Challenges to reduce roadkill numbers in the Brazilian Cerrado

Estimations suggest that a vertebrate is killed every 15 seconds in the Brazilian roads. Specifically, for the Brazilian Cerrado, the second largest biome of Brazil and classified as a biodiversity hotspot, studies have demonstrated that the overall number of road-killed vertebrates ranges between 0.01 to 0.09 animals per surveyed kilometer. Some astonishing data comes from the capital of Brazil, where a study conducted by the local environmental agency on road sections delimiting five protected areas of the city demonstrated that, over five years of study, 5,355 individuals form 191 different species were killed on the roads.

Novel data recorded at one of the roads that surrounds the second largest integral protection conservation unit of the city, the Águas Emendadas Ecological Station, revealed that the number of road-killed vertebrates remains at a very high level and worst, continues to increase. In two years, a total of 357 vertebrates from 57 different species were found dead on the road. Birds were the most affected group comprising 50.4% of the records, followed by mammals (23.5%), reptiles (15.7%) and amphibians (10.4%).

The blue-black grassquit (Volatinia jacarina) was the most commonly road-killed species with 68 records, followed by the Wagler’s worm lizard (Amphisbaena vermicularis) and the little nightjar (Setopagis parvula). Complementary studies conducted in the same area suggest that the road may be also affecting different aspects of the breeding ecology of the blue-black grassquit.

The blue-black grassquit breeds during the rainy season in Central Brazil. During this period, males become highly territorial and defend very small territories. Preliminary data demonstrates that males have a higher chance of being road-killed than females. Moreover, females nesting near the road produced fewer eggs in comparison to those nesting further away from the road.

Currently, some mitigation measures have been implemented on the road to reduce wildlife mortality. The local environmental agency has installed wildlife fences and underpasses crossing structures. Anecdotal observations demonstrate that they may help reducing accidents for some vertebrates. Snakes and armadillos have been observed not being able to transpose the fences, turning back to the reserve.

While these initiatives may have a great impact on the protection of the fauna, aspects related to human behavior may still be the biggest challenge to overcome. Besides some drivers’ attitude, who has already been demonstrated to intentionally drive over animals, reducing the number of roadkills also relies on changing the behavior the local population by demonstrating the importance of such conservation measures. A recent event could illustrate this problem, some sections of the wildlife fences were stolen from the area shortly after they were installed

Further studies are still necessary to understand to what extent the implemented mitigation measures are effective for most terrestrial vertebrates found in the area. Moreover, if they have any positive effect on bird species, the main affected group. Thus, long-term monitoring is still needed to help measure changes in roadkill number in response to mitigation measures.