Monitoring distribution, density and introgression in European wildcats in Switzerland

Monitoring the population dynamics of elusive hybridizing species in human-dominated landscapes helps conservation and management of these species. This is particularly relevant when wild species are potentially threatened by hybridization with a domestic species, as is the case for European wildcats and domestic cats. We estimated the occupancy of European wildcats in 2010 and in 2020, based on genetic analysis of single hairs, systematically collected at 121 1 km2 sites, evenly distributed across the Jura (4307 km2). We mapped the current density of European wildcats in Switzerland based on a spatial capture recapture model using data from 246 1 km2 sites, evenly distributed across the Jura, the Plateau and the Prealps. We estimated the level of admixture between European wildcats and domestic cats in Switzerland in 2010 and 2020. The proportion of occupied sites in the Swiss Jura doubled from 15 % to 31 % within ten years. The current wildcat population size in Switzerland is estimated to be around 1100 individuals. Gene flow from domestic cats into the wildcat gene pool increased from 0.02 to 0.03 migrants per generation between 2010 and 2020. The results suggest that the European wildcat distribution in Switzerland expanded to regions of increased human presence and thus presumably also of increased domestic cat presence. In this context, the threat of introgression of domestic genes becomes more relevant. Thus, continued monitoring of population dynamics using molecular tools is recommended. Long-term systematic genetic survey of population dynamics proves to be an important tool to manage elusive hybridizing mammals.