The aim of the study was to estimate the effect of brown hare Lepus europaeus density, vole abundance and habitat diversity on the occurrence of hares in the diet of red fox Vulpes vulpes during the breeding season in agricultural landscapes. The average number of adult hares found among food remains scattered around the breeding dens of foxes (10-24 a year) was used, and its temporal variation was analysed from 1997-2006 in an area located in western Poland, while the spatial variation was analysed from 21 areas in various regions of the country. Spring hare density, vole abundance index (logarithm of the number of burrow entrances per km) and habitat diversity (number of structural elements per km) were estimated using line transects (20-61 km). In the low hare density area in western Poland (5-10 indiv/km2), the number of hares per fox den was influenced by hare density rather than by vole abundance. In various areas with high hare densities (10-28 indiv/km2), multiple regression analysis showed the positive effect of hare density (R2 = 40%) and the negative effect of vole abundance index (R2 = 24%) on the number of hares per fox den, whereas the effect of habitat diversity index (R2 = 13%) was only close to being significant. In the case of low hare density range (1-10 indiv/km2), the number of hares per fox den decreased with the habitat diversity index (R2 = 56%). Therefore, proper habitat management in agricultural areas should lead to reducing red fox pressure on brown hare, especially in areas with weak hare populations.
Key-words: alternative prey hypothesis, brown hare, habitat diversity, Poland, predation, red fox, voles