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Rivers
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You will probably spend many hours
in dug-out canoes or boats, according to the type of trip that you will
have chosen.
The fauna found in rivers and on their banks is generally easier to
spot than the one living inside the rainforest, since the field of vision
is much wider.
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But you have to look! This can
seem evident, but I still remember a sweet lady who, after having slept
for nine-tenth of the time during a long dug-out trip, complained about
its monotony and the paucity of visible animal life
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What can you reasonably
expect to see?
Many water birds, of course, some of them spectacular such as the
scarlet ibis.
But you will also be able to admire certain birds as they fly across the
river, the slow flight of the macaws, or the comical one of the toucans.
Having very short wings, their flight consists of a series of successive
flappings interrupted by a short dive. |
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The famous freshwater dolphin:
there exists two species:
The Sotalia (sotalia fluviatilis), a small dolphin which is not
specifically a freshwater dolphin but which swims far into the large
rivers such as the Amazon or the Orinoco.
The true freshwater dolphin (inia geoffrensis). It is a primitive
dolphin with a very elongated nose and minute eyes. As all dolphins
do, it finds its position and hunts by sound echo. It only dwells in
freshwater.
To distinguish one from the other, look at their back. The sotalia has
a crescent-shaped back fin whereas the inia's is not well marked and
has the shape of a triangle with a large base.
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The largest of freshwater otters,
the giant otter of Brazil (pteronura brasiliensis) lives in the
Amazon and Orinoco zone.
It is a magnificent 2 meter long animal, counting its tail.
It captures large fish, I saw some eating 10 kg heavy catfish. It is
relatively curious and in places where it is not hunted for its fur,
it can sometimes come quite close to dug-out canoes.
I have been told of cases of "association" between otters
and dolphins to bring fish in. I have in fact seen dolphins and pteronura
swim very close to each other but maybe they were simply over the same
fish shoal.
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The galapago turtle (podocnemis
sp) can be frequently seen in certain places. You will see them
better during the dry season, if there is much sun, they gather on beaches
and rocks.
They can sometimes be seen comically standing in unstable equilibrium
on branches nearly at water level. The large arran turtle (podocnemis
expansa) can weigh as much as 100 kg but it is becoming rare because
it is pitilessly hunted.
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The crododilians
The most common is the spectacled
cayman (caiman crocodilus).
In quiet places, it too likes to bask in the sun but most of the time,
you will have to be content with seeing its bright orange eyes, by night,
in your lamp beam. It rarely reaches 2 meters in length.
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Many reptiles, like galapago and
arran turtles and certain crocodilians deposit their eggs on the river
beaches during the dry season. They dig a deep and well-hidden hole
but, for those who have wide-awake eyes, their tracks on the sand betrays
them.
Usually, when they have found a nest, Amerindians take only part of
the eggs. It is unfortunately not the case with everyone. This plundering
is one of the main causes of rarefaction of certain species. The spectacles
cayman lays its eggs inside the forest, behind river banks. Perhaps
that is why it is so abundant
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One of the best ways to see monkeys if
from the river, after heavy night rains, especially if the sun shines.
The large spider-monkeys (ateles sp), for example, like to dry themselves
at the top of the large trees.
The river banks are haunted
by tapirs, capybaras and pacas.
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And
of course, there are the very many fish species (over 2400 in South America):
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Certain fish are enormous, like the famous arapaima or pirarucu (arapaima
gigas) |
Some sheat-fish (brachiplatystoma
sp) that weigh over 200 kg! Others are superb. A large part of the aquarium
fish sold in Europe originates from the Amazonian rivers, such as the magnificent
"discus" (symphysodon sp). |
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Unfortunately, you will only have an infinitesimal
chance of seeing the Manatee or sea-cow (trichechus sp), this curious
aquatic herbivore. This enormous animal which vaguely looks like a seal has
been decimated everywhere. Furthermore, it is extremely discreet, spending its
days feeding on water hyacinths. In the Orinoco Delta, these plants grow in
such quantities due to the disappearance of the sea-cows that they block out
navigation over wide expanses.
Finally, to go from the animal to the plant kingdom, those who love orchids
will be able to easily observe through their spyglasses certain large light-loving
species, such as the cattleya orchid.
To end with rivers, let us speak of "black
rivers" and "brown rivers".
The "brown rivers" have a muddy
colour for they are full of silt and rotting plants. It is the case of the Amazon
river and the Orinoco, for example.
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The "black rivers" are tea or coffee colour of a more or less
deep hue. They drain white and sandy soil originating from the very
ancient mountain range of the Guyanas. These soils are very poor in
mineral content. The forest grows literally on the platform ground for
there is nearly no fertile layer.
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The coffee colour comes from substances issued by the decomposition
of leaves : phenols and tannins. It may be that these elements represent
a protection against grass-eaters, I say "may" for it is not
known for certain.
One of the hypotheses trying to explain the presence of a strong concentration
of "defensive" chemicals in plants living on this type of
soil is that the latter is so poor that it is more "advantageous"
for the plants to "invest" in protective chemicals. Trees
grow more slowly but are better protected.
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I have somewhat insisted on this
technical point because you will often hear that there are few mosquitoes
near black rivers whereas they abound near brown rivers.
Personally, I am not sure.
I have been devoured on the edges of certain black rivers and I have
set camp in swimming suit on the edge of certain brown rivers.
In general, in the primary rainforest,
there are few mosquitoes, even on river edges. During the dry season,
bivouacs are very pleasant. There are some mosquito rushes when rains
come but nothing compared to what can be encountered in Northern Europe
during the summer!
From time to time, generally after the first rains, there are invasions
of horseflies. This painful situation usually lasts a few days. They
are diurnal and disappear at sundown.
In fact, paradoxically, it is sometimes
necessary to take cover in the forest in order to avoid being stung!
The savannah zones are sometimes infested by minute blood-sucking flies.
In certain places, they are so numerous that one has to protect one's
face with a small mosquito-net. These insects are not found in woodland.
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