Reproductive potential of Roe deer in Slovenia

European roe deer ( Capreolus capreolus L.) is the most important game species in majority of European countries, including Slovenia. Therefore, it is crucial to perform an effective management of this species, which should be based on the knowledge of its population dynamics. Systematic research on reproductive potential (e.g. fertility and potential litter sizes) of roe deer in Slovenia began in 2013. Reproductive organs (uteri with ovaries) of culled roe deer females, i.e. adult does (n = 392) and yearlings (n = 82), were sampled in 45 hunting grounds all around Slovenia during the hunting season, from 1 September to 31 December 2013. Fertility was determined by the presence of corpora lutea in ovaries, and potential litter size by counting their numbers.Results confirmed high fertility of roe deer females in Slovenia. Corpora lutea were present in ovaries of all except two adult does, and only 15.9% of yearlings was infertile, all of them in poor body condition (undressed body mass <11 kg, i.e. without abdominal content, but with head and legs retained). Potential litter size (number of corpora lutea in ovaries) was primarily influenced by doe body mass and age. Mean number of corpora lutea was 1.84 in adult does, and 1.20 in yearlings, respectively. Body mass has a strong positive impact on the potential litter size in both age classes. However, yearlings (primiparous does) perform much higher variability in reproductive potential (i.e. all individuals <10 kg were without any corpus luteum, and all individual >16 kg had 2 corpora lutea). This has to be taken into account when making management decisions. Indeed, particularly selective culling of yearlings in poor condition, i.e. with low body mass, and preserving of heavier individuals, can have a significant impact on fawn production, and hence also on the reproduction of roe deer in the following year(s).