Abstract 154 – Demographic portrait of the brown bear population in the Western Carpathians.

Nikola Tkáčová, Jana Šrutová, Barbora Černá Bolfíková, Veronika Kornová, Mária
Apfelová, Michal Kalaš, Vladimír Antal, Slavomír Finďo, Marián Hletko, Pavel Hulva

In recent years, ecology has undergone a paradigm shift, recognizing the crucial role of large
mammals including bears, as keystone species. The Western Carpathian population of brown
bear (Ursus arctos) represents a phylogeographic lineage split from the continental lineage,
which differs from populations in the rest of the Carpathians. The Present study aimed to assess
the population size and genetic diversity of this population. A total of 2172 samples were
collected within Slovakia between 2019 and 2021. A combination of non-invasive genetic and
closed model capture-mark-recapture methods was utilized. Eight microsatellite loci and one
sex marker (SRY gene) were amplified, with 48% of genotypes meeting the quality criteria
ensuring sufficient statistical power of the dataset. The Slovak brown bear population
demonstrates a comparable level of heterozygosity (Ho = 0.69) to that observed in regions
characterized by robust conservation efforts and pristine landscapes. The sex ratio was skewed
in favor of females after modeling. Population size estimates were determined using several
approaches, yielding consistent results, and respective hypotheses were tested through
simulation procedures. For instance, employing the TIRM model yielded estimates ranging from
1012 to 1275 individuals. Population density was determined utilizing the resulting abundance
estimates and the total area of confirmed bear occurrence. The resultant value is approximately
10 individuals per 100 km². The effective population size was estimated using the linkage
disequilibrium method to be 144—230 individuals. This value does not exceed commonly
reported recommendations for minimum viable population size, so it is important to consider
also potential future scenarios involving loss of genetic variation due to inbreeding, genetic drift
and genetic erosion.