Better together: Combining expert and citizen science data improves our understanding of occurrence patterns of lynx and wolves in Lower Saxony, Germany

The return of the two large carnivores wolf and lynx to the federal state of Lower Saxony, Germany, is accompanied by conflicts, which have to be addressed by comprehensive management strategies. Basis for such management is rigorous monitoring of spatial and temporal occurrence patterns of both species. Currently, there are two different monitoring approaches executed in Lower Saxony: the official one, established with the species' return, is based on reporting opportunistic findings by the general public complemented with systematic camera trap surveys and scat searches. The other approach was implemented in 2014 as part of the "Wildlife Survey Lower Saxony", an annual questionnaire sent out to owners and tenants of hunting districts, with the goal to obtain state-wide information on huntable wildlife. In this study, we therefore aimed to compare both monitoring approaches in terms of general, spatial and temporal congruence using an internal classification scheme. We showed that the different monitoring approaches provide similar information on the general development of lynx and wolf occurrence across Lower Saxony. Spatial differences were mainly found at the edges of known distributional ranges. In terms of temporal dynamics, the wildlife survey data seemed to be slightly ahead of the official monitoring programmes. We also found species-related differences, which may be related to different attitudes towards the two species. Overall, our findings indicate that the different approaches complement each other and inferences on species occurrence should be made in conjunction of the two data sets.