Researchers identified 205 species among nearly 29,000 animals recorded in a nationwide database between 2000 and 2022. The species represented approximately 55% of Poland’s terrestrial vertebrate fauna.

“This is one of the major global problems concerning the coexistence of humans and nature. Roads are a huge convenience for us because they allow for quick travel, but they pose a serious threat to wild animals. And we still do not really know how to effectively solve this problem”, says Andrzej Wuczyński, PhD, a professor at the Institute of Nature Conservation of the Polish Academy of Sciences.

Wuczyński co-authored the first comprehensive summary of wild animal mortality on Polish roads, covering mammals, birds, amphibians and reptiles.

The researchers analysed data from the National Register of Road Collisions with Animals, an online portal known as Zwierzęta na Drodze (“Animals on the Road”). The nationwide database allows volunteers to report dead animals found on roads, including information about the species, location and other details of the incident.

The study included 19,000 observations made by 412 people between 2000 and 2022. Because a single report could include several or even several hundred dead animals, the researchers recorded nearly 29,000 individual animals.

Amphibians accounted for the largest share of species recorded as road victims: representatives of more than 77% of the amphibian species occurring in Poland were found in the database. For mammals and birds nesting in Poland, the figure was approximately 50%.

Rare and endangered species were also among the recorded victims, including the European bison, brown bear, peregrine falcon, fire salamander, European pond turtle and Aesculapian snake.

“We have shown that 55% of domestic terrestrial fauna were among the victims, but we are aware that this is only a portion of the actual mortality. We rely on citizen science, not systematic road searches, so we are unable to record all the animals that die”, Wuczyński says.

Mammals and amphibians accounted for the largest numbers of recorded animals killed, followed by birds and reptiles, in an approximate ratio of 8:8:5:1.

The researchers caution that these figures cannot be treated as a direct measure of mortality because some animals are much easier to detect than others. The number of reports increased with the animal’s weight and the length of time a carcass remained on the road.

“A large animal is simply easier to spot, and its body usually remains visible longer than that of a small rodent, amphibian, or bird”, Wuczyński says.

The number of recorded victims also did not correspond directly to the abundance or distribution of a species.

Wuczyński gives the skylark as an example. Despite being the most numerous bird in Poland, only a dozen or so roadkills have been recorded in the database.

“Larks are specialized field birds; they avoid roads and fly rather high, so they die disproportionately less often than their numbers would suggest. However, there are species susceptible to collisions that appear regularly in reports. This is the case, for example, with the robin, which belongs to the so-called forest floor species and often moves low among shrubs, including those growing on roadsides”, the scientist says.

The researchers also found unusually high bird mortality, particularly among robins, on a busy provincial road running along the Hel Peninsula.

“During the spring and autumn migration periods, this narrow, forested strip of land attracts millions of migrating birds, unaware of the danger posed by the road. A single April inspection of the section between Chałupy and Kuźnica revealed as many as 110 dead robins, three great tits, and three wrens. It is difficult to imagine how many birds die annually in this specific location”, Wuczyński says.

Hedgehogs were among the most frequently recorded mammal victims.

“Their defensive strategy, curling up into a ball, becomes a trap on the road”, Wuczyński says.

Amphibian mortality during seasonal migrations is another significant problem. In the short period from March to April, hundreds of animals can die on sections of road crossing amphibian migration routes.

Of the 20 reports submitted to the database that each included at least 100 dead animals, 19 concerned amphibians, primarily the common toad. This species accounted for nearly 80% of all recorded amphibian deaths.

Grass snakes were similarly dominant among reptiles, accounting for nearly 80% of the recorded victims.

“Grass snakes are particularly common victims of road traffic because they venture onto hot roads for thermal regulation, and often freeze when threatened, much like hedgehogs. Hundreds, even thousands, of them die on roads that cross damp and wet areas, which are the main habitats of grass snakes. The sad statistics cited in the publication concern, for example, the Barycz and Pilica River Valleys, and the wetlands of Biebrza National Park”, says the biologist from the Institute of Nature Conservation of the Polish Academy of Sciences.

The researchers say the findings are also significant because many of the observations came from areas covered by legal protection, including Natura 2000 sites, nature reserves and national parks.

“We have documented the sad fact that simply protecting an area does not protect animals from the effects of roads that cross it. This is one of the weaknesses of the current nature conservation system, known worldwide”, Wuczyński says.

The database nevertheless captures only a fraction of the animals killed on Polish roads. The actual number of road fatalities is unknown, but the researchers say it is likely to be very large.

“Estimates from other countries are in the millions; for example, the annual mortality rate of birds alone in Belgium is estimated at four million, in Canada at 13 million, and in the United States at 89-340 million. There is no reason to assume that the situation in Poland is any different. Compared to Europe, we are a large country with vast biodiversity, so the scale of animal road fatalities is difficult to overestimate”, Wuczyński says.

A major obstacle to assessing the scale of the problem is the lack of a nationwide system for collecting detailed information on road deaths involving vertebrates from all taxonomic groups.

The Zwierzęta na Drodze portal is currently the only nationwide system serving this purpose, but its reliance on volunteer observations makes it difficult to determine what proportion of casualties is actually recorded.

There are also local databases maintained by some research units and national parks, as well as two important government systems run by the Police and the General Directorate for National Roads and Motorways.

“The resources of the latter are impressive, but they have inherent limitations: they focus on incidents involving larger animals, resulting in vehicle damage or human injury. They do not document mortality rates for amphibians, birds, or small mammals. Moreover, the police database does not record animal species at all, while the General Directorate for National Roads and Motorways database covers only national roads”, Wuczyński says.

“And yet, over 90% of Polish roads are other types of roads: provincial, district, and municipal. And it is on these roads that the majority of animals die in Poland”, he says.

The researchers are calling for a nationwide monitoring system in which selected road sections would be regularly inspected by trained volunteers.

They propose recording all dead animals, including the species, location, length of the inspected route and duration of observation. Such data would make it possible to calculate average animal mortality per kilometre of road, compare different locations and carry out nationwide assessments.

But the researchers say the main goal should not simply be to count victims, but to find effective ways of preventing collisions.

Animal crossings, including underground tunnels with guide fences for amphibians, can be effective locally, but they are mainly built as part of new road construction projects.

“These crossings are helpful, but they are still few and far between. Many side roads that intersect amphibian habitats lack such protection”, the biologist says.

Overpasses are also being built for large animals, but their high cost means they are constructed only in selected locations. Road fencing can prevent collisions with large mammals, but it also creates barriers and fragments animal populations.

“We cannot cover all of Poland with fences and animal crossings, nor can we fence all roads. This is unfeasible, and besides, it would not protect birds, bats, or small species. These 'little brothers' of ours die in the greatest numbers, and silently. The problem of road collisions with animals remains an open question”, Wuczyński says.

Katarzyna Czechowicz (PAP)

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