The majority of El Yunque’s wildlife falls into three categories: birds, reptiles, and amphibians. There are more than 50 species of birds in the forest; the rarest and most beloved is the Puerto Rican parrot, which is classified as endangered. In 1987 an extensive program was initiated to try to bolster the population, though its success has been limited so far. Today there are about 35 Puerto Rican parrots living in the Caribbean National Forest. You’re highly unlikely to spot one, but just in case, keep your eyes peeled for a foot-long, bright green Amazon parrot with blue wing tips, white eye rings, and a red band above its beak. When in flight, it emits a repetitive call that sounds like a bugle.

Other species of birds found in El Yunque include the sharp-skinned hawk, the broad-wing hawk, the bananaquit, the Puerto Rican tody, the red-legged thrush, the Puerto Rican lizard-cuckoo, the green mango, the Puerto Rican emerald, the Puerto Rican woodpecker, the elfin woods warbler, the Puerto Rican bullfinch, and the stripe-headed tanager.

Even more beloved than the Puerto Rican parrot is the tiny coqui tree frog. There are 16 varieties of the species on the island, 13 of which live in El Yunque. You’re only slightly more likely to see a coqui than a Puerto Rican parrot, but you’re sure to hear its distinctive “co-QUI” call, particularly after a rain or at dusk. Even more elusive is the Puerto Rican boa, a nonpoisonous snake that reaches lengths exceeding six feet.

Probably the most likely creature to be spotted in El Yunque is one of its many species of lizards. They are as common as ants at a picnic. The large Puerto Rican giant green lizard, which can grow as big as a cat, is commonly found along the limestone hills, and the smaller anoli, of which there are eight species, are ubiquitous.

The only mammals native to Puerto Rico are bats, of which there are 11 species in El Yunque. But rats and mongooses have been introduced to the island and now live in the forest. The rats were inadvertently brought over on trade ships and thrived on the island’s sugar plantations. The mongooses were imported in a misguided attempt to control the rat population. They are vicious creatures and carriers of rabies, so give them a wide berth if you encounter them.