Factors influencing mammal roadkills in the agricultural landscape of south-western Poland

Abstract

The aim of the present study was to determine the yearly mortality level and identify the collision places of mammals on a road network with varying traffic volume, as well as to establish the main relations between habitat structure and the number of roadkills. During 26 months of survey on a 48.8 km road network (15 roads) with different traffic volumes (350- 10500 cars per 24 h) situated in an agricultural landscape of SW Poland 383 killed mammals of 23 species were found. The most abundant group were small rodents (40%), with dominant com- mon vole Microtus arvalis (26%) followed by in- sectivores (32%), topped by two species of hedge- hogs Erinaceus spp. (20%). The average (± SD) road-kills index during the whole study period on 11 road sections with the lowest traffic volume (350-460 cars per 24 h) amounted to 0.29 ± 0.14 (range = 0.08-0.56) casualties per 100 m. This value was over seven times lower than on the sec- tion with the highest (10500 cars per 24 h) traffic volume (2.13 casualties per 100 m). Over 80% of victims were found between May and October. During the whole study period 38% of victims were recorded within built-up areas, where 26% of the studied roads were localized. The other 62% were found on the roads situated in the open farmland (74% of all roads). The clear majority of hedgehogs Erinaceus spp., weasels Mustela niva- lis, brown rats Rattus norvegicus, beech martens Martes foina and red foxes Vulpes vulpes died within villages, while the animals killed on roads in the open farmland included all recorded com- mon voles, moles Talpa europaea and common shrews Sorex araneus. The decisive factor affect- ing the mortality level in mammals in the mul- tiple regression model was the daily vehicle traf- fic volume. This variable had significant, positive influence on the number of victims both within the most abundant species, their groups (insecti- vores, rodents, mustelids), as well as all mammals. The road location in the open countryside was an additional factor affecting the level of losses in rodents, while its presence in the built-up area increased the mortality of hedgehogs.