The road is a dangerous place for animals: they can be easily overtaken, which can seriously affect wildlife diversity and populations in the long run. There is also a human economic cost and possible injury or even death in these accidents, while heavier animals get stuck or try to avoid them on the road.
Making roads safer for both animals and humans begins with a simple first step: understanding when, where and how many animals are being driven around. This knowledge can help protect specific species, for example by using warning signs, preventing access to the roads for animals, creating overpass and diving paths, or blocking roads. Wildlife frog death data can also help monitor other trends, such as population dynamics, species distribution, and animal behavior.
Thanks to civic science platforms, obtaining this kind of data is no longer a task reserved for scientists. There are now dozens of free, easy-to-use online systems, where anyone can report wildlife collisions or fatalities, which contributes to a more complete picture that can be used later to inform policy makers.
One such project is the Flemish Animals Under Wheels, where users can register the road homicide they have seen, by adding date, time and location online or by using the applications. The data is stored in the online biodiversity database Waarnemingen.be, the Flemish version of the international platform Observation.org.
Between 2008 and 2020, the project collected nearly 90,000 road homicide records from Flanders, Belgium, which were registered by more than 4,000 civil scientists. Mushroom surveying is only a small part of their earth surveying activities – the multi-purpose platform that also enables the registration of living organisms. This is probably why the volunteers have been involved in the project for over 6 years now.
In a first for science, researchers from Nature Point Study, the scientific institute linked to the largest Nature NGO in Flanders, with support from the Department of Environmental and Spatial Development, began to set more than 10 years of road homicide records in the region analyzed, using data provided by civil scientists. In their study, published in the peer-reviewed journal Nature conservationthey focused on 17 key mammal species and their fate on the roads of Flanders.
The researchers analyzed data on 145,000 km of monitored transects, which led to records of 1,726 mammal and 2,041 bird victims. However, the majority of the data – more than 60,000 bird and mammalian frog death records – were collected opportunistically, where opportunistic data sampling favors larger or more “mysterious” species. Hedgehogs, jackals and red squirrels were the most registered mammalian road homicide victims.
In the past decade, road homicide incidents in Flanders have declined, the study found, though search efforts have increased. This may be due to effective road collision mitigation, such as fences, crossing structures or animal tracking systems. On the other hand, it may be a sign of declining populations among those animals most likely to be killed by vehicles. More research is needed to understand the exact reason. Over the past 11 years, European polar cat frog deaths have shown a significant relative decline, while seven species, including deer and wild boar, have shown a relative increase in recorded incidents.
There appears to be a clear impact of the COVID-19 pandemic on road death patterns for some species. Restrictions in movement that followed probably led to fewer casualties and a decrease in the search effort at the same time.
The number of new observations submitted to Waarnemingen.be continues to increase year by year, with data for 2021 indicating about 9 million. Nevertheless, the scientists warn that those recorded observations “are only the tip of the iceberg”.
“Civil scientists are a very valuable asset in the investigation of wild frog death,” the researchers concluded. “Without your contributions, roadkill in Flanders would be a black box.”