Costa Rica evaluates the effectiveness of wildlife crossings: connectivity achieved, but collisions persist

In Costa Rica, where roads cross biological corridors and protected areas, researchers from Panthera Costa Rica, with support from the IDB, set out to answer two questions: Do animals use wildlife crossings in a way comparable to how they move through the forest? Do these structures really reduce roadkill?

For six months, underpasses, canopy bridges, and nearby forest sites on national routes 1 and 160 were monitored. 36 species were recorded using the wildlife crossings, but also 74 species were hit by vehicles on both roads.

The research led to the first national monitoring and maintenance protocols, involved more than 400 people in workshops, and brought together specialists from various disciplines.

Main Results

• On Route 160, underpasses were used by 12 species and canopy bridges by four arboreal species. Frequent users included: coyotes, ocelots, black iguanas, and opossums.
• On Route 1, bridges adapted with dry walkways recorded more crossings than conventional culverts, with species like the green iguana and the Mexican porcupine.
• However, species such as the puma, the collared peccary, the margay, the jaguarundi, and the nine-banded armadillo were never recorded using these structures, despite being present in nearby forests.

Mortality and Road Safety

Roadkill remains a serious problem. In six months, deaths of more than 20 species of mammals, reptiles, and amphibians were documented. Route 1 had the highest number of records.

Researcher Araya warned: “The mortality and fragmentation caused by roads is surpassing many of the other impacts humans have generated on biodiversity”.

Additionally, at least 14 collisions with large animals such as tapirs, pumas, and deer were recorded, some resulting in hospitalized people and destroyed vehicles.

Infrastructure and Climate Change

The study concludes that wildlife crossings facilitate movement, but their ability to reduce roadkill depends on an integrated system with exclusion fences, maintenance, and continuous monitoring.

It also suggests that the future of road infrastructure should adapt to climate change, with longer bridges, larger capacity culverts, and dry walkways to increase resilience to flooding.

International Comparison: Argentina

In Argentina, ecoducts and wildlife crossings are vital for reconnecting fragmented ecosystems:

• Misiones: a pioneer in the region, with more than 30 structures, including the Ecoduct 101, the first of its kind in Latin America.
• Iguazú National Park: canopy crossings used by capuchin monkeys and other species.
• Buenos Aires: AUBASA incorporated wildlife crossings on the Buenos Aires-La Plata Highway and plans more on provincial routes.
• Entre Ríos: active projects to install ecoducts and radars in wetland areas.

These structures reduce roadkill, prevent accidents, and avoid the genetic isolation of animal populations.

The study in Costa Rica shows that wildlife crossings are used by multiple species but do not yet guarantee a significant reduction in roadkill. The key is to integrate them into more comprehensive road management and conservation systems.

The Argentine experience reinforces that these measures, accompanied by monitoring and strategic planning, can become essential tools for protecting biodiversity and improving road safety.