Estimating the population density of Eurasian lynx in the Ukrainian part of the Chornobyl Exclusion Zone using camera trap footage

The study reports the first estimation of the Eurasian lynx population inhabiting the Ukrainian Chornobyl Exclusion Zone (CEZ, 2600 km2) in 2013–2018. Although lynx were once common in this region, anthropogenic impacts reduced their numbers substantially by the 19th century, leaving lynx as only occasional visitors to the area. In 1986, after an accident on the Chornobyl NPP, the human population was removed from the areas affected by radioactive contamination, and regular economic activity was stopped there. As a result, a gradual recovery of the lynx population was observed. Assessments of the given study are based on camera trap data obtained from wildlife studies conducted in 2013–2018 over nearly 30% of total CEZ area. The number of locations where the camera traps worked simultaneously ranged from 5 to 89. Lynx was recorded 302 times, including 125 observations of 50 identifiable individuals. The total size of the lynx population was estimated to be approximately 53 to 68 individuals of all sex and age groups. For the identified lynx, sex was defined for 22 individuals: 6 females and 16 males. Eleven of 50 identified individuals were cubs. Over the whole period 6 family groups were recorded, 5 of which were females that had 2 cubs, and one a female with a single cub. Most of the identified lynx (33 of 50) were each recorded in one location only. In those cases when the individuals were repeatedly observed in two or more locations (up to 6), the maximum distance between locations ranged from 1 to 23 km (mean distance = 1.9 km). The density of animals was approximately 2.2–2.7 individuals per 100 km2, which is comparable to other areas of Europe where conditions are favourable for this species. Whilst only a preliminary estimate, our results indicate that 32 years after the Chornobyl NPP accident, the CEZ has one of the highest lynx populations in Ukraine. Conditions for lynx are favourable in the CEZ because it has abundant prey species (roe deer and red deer), high forest cover (more than 63%), absence of a residential human population, no agricultural activity, a low level of disturbance from other human activity, and the area has protected status. The recovery of lynx in the CEZ demonstrates the conservation benefits that even unmanaged re-wilding can achieve.