channel-billed toucan watches amazon river dolphin

channel-billed toucan watches amazon river dolphin (Photo credit: Joachim S. Müller)

One of the things you’ll notice about most river dolphins is that they don’t have high dorsal (backbone) fins.  I’m sure God made them that way because they would tend to get caught on tree roots and things in their crowded environments. The one river dolphin that does have a dorsal fin is the Tucuxis, Sotalia (aka Gray River Dolphin) which lives near the end of the Amazon and is almost the same as its ocean neighbors.

Another feature He gave the Amazon River Dolphin is that they keep their chin hairs, which all dolphins are born with to help them locate food.  River Dolphins also have longer snouts than their ocean cousins and have larger forehead “melons” which help them to use echolocation to find fish in muddy water.

The Creator also provided River Dolphins with both cone and flat molar teeth (ocean dolphins only have cone-shaped teeth).  This helps them eat a large variety of food mostly over 50 types of fish including piranhas, plus the occasional crustacean or even turtle.

The Amazon River Dolphin is the largest of the freshwater dolphins with the biggest adult measured today 249 cm (8’2″) long and weighing185 kg (407lb)!  Most are quite a bit smaller with the biggest female measuring 216 cm (7’1″) and 142 kg (312lb).  An average female is  only about 1.8m (5′ 10″).  The Gray River Dolphin is even smaller, averaging 1.5 m (4’11”).

A mother River Dolphin only has a baby every 4-5 years.  They carry their babies for about 10 to 11 months before giving birth.  God timed the baby’s coming for May/June so Mom has the most plentiful food when Baby needs her the most. They have single babies that are about 80cm (31in) long and weigh around 6.8kg (15lb) at birth.  Like other water mammals, the mother helps her baby get to the surface to breath and feeds her baby milk for a few months.  The little one doesn’t leave its mother, though, sometimes staying with her for several years.

Males are often solitary, enjoying the bigger prey in the deeper parts of the river. Females tend to prefer the safer back waters where it is shallower until these dry up and force them back into the rivers and lakes until next flood season.  But, a bit like the large groups that ocean dolphins form, River Dolphins sometimes live as a family unit with Dad, Mom and Baby. There have also been sightings of small family groups of dad, mom, baby and older sister living together.

More about other River Dolphins in Part Two!

And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good.  Genesis 1:21 

Other sites I used to research this post:

Whale and Dolphin Conservation Society: River Dolphins

Marine Biology: Amazon River Dolphin