Size: 300 hectares of land; 5,800 hectares of sea
Distance from San José: 311 kilometers
Dry season: January through March

It has archaeological importance, apparently having served as an offshore burial ground and ceremonial site for people of the Diquis cultural group who inhabited the Golfo Dulce until the arrival of the Spanish. Besides tombs, the evidence for this consists of large stones spheres found out in the open in many places. They range in size from 7.5 centimeters to almost 2 meters in diameter and their significance is unclear, but the nearly perfect spherical form they possess must have been quite a chore to produce with primitive tools.

Caño Island is a site of pre-Columbian cemetery that is of enormous archeological value. It is still possible to see some of the perfectly round spheres made by the former native Indian peoples.

The island rises to a fairly wide plateau some 90 meters high, which is covered with very tall evergreen forest. The predominant specie is the cow tree which grows up to 50 meters high. It is also known as the milk tree because of the white latex it exudes which can be drunk like milk. Other species of giant trees are the locust, wild fig. Some of the smaller trees that grow on the island are the wild cocoa, rubber tree, Pentagonia gymnopoda, and Caseria aculeata, which characteristic because of its beautiful large thorns.

This island was used as a Indian burial site, and the plant life of the island today is what is left of an orchard planted by the native Indians with these trees. The cow tree has large edible seeds and it would seem that it was planted here to protect its from raids by parrots, collared peccaries and rodents which abound on the mainland.

The insect population of the island is limited to 5 species of beetle, 4 of butterfly, 2 of moth, 7 of bees, and several of ants and other insects.

The marine life in the tide pools is more varied. In addition to innumerable fish, there are large populations of brittle star, and urchins. Clinging to the rocks are shore limpet mollusks, keyhole limpets, which are very abundant, chitons, nerites, and Sally lightfoot crabs, a very populous species of which the exoskeletons can be seen stuck to the rocks. Two species that are in danger of extinction, which are protected by the waters of the reserve are the lobster, and giant conch.

The island is surrounded by five platforms or low coral reefs there you will find 15 species of stony coral. The Porites lobata is the most abundant specie, which grows all over the reef in large colonies. So you can find most of the species of coral-eaters in this area.

Caño Island is located some 20 kilometers west of the Osa Peninsula. Its highest point is 110 meters above sea level and most of its coastline is made up of cliffs that climb as high as 70 meters. The white sandy beaches are small, no longer than 80 meters and some almost disappear at high tide. At low tide, it is possible to walk along the coast for some distance, following the beaches and a kind of rocky ledge that surrounds a large portion of the island and where innumerable tide pools form. An old lighthouse on the southwestern tip of the island affords a view of the forest and a great deal of coastline from the look-out platform.

Birds seen here: cattle egret, common black-hawk, osprey, brown booby, northern phalarope, least tern, and brown noddy.

Animals found here: gray four-eyed opossum, paca, boa constrictor, brown tree frog, great frog, and transparent tree frog, and several species of rats, bats, small snakes and lizard.