Why Roads Are More Dangerous For Animals Than We Realized

Illustration for article titled Why Roads Are More Dangerous For Animals Than We Realized

Roads are a serious problem for many animals and a leading cause of direct mortality among certain populations. Most of these collisions are unpreventable, but as a rather upsetting study conducted in Brazil shows, many small animals are often deliberately struck by motorists.

Regrettably, a number of species are drawn to roads, attracted to the higher temperatures, lighting, and availability of food resources. Snakes in particular love to hang out on roads, and they do virtually nothing to get out of the way. Accordingly, they take the brunt of vehicle collisions. Moreover, because they're seen as revolting or threatening, they're often killed intentionally.

Ecologist Helio Secco and his colleagues wanted to find out more about this phenomenon. To that end, they set up an experiment along the MG-010 road between Sumidouro State Park and Serra do Cipó National Park in Brazil's Minas Gerais state. This stretch receives upwards of 130 vehicles per hour — but it's also a region rich in biodiversity. Mongabay explains more:

The scientists created fake snakes using sand-filled cloth painted with realistic looking designs. The fake snakes were then placed in different spots on the road, for example close to the edge or close to the median, to judge if vehicles would travel out of their way to run over the life-like snakes. To see if the drivers actually paid attention to what was on the road, the scientists also placed out two liter plastic bottles in similar spots on the road. Then they set up hidden cameras to monitor passing vehicles.

The team was most interested in assessing if drivers would intentionally run over any of the objects placed in the road. The road-kills were only considered intentional if the vehicle changed its natural trajectory in the lane towards the object. Unintentional road-kills, or merely continuing along the same path, were still considered road-kills but were tallied separately.

"There was no difference in the number of intentional road-kills between snakes and control objects," the authors write. "However, we observed that more than half of all road-kills recorded during the study were classified as intentional, making deliberate road-killing a common practice of drivers who travel on Brazilian roads, regardless of the object type." [emphasis added]


Regardless of the object type, they write. Weird. Why the hell do people go out of their way to run shit over?

Also, snakes placed near the center of the road were killed with greater frequency compared to snakes placed at the edge, which the scientists attributed to driver safety. So intentional road-kill happens, but only if it's safe to do so.

The authors of the study write:

Our results can be explained in the following way: intentional snake road-killing on Brazilian roads is not associated with visual identification of snakes on the road. Instead, we believe that when drivers traverse long road sections that require greater travel time, some of them intentionally run over any small object present in the lane. We believe that the frequency with which intentional road-kill occurs varies depending on the road stretch, travel speed, and distance between vehicles. These factors provide different safety conditions for drivers to deviate from their natural trajectory on the lane. [emphasis added]


The researchers conclude: "This study proves that intentional road-killing occurs and that any small object on the road is subject to being struck by a moving vehicle...Thus, we emphasize the need for mitigation measures that prevent small animals, such as snakes, from entering and moving on roads, because drivers tend to intentionally hit any object that is present in the land."

Check out the entire article at Mongabay. And read the entire study at Tropical Conservation Science: "Intentional snake road-kill: a case study using fake snakes on a Brazilian road".


Image: Secco et al, 2014.

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So can this be generalized to other countries, or does it simply make Brazilians look bad?