Covering 180,000 square kilometers (70,000 square miles) smack-dab in the center of South America, Brazil’s Pantanal region is the world’s largest tropical wetland area and home to the highest concentration of wildlife on the continent. Running through this UNESCO World Heritage site alongside the reptiles, birds, and mammals that make the national park a biodiversity hotspot is a 450-kilometer (280-mile) federal highway known as BR-262.
In a new study, researchers asked a simple question: how might this road impact local wildlife populations? To figure it out, they mapped bird and reptile roadkill found along the two-lane paved highway and compared their numbers to a similar dataset surveyed between 1996 and 2000.
The highway itself is found in a region mainly used for livestock with a low human population. Over the course of their survey, the team found 930 animals had been killed, representing 29 reptile and 47 bird species, 20 of which weren’t recorded in the first study 20 years ago. Of the more than 300 reptiles representing 29 species, more than a dozen could not be identified. Of the more than 500 birds recorded representing 47 species, 64 could not be identified. This larger sample of wildlife specimens could mean some species are suffering from unknown consequences that researchers may have never considered.
For example, take the colubrid snake (Hydrodynastes bicinctus). Previous to this survey, it was believed the reptile only lived in the Cerrado plateaus and Amazon rainforest. On the other hand, some species were killed during their reproductive stages and, as the authors note, “such mortality could negatively impact their population sizes.” Reptiles could be particularly vulnerable as they are attracted to paved roads for thermoregulation, keeping their bodies warm at night as roadways tend to store more heat.
The researchers say the diversity of animals killed on the road system is likely “much higher” than what they recorded, leading to long-term effects on wildlife and road safety for both humans and animals, noting it’s important to mitigate wildlife-vehicle collisions by utilizing different strategies, including fences, proper signage, and animal overpasses.
"For managers, the main goal should be to determine target species of greatest concern, focusing on those vulnerable to local extinction or those which represent major risks of serious accidents," said the authors in a statement.
Another paper will present mammal numbers, but the researchers say it’s important to draw attention to reptiles and birds separately.
“Generally, road-killed mammals often involve large animals that cause serious accidents, being the first to catch public attention and concerns about road safety, making highway mortality of other groups, such as reptiles and birds, relatively less reported,” wrote the authors in their paper published in Check List.