The flooding season of Solimões river causes a rise in the water level of 10 to 12 meters from the dry to the flooded season every year. The water movement is caused by rains in the river springs of region associated with the annual defrosting of the Andean ice caps. The floods, with the resulting annual sediment deposition, define the floodplain geomorphology, its fauna and flora, its biogeography and even patterns of human occupation. The flood brings a large amount of sediments from the Andean slopes with a high concentration of nutrients. This is the main cause of the huge productivity in Amazonian floodplain, observed in both aquatic and terrestrial system.      

      The fauna observed in environments within Mamirauá is highly endemic. On the one hand, the harsh conditions imposed by prolonged floods every year limit number of species able to survive in such drastic conditions. On the other hand, in the course of time, they allow the emergence of unique adaptations that may define speciation and endemism in that environment. There are about 35 species of mammals, 360 of birds, 79 reptiles and more than 300 species of fish. Primates (9 spp.) are easily sighted in Mamirauá and represent one of its best attractions. The flagship species is the endemic White Uakari Monkey.

       Besides the White Uakari Monkey other wild life in the reserve is Pink River Dolphin, Black-faced Squirrel Monkey, Red Howler Monkey, Brown-throated Three-Toed Sloth, Long-nosed Bat and the Avifauna highlights are Ladder-tailed Nightjar, Horned Screamer, Razor-billed Curassow, Hoatzin, Slate-colored Hawk, Scarlet Macaw, Festive Parrot, Tui Parakeet, Spotted Puffbird, Scarlet-crowned Barbet, White-chinned Jacamar, White-eared Jacamar, Lettered Aracari, Channel-billed Toucan, Ringed Woodpecker, Chestnut Woodpecker, Long-billed Woodcreeper, Black-crested Antshrike, Plumbeous Antbird, White-browed Antbird, Bare-necked Fruitcrow, Masked Crimson Tanager, Yellow-bellied Dacnis and many other species.