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 Directorate for 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 identification and to estimate age based on tooth eruption and 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.
The dataset contains 517 wolves. Each location was checked against the road network of the national topographic database BDOT10k (GUGiK); road numbers were corrected where the recorded road did not match the location, and wolves found between two roads were assigned to the nearest road. Every wolf was assigned to the Central European (west of the Vistula River), Baltic (east of the Vistula) or Carpathian (east of the Vistula and south of 50.25° N) population. Traffic volume was taken from the General Traffic Census of GDDKiA (2010, 2015, 2020; https://www.gov.pl/web/gddkia/generalny-pomiar-ruchu), using the census year closest to the year of death.
The dataset contains the following columns:
Record_ID: identifier of the record in the authors' database
Species: common name of the grey wolf Canis lupus, i.e. wolf
N: number of individuals (every entry is for a single individual)
Age_category: pup (< 12 months), yearling (12–24 months), adult (> 24 months); null – unknown
Sex: male, female; null – unknown
Breeder: breeder – females with visible signs of pregnancy (presence of fetuses) or lactation (extended nipples)
Age: detailed age where available; for pups in months, for older wolves in years (based on tooth wear), assuming births in May; 1_year and 2_years – yearlings (12–24 months, i.e. second year of life, which ends in the third calendar year), 3_years – wolves in their third year of life, etc.
Date: date the carcass was found or reported, format DD.MM.YYYY
Longitude, Latitude: geographical coordinates (WGS84) in format 00.00000
Population: Baltic, Central_European, Carpathian
Road: road number (A – motorway, S – expressway, DK – national road, DW – regional road, DP – district road, DG – municipal road); null – unnumbered internal or forest road
Road_Category: motorway, express_road, national_road, regional_road, district_road, municipal_road, internal_or_forest_road
Road_Class: road class used in the analyses – Motorway (motorways and expressways), National, Regional, Local (district, municipal, internal and forest roads)
Fenced: yes – motorways and expressways (fenced); no – other roads
Traffic_AADT: annual average daily traffic (vehicles per day) of the road section; null – no traffic census data (local roads)
Traffic_year: year of the traffic census (2010, 2015 or 2020)
