The Forest is made up to four very distinctive types of the Tabonuco,Sierra Palm, Palo Colorado, and Cloud Forests.The Tabonuco Forest type which cover14,106 acres in found from Subtropical Moist, Wet and Rain Forest Life Zones at altitudes of 150m to about 700m above sea level .At lower elevations, this forest is home to large straight trees with enormous crowns which emerge above and form a completely dark canopy.The Yagrumo hembra , or weathervane tree and the Yagrumo macho,or matchwood are also quite abundant. Their leaves move to the rhythm of the breeze showing their silver and gold colors.The Sierra Palm, or Palma de Sierra Forest is associated with all zones occurring in the Forest. Found chiefly on steep slopes and stream beds above 1,500 feet above sea level, it commonly forms almost pure strands of Sierra Palms
.Since 1946 El Yunque has been a Commonweath Wildlife Refuge .
There are120 vertebrate species which include bats,lizards and birds. Also ,15 species of amphibians inhabit the forest,
In the cool streams,small fish,shrimp and crabs are found. Small lizards are common everywhere, while the Puerto Rican Giant Green Lizard, which can grow up to 16 inches in length , is found mostly in the limestone hills.Bats are the only native species of mammals found in the forest,though the introduced mongoose and rat are also residents. Various land snails thrive in the heavy rainfall of El Yunque . Spiders, centipedes,butterflies and a variety of insects add to the diversity of the fauna.
There are 16 species of tree frogs in Puerto Rico but only two produce the special co-kee sound which has become a symbol of all tree frogs in the Island. Some call to defend their territory, others are made by mating male to discourage other males from attracting females .The Coqui does not go through a tadpole stage. The female lays 28 eggs and at the end of the incubation, tiny froglets, replicas of the adults, emerge.Coquis living in the coastal lowlands are tree-dwellers: those living in the highlands live mostly on the ground
The Puerto Rican Boa (Epicrates inomatus) is among the snakes that inhabit the forest, although it is seldom seen. A non-poisonous snake, it is hunted for its oil used as folk remedy. It is the largest native species of snake, growing to over 6 feet in length. There is ongoing research to decide whether the Boa should be considered endangered or not at this time. Everything in the forest is protected.