Brazil: The Boto, pink dolphin of Amazonia

23 to 7 millions of years ago, during the Miocene era, Amazonia was partially covered by seawater. Cetaceans were living in this area. When seawater has been definitely out of Amazonia ground, a species would have adapted to continue living in rivers, drawing the Amazonian landscape. This species became the Boto, known also as the biggest pink dolphin of Amazonia.


 

Genus Inia range of distribution
Represented in green, the distribution of Inia g. geoffrensis, also known as the « Boto » (Source of the map)

 

In the Amazonian pond, the water of rivers can have different colors. Some rivers appear to be ochre (sometimes whitish) and derive their color from the big quantity of clay. This is the case, for example, of the Amazon river. We can barely see under the water in this kind of river.
Other rivers, called ‘black water’ derive their color from the huge concentration of iron and decomposing organic materials contained in the water. These rivers are very acid. This is the case, for example, of the Rio Negro. Despite this ‘tea’ color, the water is not unclear and even when it is dark we can see up to 2 meters deep. It is possible to make some very interesting pictures of the Boto. Those photography presented in the article have been made in the dark waters of Rio Negro.

 
 

At the surface, we see the pink color which is a characteristic of the Boto

 
 

In the « tea » color waters of Rio Negro, the dolphin seems to have an orange color

 
 

The Boto, at adult age, measures around 2.80 meters long and weights up to 150kg for the male. The female are generally smaller, measure about 2 meters and weight around a hundred kilos. This dolphin lives exclusively in fresh waters of the Amazon pond.
We can see them in Peru, in Ecuador and Bolivia but more specifically in Brazil.
These pink dolphins are part of the 5 cetaceans species the smartest of the world. They are also very sociable and can be approached from a boat or even under water. The Boto will have an aggressive behavior only if he feels threatened.

 
 

The darkness occurs as depth increases. After few meters deep, it is really dark

 
 

Dolphin sharping the surface with its muzzle

 
 

Unlike the other dolphins, the Boto has a very short dorsal fin in order not to be shackled when it moves under the immersed roots of the Amazonian vegetation. Moreover, its cerebral vertebrae have the particularity of not being brought together, giving the dolphin an incredible flexibility. Thus, the Boto is capable of spinning the head at 90° (an incredible feat for a cetacean), which facilitates its movements when it sneaks between trees in flooded area.

 
 

The Boto’s fin is way shorter than other dolphins

 
 

The Boto uses the echolocation (he has a sophisticated sonar on the forehead) which allows him to hunt and orient himself even in muddy waters. On top of this, the Boto has also whiskers (this is the only dolphin having them). Whiskers are hairs that he has on the muzzle and that are capable of transmitting him surrounding vibrations (it works the same than for the cats’ whiskers).
These advantages enable the Boto to detect and hunt fishes with accuracy even though the visibility is often weak.

 
 

Boto in levitation in the dark waters of Rio Negro

 
 

The scientist disagree on one point: the dolphin’s coloring. Nevertheless, we note that young Botos are grey and that male adults are much more pink than female adults.
The reason of this coloring would come from (it is just a theory) the character of player and warrior of the dolphin. Indeed, the Boto likes playing, arguing and eating its fellow creatures, even more when it is a male dolphin. The result of this behavior is the multiple scars that cover the Boto’s skins. The dolphin’s scar tissue being pink, the Botos take on the fights their characteristic color.

 
 

A Boto and its healed skin

 
 

Playing with teeth

 
 

The reproduction season is different according to the geographic location, but it occurs more specifically between September and December when the water level of the rivers is at the lowest. After 10 to 11 months of gestation, the female gives birth to one baby (the water level is then at the highest). At birth, the little dolphin measures around 80 cm long and is all grey. The Boto mother will suckle its baby for about a year, but he will become independent after 2 to 3 years.
Among the Boto, the sexual maturity is situated between 6 and 10 years old when the female reaches at least 1,60 meters long and the male 2 meters long.

 
 

 
 

The Boto eats essentially fishes. Today, more than 50 fish species have been identified as dolphin food. The dolphin, having a solid jawbone and many teeth, is also able to break the crabs’ and river turtles’ shell to eat them afterwards.
In total, an adult Boto eats around 2,5% of its body mass every day (which means 3kg of fishes on average every day).

 
 

Hunting dolphin

 
 

Although the Boto has a friendly behavior toward the Humans, it is the main protagonist of surprising legends.
One of them, coming from native beliefs but have gone through colonial times up to our time, draws a rather malicious portrait of the Boto. According to this legend, the dolphin is able to go out of the water and take the appearance of humans in order to infiltrate surrounding villages. Not to be revealed, the Boto, that goes out of the water, is wearing a hat. The hat allows the Boto to hide its respiratory vent which is the only part of its cetacean anatomy that remains, when he is out of the water. Thus capped, the dolphin will infiltrate a village, preferably a festive evening when the attention of the residents is at the lowest. The Boto then seduces one of the girls of the village and takes her away to perform the act of love. Afterwards the dolphin goes back to the river, abandoning his victim, now pregnant with him.
From this legend is born the expression « It is again the Boto ». This sentence is used to accuse the « culprit » in case of unexplained pregnancy. The Boto thus became the father of all the children born of an unexplained pregnancy, which greatly reduced its rating of popularity among the inhabitants of Amazonia. « Boto hunts » were sometimes organized by the inhabitants of Amazonia. They were throwing themselves into a hunt for the pink dolphin in order to take revenge for the unexplained pregnancy of a girl or woman of the village.
Other stories exist in Brazilian folklore. Some people talk about attacks of Boto targeting the small boats of fishermen. To protect themselves from dolphins, the fishermen sometimes fix garlic cloves on the boat when they go alone on the river. Finally, in certain regions of Amazonia, a mermaid plays with men by seducing them, then dragging them to the bottom of the river. This mermaid is sometimes considered as the Botos’ queen.

 
 

The Rio Negro mermaid

 
 

Mystical Boto

 
 

The current Boto’s population is estimated up to 100 000 individuals but the survival of this dolphin is now compromised, mainly because of the poaching of which it is the victim.
It happens that the Botos may be put to death by unscrupulous fishermen who use the dolphin’s flesh to lure carnivorous fish from Amazonia, such as the Piracatinga. The Botos, feeding with fishes, are sometimes considered by fishermen as a potential competitor. A Boto that is skating on a fishing zone risks being expelled with harpoon. On top of this, aphrodisiac virtues have been attributed to the Botos’ genitals, unfortunately it can happen that these are hunted to finish in pieces dried on the market stalls. Thus, although this is forbidden, a recent estimation tells that about 7,000 Botos are killed each year.
If we consider the low reproduction rate of the Dauphin, added to the study of the changes in its natural environment, such as the construction of hydroelectric dam, the increasing of pollution in rivers resulting from mining and deforestation, it is easy to understand why the population of Botos decreases year after year. The future of the Dauphin is therefore not « pink ». It is hoped that it will not completely disappear like his Chinese cousin the dolphin Baiji, which has not been seen in his natural environment since 2007.

 
 

Boto family

 

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