Amazonian forests and waters shelter the most varied fauna ever known. There are 324 types of mammals, 2500 species of fish (less than one thousand in the Congo basin, the closest rival, only 250 species in the Mississippi River), 1,800 species of birds already identified (1,300 in the Congo forest, again, second to Amazonia).

Amazonia has the largest venomous snake in the Americas, surucucu (Lachesis mutus) over 3 meters long. However, in the forest there are less dangerous snakes than in other regions. Amazing snakes are the nonvenomous Jibóia (Boa constrictor), Sucuris (anacondas) and their relatives, slumberous giants of up to 13 meters long and over 200 kilos. The majority of mammals have night and solitary habits. The traveler may wander days in the woods hearing mysterious sounds, but without meeting any group of animals. However, aquatic birds enjoy their paradise in Amazonia.

The State of Amazonas holds 40 Federal conservation units (UCF) and 34 State conservation units (UCE) (as of October 2008). All these units amount to a total of 39.6 million hectares of protected areas through conservation units, besides the indigenous Lands (TI), considering federal and state units jointly.
 
The State system of Conservation Units, like the National System of Conservation Units, establishes that conservation units are divided into two groups with specific characteristics: Conservation Units of Sustainable Use, which aim at making conservation of nature compatible with the sustainable use of part of its natural resources, and Full Protection Conservation Units, whose objective is that of preserving nature, being admitted only the indirect use of its natural resources.