The Peninsula de Osa

A world treasure

Mangroves along the Golfo DulceThe Peninsula de Osa hosts approximately 50% of the species found in Costa RicaThe Rio Sierpe, near Corcovado, and one of the largest Pacific mangroves in Central America and approximately 2.5% of the species found in the entire world. Located on the south Pacific coast of Costa Rica, the Osa is one of the last truly remote areas in Costa Rica. To the east of the Peninsula is the beautiful and deep Golfo Dulce, one of only four tropical fiords in the world and the only known central Pacific calving ground for Humpback Whales. To the west lies the Pacific Ocean and in the northern corner  is one of the largest Pacific mangroves in all of Central America. Four species of sea turtle nest on the peninsula’s beaches and dolphins are seen regularly just off the shoreline.View of the east slope of the Osa Peninsula and the Golfo Dulce

The interior of the Peninsula contains the largest lowland rainforest and the only remaining Pacific lowland rainforest in Central America. Half of this forest is represented by Corcovado National Park and the other half is in the adjoining Reserva Forestal Golfo Dulce. The Reserva Forestal is the equivalent of a National Forest.

The Peninsula is considered one of the most bio-diverse places on earth. Due to its unusual and early geographic history, the Osa hosts an astounding number of endemic species (species found no where else in the world).
—-and a disturbing number of species that have been classified as “endangered or threatened”!

Just one species from the huge biodiversity on the Osa Peninsula
A poison dart frog in the primary rainforest of the Osa Peninsula, near Corcovado National Park
One of Costa Rica's igunas that can be seen from the lodge

The Species of the Osa

  • 375 species of birds of which one species is endemic and 40 are endangered or threatened within Costa Rica. (Liz and Abraham have now (unofficially) counted just under 400 species here)
  • 3,100 species of plants, 67 of which are endemic to the Osa and 57 species recently reported as new to science
  • Of these plant species, 750 species are trees and 23 are endangered or threatened
  • Of the 124 species of mammals, 13 are in danger of extinction
  • 6,000 species of insects
  • 117 species of amphibians and reptiles. 14 species reported with threatened populations and 6 are endangered, including four species of sea turtle.
  • 40 species of freshwater fish, of which nine are endemic to the Osa

Note: Many of these figures are approximate and over 10 years old. There are many species as of yet undiscovered or unstudied and species counts vary slightly from source to source.

Figures from “Area Biodiversidad del Area de Conservation Osa” Opinion Ambiental, Oct 2001 by Randall Garcia, INBIO, “Costa Rica Natural History” edited by Daniel Janzen 1983,  “Especies de Flora y Fauna Silvestre con Poblacions Reducidas y en Peligro de Extinción”, 1998 Juan Rodríguez Ramírez and Jorge Hernández Benavides),  Introductory Field Guide to the Flowering Plants of the Golfo Dulce Rain Forests, Costa Rica, 2002, Regenwald Der Osterreicher.

A Preying Mantis, a unique insect that can be seen in Reserva Forestal Golfo Dulce
There are many mammals, both large and small, that can be found on the Osa Peninsula and Corcovado National Park
A bizarre Katydid that is found in Costa Rica's forests