The national park contains a large area of Atlantic rainforest — one of the most biodiverse and threatened forest types on earth — and the birdlife is exceptional even by South American standards. Over 400 species have been recorded. Toucans, particularly red-breasted toucans, are common and visible from the walkways; blue-and-yellow macaws fly overhead in pairs; trogons, tanagers, and antbirds work the understorey. Dawn is the best time for birds, before the first buses arrive from both border cities.
Coatis — the raccoon-like animals with long striped tails and pointed snouts — roam the walkways freely and have lost all fear of humans. They are charming at a distance and persistent thieves up close. Do not feed them; the park wardens are emphatic about this, and coati bites are genuinely unpleasant.
The wetter areas of the park shelter tapir, capybara, and caiman. Howler monkeys are heard more often than seen. A good pair of binoculars and a Neotropical bird guide will transform a day at the falls into something considerably richer.