A method for evaluating density of roe deer, Capreolus capreolus (Linnaeus, 1758), in a forested area in Bulgaria based on camera trapping and independent photo screening

We performed an experimental survey of roe deer (Capreolus capreolus) in the Chepino Game Hunting Station (Southwestern Bulgaria) in spring 2014 using a camera-trap network. We established a network with a density of one camera per 2 ha of forest. Traps remained activated for five days in one sampling plot of 80 ha. Camera traps triggered by animal movements were set to take successive pictures with ten-second time lapses. Camera trap records were examined by three independent groups of researchers and allowed for a very high rate of individual recognition (up to 82% of individuals pictured were classified by sex and age class). We identified a minimum of 29 roe deer individuals corresponding to a density of 36 individuals/km2, with a male/female ratio of 0.71, and a fawn/doe ratio of 1.33. This density was surpris-ingly high as compared to the known Bulgarian standards, and indicated a good conservative management of the roe deer population in the Chepino Region. Further, our estimates were confirmed by performing a capture-mark-recapture study of roe antlered bucks which were easy recognisable. We found a detection probability of 0.91 and a population density of 36.25 deer/km2. Therefore, camera networks could be used as a reliable monitoring method to estimate roe deer population density and to get a reliable population structure in areas where alternative monitoring methods are not possible or are too expensive. We recom-mend this method to be adopted by game reserves in Bulgaria in order to improve knowledge about roe deer population demography and for improving the management of its populations.