Cantão
Cantão is a tropical forest ecosystem located in the central Araguaia river basin, the southeastern edge of the Amazon biome, in the Brazilian state of Tocantins.
Five distinct natural communities, each with its own unique species assemblages, occur within the Cantão ecosystem: Igapós are forests which are flooded for four to seven months every year by blackwater rivers.
The igapós of Cantão begin to flood in December, and by March the water in the forest is five to eight meters deep, and running between the trees at speeds of one and two knots.
Only trees adapted to such extreme conditions grow in the igapós, and the rushing annual floods mean that the understory is unusually open for a tropical forest.
The piranheira tree earned its name due to a further contribution it makes to the aquatic ecosystem: it sprouts new leaves after the peak of the floods, which attract great numbers of caterpillars.
Many mammal species that don't do well on trees or in flooded areas also seek refuge in these forests, which consequently become prime hunting ground for the park's two large terrestrial predators, the jaguar and the puma.
The marshes of Cantão hold a great diversity of plant life, and this becomes evident at the peak of the floods, when vines, shrubs, and floating vegetation flower, covering large areas with a mosaic of color.
In addition, broad mats of Paspalum repens grass and other floating vegetation with roots suspended in the current create a substrate for a very productive aquatic ecosystem.
The roots of the vegetation are shaped so as to act like filters, trapping organic particles brought by the current, and doing so near the surface, where oxygen and sunlight are abundant.
Sandy beaches and mud banks are also the preferred feeding habitat for wading birds like the roseate spoonbill, the whispering ibis, and several species of ducks.
As the years pass, the ever-thickening mass of roots begins to accumulate detritus brought by the floods, and the formerly barren sands turn into soils capable of supporting a greater variety of plant species.
The cecropias fruit year-round, and the dense stands that form in attract a great many frugivores which bring seeds from the surrounding forest.
Over the decades, these seeds sprout and grow, overwhelming the cecropias, shading and stifling the undergrowth, and turning into an igapó flooded forest environment.
During the dry season, prey fish become concentrated in isolated water bodies, providing a veritable feast for predators like the giant otter, the Amazon river dolphin, the pirarucú, and the black and spectacled cayman.
Even jaguars join in the feast, diving into forest pools to catch large fish, or sitting in ambush for them as they pass through the shallow water channels that connect deeper lakes.
Four bird species in the IUCN's red list occur in Cantão: the chestnut-bellied guan, the crowned solitary eagle, the bananal antbird, and the Araguaia spinetail.
The trails give access to five pristine lakes in the interior of the park, where top predators such as black caiman, giant otters, and pirarucú fish can be seen.
It is possible to stay overnight on a platform overlooking one of the lakes, and to ride on a canoe powered by electric motor, which facilitates the watching of wildlife such as hoatzins, waterbirds, and giant otters.
