Pulsed Resource Events Mediate Fluctuations in Wild Boar (Sus scrofa) Bag Records in Central Europe

Climate change in Europe is leading not only to an increase in temperature but also to a higher frequency of extreme weather events. Knowledge of the cascading effects of climate change along food chains, including mast seeding and the population fluctuations of seed consumers, is therefore essential. In this study, the spatio-temporal patterns of wild boar (Sus scrofa) bag records at the European level (2000-2023, 16 countries) and across 13 federal states in Germany (2000-2023) were investigated. Data from the federal state of Baden-Württemberg (southern Germany) were then analyzed in detail to understand the relationship between mast seeding by European beech (Fagus sylvatica), sessile oak (Quercus petraea), and pedunculate oak (Quercus robur), the number of wild boar shot, the number of wild boar-vehicle collisions, and the temperature conditions during April and May. We detected bi-annual fluctuations in wild boar bag records that were most pronounced and spatially synchronized over large parts of Europe between 2007 and 2012 and between 2017 and 2020. In Baden-Württemberg, warm spring conditions during April and May were associated with intensive mast seeding by both oak species (Q. petraea; Q. robur) and by beech (F. sylvatica). The amount of energy available for wild boar due to mast seeding by these three tree species was counterintuitively negatively associated with the number of wild boar shot (2000-2022) and with the number of vehicle collisions involving wild boar (2000-2022). Between 2000 and 2022, both time series peaked during years without mast seeding. Our results suggest a cascading effect of springtime temperature conditions, via oak and beech mast seeding, on the wild boar populations of Central Europe.