Deep in the rainforests of Costa Rica’s Osa Peninsula, monkeys swing through the trees, tapirs wander through dense vegetation, and ocelots move silently through the shadows. It is one of the most biodiverse places on Earth, a living paradise filled with extraordinary wildlife.
But behind this beauty lies a growing challenge. Every day, animals risk their lives when they cross roads that cut through their habitat.
For humans, roads are essential pathways that connect homes, schools, and workplaces. Animals also rely on “paths” through the forest, but these are not random. Wildlife tends to follow habitual routes, much like people repeatedly take the same daily commute to work or school. These movement patterns are learned, efficient, and shaped by the landscape and available resources such as food, water, and shelter. When roads intersect these natural “commuting routes,” the risk of conflict increases. As road networks expand and traffic intensifies, forests become fragmented. This separation can isolate animal populations, reduce access to resources, and weaken entire ecosystems over time, increasing the risk of species decline.
Scientists have long searched for ways to reduce this impact. One of the most effective solutions is wildlife crossings — structures such as underpasses or vegetated bridges that allow animals to safely move across roads. But the key question remains: where should these crossings be built to be most effective?
That is what Dr. Carolina Pinto and her team set out to discover.
Cameras Hidden in the Jungle
To understand how animals move through the forest, researchers deployed hidden camera traps deep in the jungle. These cameras revealed rare moments of wildlife life — animals following trails at night, moving along rivers, or searching for food.
Inhabitants of the Osa Peninsula, captured by Dr Pinto’s camera traps.
The project was not only scientific, but also community-based. Local residents played a key role as citizen scientists, since they know the land intimately. They reported sightings and locations where animals had been hit by vehicles, helping identify dangerous road sections. Their knowledge of the territory was essential, because they are the people who observe wildlife most closely in everyday life.
The team combined these local observations with camera data and computer models that predicted animal movement paths. Together, these tools helped reconstruct how wildlife navigates the landscape, almost like mapping invisible commuting networks through the forest.
Understanding Wildlife “Traffic Hotspots”
The results revealed that animals consistently follow the same forest routes, especially where vegetation still connects both sides of a road. These recurring paths are not random — they are established movement corridors shaped by survival needs, similar to how people repeatedly choose the same safe and efficient routes in their daily routines.
However, some of these crossing points become high-risk crossing zones, places where animals are forced to pass through narrow and unsafe gaps in the forest. These areas concentrate road traffic and wildlife movement in the same space, leading to a higher number of collisions and wildlife deaths.
By identifying these critical zones, the researchers were able to pinpoint where wildlife crossings (such as bridges or tunnels) would have the greatest impact in reducing accidents and reconnecting habitats.
Into the Rainforest: Carolina’s Fieldwork Experience
For Dr. Carolina Pinto, working in the Osa Peninsula was both a scientific mission and a personal transformation.
“The most challenging part,” she explained, “was adapting to the terrain. I came from a different country and was used to flat landscapes, so I had to learn to move through steep tropical forest to reach our camera trap sites.”
Fieldwork was physically demanding. The team crossed rivers with water above their waists, hiked for hours through dense vegetation, and used machetes to clear paths. Along the way, they were welcomed by local farmers who shared meals and fresh natural drinks.
“Everything was a challenge,” Carolina said, “but also incredibly rewarding because of how exciting the experience was.” Arriving during the pandemic made the experience even more intense, but the extraordinary biodiversity of the Osa Peninsula made every difficulty worthwhile.
Article written by Flor Ferreira.
Want to read more about human and wildlife coexistence?
Dr Pinto recommends Crossings: How Road Ecology is Shaping the Future of our Planet, by Ben Goldfarb
Primary paper:
Pinto, C. M., Vargas Soto, J. S., Flatt, E., Barboza, K., & Whitworth, A. (2024). Identifying wildlife road crossing mitigation sites using a multi-data approach – A case study from southwestern Costa Rica. Journal of Environmental Management, 361, 121263. https://doi.org/10.1016/j.jenvman.2024.121263
Other references:
Clevenger, A. P., & Huijser, M. P. (2011). Wildlife Crossing Structure Handbook: Design and Evaluation in North America. https://doi.org/10.21949/1503647
Lodé, T. (2000). Effect of a Motorway on Mortality and Isolation of Wildlife Populations. Ambio, 29(3), 163–166. https://doi.org/10.1579/0044-7447-29.3.163
Luell, B. (2003). Wildlife and Traffic-a European handbook for identifying conflicts and designing 636 solutions. In The XXIInd PIARC World Road CongressWorld Road Association (PIARC).
Van der Ree, R., Gulle, N., Holland, K., Grift, E. van der, Mata, C., & Suarez, F. (2007). Overcoming the Barrier Effect of Roads-How Effective Are Mitigation Strategies? https://escholarship.org/uc/item/66j8095x
Rytwinski, T., Soanes, K., Jaeger, J. A. G., Fahrig, L., Findlay, C. S., Houlahan, J., Van Ree, R. Der, & Van Der Grift, E. A. (2016). How Effective Is Road Mitigation at Reducing Road-Kill? A Meta-Analysis. PLOS ONE, 11(11), e0166941. https://doi.org/10.1371/journal.pone.0166941
Smith-Patten, B. D., & Patten, M. A. (2008). Diversity, seasonality, and context of mammalian roadkills in the southern Great Plains. Environmental Management, 41(6), 844–852. https://doi.org/10.1007/s00267-008-9089-3
Sur, S., Saikia, P. K., & Saikia, M. K. (2022). Speed thrills but kills: A case study on seasonal variation in roadkill mortality on National highway 715 (new) in Kaziranga-Karbi Anglong Landscape, Assam, India. Nature Conservation 47: 87-104, 47, 87–104. https://doi.org/10.3897/natureconservation.47.73036
