| Summary: | Wolves (Canis lupus) are currently re-colonizing Europe following legal protection, but traffic accidents and illegal persecution may limit further population expansion in landscapes highly impacted by humans by creating local population sinks. We analyzed mortality and disappearance rates of 35 wolves, 2007-2019, by genetic monitoring in the heavily cultivated and densely populated Jutland peninsula. Jutland comprises a Danish part (29 778 km2, 87 people km-2: 12% developed, 61% farmland, 23% forest and heathland) to the north and the German federal state Schleswig-Holstein with Hamburg (16 430 km2, 272 people km-2: 10% developed, 68% farmland, 11% forest) to the south. It connects to the Central European mainland by a 60-km wide stretch of land between Hamburg and the Baltic Sea. Thanks to the geography and frequent genetic sampling, especially in Schleswig-Holstein (mean sampling interval in 2019: 5 days), wolves in the region are registered with high temporal resolution. While immigrants from Central Europe on average stayed 38 days in Schleswig-Holstein before moving on, no wolves returned to Germany upon arriving to Denmark, where they established permanent territories. Wolves in Denmark successfully reproduced in 2017 and 2019. In the German part, annual traffic kill rate estimates ranged from 0.37 (95% CI: 0.11-0.85) to 0.78 (0.51-0.96), whereas no traffic kills were registered in Denmark. Most traffic deaths occurred in a delimited ‘death zone’ around Hamburg. This emphasizes the potential importance of local areas with heavy traffic as regional population drains. In Denmark, most apparent deaths were cryptic, corresponding to an annual mortality (most conservative estimate) of 0.46 (0.29-0.67). With an 87% registration probability of wolves passing through Schleswig-Holstein, and no immigrants returning from Denmark, all or at least the vast majority of wolves that disappeared in Denmark must have died there. The most conservative estimates of annual mortality rates in both Schleswig-Holstein and Denmark exceeded the maximum sustainable harvest rates and total sustainable mortality rates for wolf populations. We therefore conclude the region is a wolf population sink, primarily driven by traffic in Schleswig-Holstein and illegal killing in Denmark. We hypothesize that, frequent encounters between wolves and wolf-averse persecutors in cultivated landscapes may cause unsustainably high mortality rates despite the majority of hunters respecting protection laws. If we are right in this presumption, illegal persecution may be a significant factor, limiting further wolf expansion in West-Central Europe.
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