As part of the joint project ZOWIAC (Zoonotic and Wildlife Ecological Impacts of Invasive Carnivores), a research team from Frankfurt with participation from Goethe University has analyzed hunting data from two decades in 398 German districts. The study aimed to identify the different stages of the invasion of raccoons, originally native to North America, in Germany. The study shows that raccoons went through various stages during their expansion in Germany. A particularly large number of the masked predators can be found in northern Hesse and north-eastern Brandenburg, where their spread has since stagnated. In other regions, such as southwest Germany, the expansion is still in its early stages. The researchers emphasize that their method is not only an effective tool for the management of invasive species in Germany but can also be applied to other alien species in Europe.
To investigate the expansion of the raccoon population in Germany, the research team, headed by first author Dr. Sarah Cunze from Goethe University Frankfurt, analyzed hunting statistics which are regularly compiled by the responsible authorities and are considered a reliable indicator of long-term changes in wild animal populations. In addition to the officially bagged animals, the analysis also included reports of road-killed animals and data from the ZOWIAC research project.
“It has become apparent that raccoons go through different phases during their dispersal – from initial sightings to rapid growth and stabilization at a high level. Our newly developed method makes it possible for the first time to precisely record these dispersal phases at a regional level,” explains Cunze. The analysis shows that the initial expansion “hotspots” were in northern Hesse (e.g., in Kassel) and north-eastern Brandenburg. The data coincides with known historical events. in 1934, two breeding pairs of raccoons were released for hunting purposes near Lake Edersee in northern Hesse. Presumably, additional intentional or unintentional releases occurred over time, which enabled the establishment of a stable population there at an early stage. A second founder population in Brandenburg can be traced back to 25 animals that escaped from a fur farm in Wolfshagen in 1945. “In these regions, the spread of the predominantly crepuscular and nocturnal predators is in a late phase of the invasion, in which population growth is gradually reaching saturation or has already stabilized at a high level and is only subject to natural fluctuations. In other parts of Germany, particularly in the southwest, the raccoon is still in an early expansion phase,” adds Cunze.
“A better understanding of the phase-dependent development of raccoon populations provides the basis for more effective control measures to contain the expansion and reduce ecological damage,” summarizes Professor Sven Klimpel from the Senckenberg Biodiversity and Climate Research Center and Goethe University Frankfurt. “The method offers a practical framework for assessing invasion dynamics and can be transferred to other invasive and alien animal groups and neighboring countries”, he adds. “Our study thus contributes to a deeper understanding of biological invasions and provides valuable insights for more effective conservation planning.”
Publication: Cunze S., Schneider G., Peter N., Klimpel S. (2025) Linking patterns to processes: Using hunting bag data to classify raccoon (Procyon lotor) invasion stages in Germany since the 2000s. Ecological Indicators 175: 113568. https://doi.org/10.1016/j.ecolind.2025.113568
