Protected areas have been important in reducing tropical forest biodiversity loss. Costa Rica has been a model country in protecting forests and promoting conservation. However, many Costa Rican protected areas are surrounded by highly modified habitat and may be losing species, either because they are too small to support viable populations or are too isolated to allow for population connectivity. We used camera traps to study terrestrial mammal and terrestrial bird populations in the Monteverde-Arenal Bioregion of northwestern Costa Rica. We sampled core protected areas and nearby unprotected, fragmented habitats. Of 33 species historically found in the region, we detected 25. However, most species were rarely detected, and only five were found more than once per 30 days of camera time. The most commonly detected species represented major feeding groups, including obligate herbivores, omnivores, and obligate carnivores. Most ungulates were rare and may not have viable population sizes. However, a top predator, the puma (Puma concolor), was commonly detected. Fragmented areas had lower abundance and fewer species detected; a few species were not detected at all, even though some of them were abundant in the core protected areas. We suggest that conservation efforts are protecting some terrestrial mammals and birds, and there is a functioning food web. However, many species are either rare or extirpated, indicating the Monteverde-Arenal Bioregion is a partially defaunated landscape.

Habitat loss and increases in habitat isolation are causing animal population reductions and extirpations in forested areas of the world. This problem extends to protected areas, which, while often well-conserved, can be too small and isolated to maintain species that exist at low densities and require large contiguous areas of habitat (e.g. some large mammals). Costa Rica has been at the forefront of tropical forest conservation and a large proportion of the country’s land area is currently under some form of protection. One such area is the northwest portion of Costa Rica, which is an extremely biodiverse region with several noteworthy national and privately-owned protected areas. However, each protected area is an isolated island in a sea of deforestation. Within Costa Rica’s existing framework of biological corridors, we propose four sub-corridors as targets for restoration and full protection. These sub-corridors would link five major protected areas in northwest Costa Rica, with all of them linking to larger protected areas in the central portion of the country, while impacting a small number of people who reside within the corridors. After natural or active reforestation of the corridors, the result would be a contiguous protected area of 348,000 ha. The proposed sub-corridors would represent a 3.7% increase in protected area size in the region and only 0.2% of Costa Rica’s total land area. Using the jaguar (Panthera onca) as a model umbrella species, we estimated that each current isolated protected area could support between 8–104 individuals. Assuming lack of dispersal between protected areas (distance between each ranges from 8.1 to 24.9 km), these population sizes are unlikely to be viable in the long term. However, the combined protected areas, connected by biological sub-corridors, could support about 250 jaguars, a population size with a higher probability of surviving. Our study shows that focusing conservation efforts on a relatively small area of Costa Rica could create a large protected area derived from numerous small isolated preserves.

No abstract