Carara National Park contains more primary rainforest than the relatively close Manuel Antonio National Park. As such, it is more humid than the more popular Manuel Antonio National Park, and has denser tree growth and more mosquitoes and other insects. The dense tree growth makes Carara a haven for many bird species.
In Carara National Park you will find: scarlet macaws, manakins, antbirds, orange-chinned parakeets and other parrots, hummingbirds, woodpeckers, jacamars, motmots and the black-throated trogons, anhingas, egrets, kingfishers, and some species of herons.
Carara Park is really close to Tarcoles River (only 5 minutes by car), so you can also find some reptiles like the american crocodile, several snakes, frogs and lizard species.
After or before visiting Carara Park, depending on the tide, you can go for a boat tour on Tarcoles river for an encounter with an american crocodile.