We gathered information on wolves that were struck by vehicles on roads in Poland from 2003 to 2023, primarily individuals who were killed, but also those (several individuals) seriously wounded that would have died without the intensive help of veterinarians provided in the rehabilitation centers. Data were collected according to the protocol developed by the authors, which included a form to be completed and a checklist for detailed photo documentation. Reports have been provided by the staff of State Forests, officers of regional directorates for environmental protection, the Police, the regional branches of the General Directorates of National Roads and Motorways, Regional Veterinarian Inspections, the staff of companies removing carcasses of animals from roads for utilization, as well as car drivers who found dead wolves on roads.
The photo documentation was sent to us to confirm the species recognition and estimate the individual's age based on the teeth wear. The provided reports contained information on the date and cause of death, the individual's sex, the geographic coordinates of the death site, and the road number and section. Breeding females were recognized based on the evidence of lactation, pregnancy, and nipple length. Reports were verified by the authors and co-workers in the field whenever possible. In cases when doubts appeared, the cause of death was also verified during a necropsy performed by veterinarians or experienced wildlife biologists to exclude instances where wolves were illegally shot and dropped off on the road to simulate an accident. To ensure that as many cases of mortality as possible were registered, we also used an Internet search engine to obtain information on wolves killed and/or injured by cars.
Altogether, we collected data on 447 wolves struck by vehicles from 2003 to 2023; however, the exact locations were known for 441 of these. In six cases, the wolves were found between two neighboring roads; therefore, it was impossible to determine the precise location of the accident. We were able to distinguish between adults and juveniles for 436 individuals and assess their exact age based on tooth wear for 362 individuals. Additionally, we obtained information on sex for 403 individuals. We assigned every killed wolf to the Carpathian, Baltic, or Central European wolf management units/subpopulation (see Linnell et al., 2008, for the justification of management units’ delimitation), taking into consideration the results of a study on the wolf genetic structure (Szewczyk et al., 2019, 2021).
For all individuals with known exact locations (n = 442), we obtained the habitat type (forest, watercourse, open land, or urbanized area) adjacent to the accident site and the average vehicle traffic on the corresponding section of the road. In Poland, traffic data are measured every five years and are publicly available on the Polish General Directorate for National Roads and Motorways website (https://www.gov.pl/web/gddkia/generalny-pomiar-ruchu).
The dataset contains the following columns:
Species: common name of the grey wolf Canis lupus, i.e. wolf
N: number of individuals (every entry is for single individual)
Age_category: pup (1-12 months-year-old); adult (≥1 year-old)
Sex: male, female
Breeder: indicates females with visible singns of pregnancy (presence of fetuses) or lactation (extended nipples)
Age: for pups age is given in months, for adults age is given in years
Date: date in format DD.MM.YYYY
Longitude: longitude - a geographical coordinate in format 00.00000
Latitude: latitude - a geographical coordinate in format 00.00000
Population: name of the wolf population, i.e. Baltic, Central European, Carpathian
Road_Category: general category of the road, i.e. forest_road, lokal_road, regional_road, national_road, express_road, motorway
