Even though populations of many large carnivores are expanding throughout Europe, the Eurasian lynx population in the Western Carpathians seems unable to spread beyond the western boundaries of its current distributional range. Many factors, both extrinsic and intrinsic, can influence the potential for range expansion: landscape fragmentation, natal philopatry, low natural fecundity and high mortality, and low and sex-biased dispersal rates. In this study we used non-invasive genetic sampling to determine population size fluctuation, sub-structuring and social organisation of the peripheral lynx population at the Czech-Slovak border. Even though the population size has been relatively stable over the period studied (2010-2016), the individual inbreeding coefficients of residents at the end of the study were much higher than those of founders at the beginning of the study. While non-resident individuals (predominantly males) occurred regularly in the study population, only resident individuals with well-established home ranges participated in breeding and produced offspring. Almost half the offspring detected in the study (predominantly females) settled in or near the natal area. Subsequent incestuous mating resulted in production of inbred individuals, reduction of effective population size of the population, and sub-structuring of the population through formation of two distinct family lineages. Our study illustrates how social constraints, such as territoriality, breeding of residents and natal philopatry of females, lead to incestuous mating in small-sized populations, especially at the periphery of their distribution. This threat should be taken into account in planning of conservation and population recovery of species with similar social structure.

Department of Biology Biotechnical Faculty University of Ljubljana Večna pot 111 1000 Ljubljana Slovenia

Friends of the Earth Czech Republic Olomouc branch Dolní náměstí 38 779 00 Olomouc Czech Republic

Friends of the Earth Czech Republic Olomouc branch Dolní náměstí 38 779 00 Olomouc Czech Republic Department of Forest Ecology Faculty of Forestry and Wood Technology Mendel University in Brno Zemědělská 3 613 00 Brno Czech Republic

Institute of Vertebrate Biology of the Czech Academy of Sciences Květná 8 603 65 Brno Czech Republic Department of Botany and Zoology Faculty of Science Masaryk University Kotlářská 2 611 37 Brno Czech Republic

Institute of Vertebrate Biology of the Czech Academy of Sciences Květná 8 603 65 Brno Czech Republic Department of Forest Protection and Game Management Faculty of Forestry and Wood Sciences Czech University of Life Sciences Prague Kamýcká 1176 165 21 Prague 6 Suchdol Czech Republic

Institute of Vertebrate Biology of the Czech Academy of Sciences Květná 8 603 65 Brno Czech Republic Department of Zoology Fisheries Hydrobiology and Apiculture Faculty of AgriSciences Mendel University in Brno Zemědělská 1 613 00 Brno Czech Republic

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