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The influence of altitude gradient on the animal communities in the Eastern Tatra Mountains of Slovakia has never been studied. There are some rare, endemic and relict animal species and even a group of small terrestrial mammals native to the Tatra Mountains. Between 2009 and 2014, research was conducted on the impact of altitude gradient on the species richness, abundance and composition of small mammal communities in the Eastern Tatras. In total, more than 16 species were trapped, including snow voles, tatra voles and alpine shrews, three species endemic to the Carpathian Mountains. The species richness of small mammals declined at higher elevations. The endemic alpine shrew was found at altitudes of 914 and 1007 m above sea level, while tatra voles were recorded almost along the entire gradient studied. Snow voles ranged only above the tree line at altitudes of 1574 to 1775 m, in the Rock slope habitat. On the other hand, generalists colonised various parts of the gradient at different altitudes, while specialists were bound to specific habitats whose presence was limited by altitude. The composition of small mammal communities evidently and significantly varied with rising elevation and with the biotope type in the area under observation. Our results suggest that the composition of the community reflects changes in environmental conditions and the biological limits of the particular small mammal species in the altitude gradient as well as the combination of neighbouring habitats and the resources they provide.

Food supply in the nesting territories of species has a key role to the species diet composition and their breeding success. Red-footed falcon (Falco vespertinus) preys predominantly on larger insect species with a supplementary portion of smaller vertebrates. In the breeding periods 2014 and 2016 their food supply, focusing on Orthoptera, Mantodea, Rodentia and Eulipotyphla, was analysed at five historical nesting sites of the species in Slovakia. Preference for these prey groups in the diet was also studied at the last active nesting site in this country. Overall we recorded 45 Orthoptera species (of which 23 species are known as the food of the red-footed falcon), one species of Mantodea, 10 species of Rodentia (of which 2 species are known as the food of the red-footed falcon) and 5 species of the Eulipotyphla order in the food supply. With regard to the availability of the falcons' preferred food, in both years the most suitable was the Tvrdošovce site, which continuously showed the greatest range and abundance of particular species. In the interannual comparison the insects showed lower variability in abundance than the small mammals. In 2014 the growth of the common vole (Microtus arvalis) population culminated and with the exception of a single site (Bodza) a slump in abundance was recorded in 2016. In comparing the diet composition with the food supply at the last Slovak breeding site Rusovce (Special Protection Area Sysľovské polia), we recorded significant preference for grasshopper Caliptamus italicus (in 2014), common vole (in 2016) and cricket Tettigonia viridissima (in both years) in the falcons' diet. They did not prey on the Apodemus sylvaticus species belonging among the abundant small mammal species in that locality. Conservation measures in the agricultural landscape are discussed in relation to homogeneous red-footed falcon breeding territories.

Somatic features (morphometric or meristic features, i.e., body weight, length of body, tail, hind foot and ear) and reproduction characteristics (number of embryos in uterus, reproduction potential, duration of reproduction season) are the basic attributes of the biology of a species. In the present paper, biometry of somatic characteristics and reproduction potential of two mountain vole species, the Tatra vole (Microtus tatricus) and the snow vole (Chionomys nivalis) which originate from various sites of Slovakia, were investigated. Among somatic features, the body length, tail length, hind foot length, length of ear and body weight were assessed. The highest variability was found in body length and the lowest one in the hind foot length. These characteristics were evaluated separately for sub-adult and adult individuals, and males and females. Values of somatic features and body weight of both species are larger in males than in females. Throughout the life of these rodents, the ratio between the length of tail and length of body does not vary considerably. The reproductive potential of the two species is, compared to other small mammals, very low and the length of reproductive season is shorter in the extreme conditions of the mountain environment. Thanks to a sufficient data set, it was possible to evaluate the influence of altitude on somatic features as well as on reproduction potential of M. tatricus and it was found that the average values of somatic features and body weight increased with increasing altitude.

Reintroductions are considered an important part of the action plans and recovery strategies of endangered ground squirrel species, but so far little is known about their proper methodology. We collected primary data on 12 European ground squirrel reintroduction projects carried out at 14 localities in the Czech Republic, Slovakia and Poland since 1989. We focused on seven methodological aspects of each reintroduction: selection of release site, method of releasing, date of releasing, origin of released animals, total number of released animals, mean number of released animals per season and reintroduction site management. The method of releasing was found to be the key factor in determining the settlement of animals at the target locality. Only soft releasing methods, i.e. the use of enclosures and/or artificial burrows, ensure that animals remain at the target locality. The other factors significantly determining reintroduction success are the number of released animals per season (at least 23 animals required) and the total number of released animals (a minimum of 60 individuals). Long-term management of the site and regular monitoring of the newly established population are necessary. Our recommendations, based on experience with the successes and failures of previous reintroductions, could largely improve the efficiency of future reintroductions of highly endangered species.

Habitat fragmentation may influence the genetic make-up and adaptability of endangered populations. To facilitate genetic monitoring of the endangered European ground squirrel (EGS), we analyzed 382 individuals from 16 populations in Central Europe, covering almost half of its natural range. We tested how fragmentation affects the genetic architecture of presumably selectively neutral (12 microsatellites) and non-neutral (the major histocompatibility class II DRB gene) loci. Spatial genetic analyses defined two groups of populations, “western” and “eastern”, with a significantly higher level of habitat fragmentation in the former group. The highly fragmented western populations had significantly lower genetic diversity in both types of markers. Only one allele of the DRB gene predominated in populations of the western group, while four alleles were evenly distributed across the eastern populations. Coefficient of inbreeding values (F IS) calculated from microsatellites were significantly higher in the western (0.27–0.79) than in eastern populations (−0.060–0.119). Inter-population differentiation was very high, but similar in both groups (western F ST = 0.23, eastern F ST = 0.25). The test of isolation by distance was significant for the whole dataset, as well as for the two groups analyzed separately. Comparison of genetic variability and structure on microsatellites and the DRB gene does not provide any evidence for contemporary selection on MHC genes. We suggest that genetic drift in small bottlenecked and fragmented populations may overact the role of balancing selection. Based on the resulting risk of inbreeding depression in the western populations, we support population management by crossbreeding between the western and eastern populations.

The morphometrics and reproduction of shrews (Sorex araneus, S. minutus, S. alpinus) was studied in Slovakia. Significant differences in weight, body length and tail length were recorded in adult and subadult shrews. Adult individuals and males had higher mean somatometric values (apart from tail length of subadults). The hind foot length was the least variable characteristic, which can be considered as the most stable taxonomic somatic characteristic of shrews. Weight and body length varied considerably. Values of somatic characteristics in S. araneus and S. minutus increased with increasing altitude, apart from hind foot length in S. araneus, which decreased with increasing altitude. The values of somatic characteristics declined with increasing continentality, but tail length gradually increased in the direction west — east at the highland level. Sorex minutus was characterized by the greatest reproductive activity (length of reproductive cycle April–October, average number of embryos 6.97). The lowest reproductive activity was observed in S. alpinus (average number of embryos 5.72). The mating season of S. araneus began at the end of March and ended in August with an average number of embryos of 6.12.