No one knows for sure, but there are about 300 species of birds in the reserve. Tanagers, Hawks, Eagles, Parrots, Owls, and Toucans are only a few. Over a dozen species of hummingbirds whizz around throughout the forest, some only an inch long. The stunning Andean Cock-of-the-Rock, the Toucan Barbett, and the colorful Golden Headed Quetzal make their home here.

Encompassing thousands of species, the invertebrates dominate the faunal biomass. In Los Cedros there are over 900 species of nocturnal moths, most with amazing wing patterns and colors. There are also thousands of species of butterflies, ants, beetles, spiders, and bees. Often seen is the Pepsis Wasp (hercules wasp), and it may be dragging a tarantula home to serve as a living nest for it’s young. The largest cockroach in the world lives here, along with the first aquatic cockroach found in South America . The reserve is also home to several species each of snakes, lizards and frogs which are often seen, but have been little researched.

Evidence in the form of scat, tracks, and the occasional sighting provide the assurance that our five species of felines roam their territories here in the reserve. Common names are the Jaguarundi, Margay, Oncilla, Puma, and Jaguar. In the morning, along with the chorus of birds, you are likely to be woken by the Mantled Howler Monkey. He is the loudest, so can often be heard, and sometimes seen, in the canopy. The two other primates are the White-Throated Capuchins and the rare Brown-Headed Spider Monkey. The only species of South American bear, the Spectacled Bear, inhabits the higher elevations of the reserve and is seen on occasion.

In the morning, along with the chorus of birds, you are likely to be woken by the Mantled Howler Monkey. He is the loudest, so can often be heard, and sometimes seen, in the canopy. The two other primates are the White-Throated Capuchins and the rare Brown-Headed Spider Monkey. The only species of South American bear, the Spectacled Bear, inhabits the higher elevations of the reserve and is seen on occasion.Other mammals include the Opossum, Nine-Banded Armadillo, Kinkajou, Tayra, Southern River Otter, Collared Peccary, Red Brocket Deer, Paca, Agouti, Spiny Pocket Mouse, Bicolo-Spined Porcupine, Western Dwarf Squirrel, and Red-Tailed Squirrel.

Abundant tree species include Copal, Madrono, Avocatillo, Strangler Fig and Podocarpus, while the Cedars that give the reserve its name are less numerous. Fifty more trees have been identified, but this represents only a small fraction of the diversity present in the area. The dense forest floor and understory is a thick web of buttress roots, lianas, vines, prop roots, drop roots, and decomposing plant material.Characteristic of a cloud forest, the trees on the ridge lines are more stunted in size and laden with masses of luxuriant ephiphytes, with a more open canopy allowing a thicker and richer understory.

Also strong through the upper story are climbing philodendrons, bromeliads, heliconia, and cyclanthaceae. The area is especially rich in orchidaceae, with 190 species identified, with a predicted (by Cal Dodson) 200 yet to be discovered.