A hotspot for biodiversity and conservation, Ilha Grande is home to at least 110 resident and migratory avian species,[8] including Magellanic penguins and red-ruffed fruitcrows.

The island has been designated an Important Bird Area (IBA) by BirdLife International because it supports significant populations of solitary tinamous, white-necked hawks, red-browed amazons, unicolored antwrens, cinnamon-vented pihas, bare-throated bellbirds, and azure-shouldered and black-backed tanagers.

[8] Smaller animals, such as rodents and carnivores, include gray slender and big-eared opossums, Brazilian squirrel, crab-eating fox and raccoon, red-rumped agouti and the hairy dwarf porcupine.

[8] Several species of bat also inhabit caves on the island, mainly from the Artibeus, Molossus and Saccopteryx genera,[8] emerging at sunset to feed on swarms of flying insects.

Thus, the remainder of the island is subject to stringent development restrictions in order to preserve the natural environment; vehicles are not permitted and roads are virtually non-existent.