Demographic and external drivers of European hare (Lepus europaeus) population dynamics in western Poland from 1960 to 2009

Decreases in the diversity of farmland communities reported at various scales and across taxonomic groups have fueled searches for ultimate reasons, primarily focusing on aspects of agricultural land use. However, the importance of individual external factors as drivers of population dynamics may vary across populations. We used density estimates of the European hare (Lepus europaeus) from a study site near Czempiń, western Poland, covering a time series of 50 years, to analyse long-term trends in overwinter survival. We employed an autoregressive population model to test associations between cereals yields (as a proxy for agricultural land use), fox predation, winter climate and hare density, and compared our results to those reported for a Danish population exposed to an oceanic climate and a Czech population exposed to a more continental climate. We found that at the Polish study site, hare density was negatively associated with fox density, but there were no associations with cereals yield or winter climate. Using generalized additive models, we found nonlinear trends in autumn and spring hare densities also showing a gradual increase in overwinter survival from the 1970s to 2009. We did not detect any decreased juvenile productivity over the study period. We conclude that survival during the breeding season was the most significant demographic trait driving hare dynamics. Our study provides evidence of strong spatial variability in the importance of individual extrinsic factors as drivers of hare population trends.