A decade of monitoring the critically endangered Balkan lynx in its core area: Insights from spatial capture recapture models

Monitoring the status of endangered species is essential to guide conservation and management measures, especially for populations facing isolation and small numbers. The Balkan lynx ( Lynx lynx balcanicus ), the most endangered subspecies of the Eurasian lynx, survives in the southwestern Balkans with fewer than 50 mature individuals. Obtaining accurate population estimates is challenging for such a rare, wide ranging and elusive species. We used camera-trapping and Spatial Capture-Recapture (SCR) modelling to provide the first reliable density estimates of the Balkan lynx in its core area, Mavrovo National Park and surroundings, over a decade-long monitoring period. Across five sessions, we recorded 176 detections over 9439 realised camera trap nights, identifying up to 10 individuals per session. Despite a low number of recaptures, our multisession analyses reveal a decline in density (SE) over the past decade, from 2.3 (±0.7) lynx per 100 km 2 of suitable habitat in 2013 to 1.2 (±0.4) in 2023. We compared densities estimated independently for each session or as a trend, with and without excluding unsuitable habitat. These findings provide the first robust density estimates for the critically endangered Balkan lynx and confirm concerns about the state of the population. Our results underscore the value of long-term, systematic monitoring to detect changes in population density. While density estimates are comparable to other lynx populations in Europe, the observed decline, combined with the genetic state of the population, highlights the urgent need for enhanced conservation efforts.