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ŠUMARSKI LIST 11-12/2021 str. 24     <-- 24 -->        PDF

The total effort of lynx recording by camera traps at 182 locations was 31710 camera-trap days or on average, camera traps were active at each location for 163.13 days. Those camera traps recorded 687 lynx events, while 117 records were obtained from other sources.
During the 2018 - 2019 season we identified 39 adult lynxes based on both sides of the body, while additional ten individuals were identified based only on the left body side and 13 based only on the right body side. We identified 21 females and 14 males, while sex could not be identified for 27 animals. If we assume that none of the animals photographed only from the right side matches the one photographed from the left side, then the maximum number of adult animals identified in the season 2018 – 2019 was 62. However, if all 13 lynxes photographed only from the right side match the animals photographed only from the left side, then the minimal number of identified lynxes was 52.
During the 2019 – 2020 season, we identified a minimum of 69 and a maximum of 82 adult animals; 50 lynxes were identified based on both sides, while additional 19 individuals were identified based only on the right and 13 more based only on the left body size. We could identify 24 females and 19 males, while for 39 individuals sex could not be determined. Out of 82 individuals identified in 2019-2020 season, 36 (43.9%, 35 adults and one kitten) of them were already known for the season 2018-2019.
We identified a total of 89 – 108 different adult animals during both seasons. Out of those, 61 were identified from both sides, 28 from the right and 19 only from the left flank. Among 108 adult individuals there were 29 females, 22 males and 57 animals of unknown sex. A total of 30 animals (27.8% out of 108) were observed only once, while three lynxes with the highest number of observations were observed 46, 21 and 20 times.
We compared the identified animals with data from Slovenia (Fležar et al. 2019), and found that seven animals were recorded both in Croatia and Slovenia.
During the two seasons, we photographed 44 kittens belonging to 25 different litters. There were two cases of females with three kittens, 15 cases of females with two, and we recorded a single kitten in eight cases. Seven offspring from the 2018-2019 season could be identified based on their coat pattern (five based on both sides, two by the right side only). Only one kitten from the first study season was recorded in the second season as an adult individual.
Scientific data on distribution and abundance are the foundation for effective population management (Breitenmoser et al. 2006). Since the reintroduction of lynx to Slovenia in 1973 lynx monitoring in Croatia was mainly limited to the mortality records (Frković 2001). Only in the early 2000s research and monitoring of various aspects of lynx biology and ecology started (Gomerčić et al. 2009; Gomerčić et al. 2010, Kusak 2012). Even though, one of the goals of Croatian lynx management plan for the period 2010 – 2015 was to establish a national monitoring system (Sindičić et al. 2010), this was achieved only in 2018 as combined effort of LIFE Lynx project implementation (Sindičić et al. 2018), lynx monitoring in protected areas (especially National park Plitvice lakes and Nature park Velebit), cooperation with numerous hunting grounds and wildlife monitoring contracts of company Geonatura Ltd. Since at the beginning of this study almost 10,000 km2 was considered as potential lynx distribution area in Croatia (Sindičić et al. 2010), the first challenge of our research was to establish monitoring of an elusive species over such a large area. Weingarth et al. (2015) advise that when establishing monitoring in a new area, a survey should be carried out for as long as possible and then optimize the methodology for future monitoring based on the collected data. Therefore, we established our monitoring system over the entire assumed area of lynx distribution in Croatia with photo traps active throughout the year, to record as many different individuals as possible and get a basic insight into the population demography. Afterwards, based on this data, we can plan the optimal methodology for future lynx monitoring and perform more accurate estimate of population size (e.g. using the spatial capture-recapture model).