Ábrahám Levente (szerk.): Válogatott tanulmányok IX. - Natura Somogyiensis 24. (Kaposvár, 2014)
Szűcs D. - Kitti Horváth K. - Horváth Gy. F.: Comparing small mammal faunas based on barn owl (Tyto alba) pellets collected in two different lowland landscapes
Szűcs, D., Horváth, K. & Horváth, Gy. F.: Small mammal faunas 317 al. (2008) compared the abundance of small mammals of two geographically separated lowland areas (Drava Plain, Hevesi plane). This result showed that the species composition of small mammal assemblages did not differ significantly, but the frequency values of species and taxa categories as well the as temporal changes differed and shifted which related to structural changes and the usage of landscapes. In this study we also examined two lowland geographical regions, but in this case we investigated three hypotheses based on the relationship of small mammal abundance on three spatial scales. According to the distribution of abundance, the first hypothesis was incorrect in the case of two Sorex species on a mesoregional scale, because their relative frequency was inhomogeneous between the two investigated landscapes. This result was caused by different landscape structures, because there are many marshland areas preferred by this shrew species in the Győr basin. In a previous study we demonstrated that the proportion of the two genera of shrews (Sorex, Crocidura) was significantly higher in the Drava Lowlands than in the Heves plain, but when the population of common voles collapsed, the owls altered their food selection in accordance with prey availability in both studied regions. In that study year, the relative frequency of shrews was higher in the Heves plain than in the Drava Lowlands (Horváth et al. 2008). The two shrew genera (Sorex, Crocidura) which occurred with high abundance in the food composition of the bam owl showed different distribution patterns in the comparison of the Drava Lowland with the Győr basin. Sorex species were dominant in the Győr basin, in contrast the presence of Crocidura genus was higher in the Drava Lowland. Based on data of collected pellets form the Győr basin, the Lesser white-toothed shrew occurred with higher relative frequency in that region than the bicoloured white-toothed shrew, as presented in former pellet analyses (Andrési & Sodor 1987a,b). Our results disproved the assumption of Schmidt (1976) claiming that the bicoloured white-toothed shrew is dominant against the other shrew species in Western Hungary. The results of this study confirmed that the refinement of the spatial scale provided more detail in the differences of frequency distributions, and gave a more accurate picture on distribution and frequency relations. We highlighted three species whose values of relative frequency differed significantly between two landscapes on the microre- gional scale. Andrési & Sódor (1987a,b) showed the presence of two postglacial relict voles (root vole and field vole) as an important faunistical result, occurring in the food composition of the bam owl with low abundance, mainly in wet and sedgy habitats. Owl pellet samples from the 1980’s reported the presence of root vole in the area of Fertő Hanság. Based on data from pellets of the long-eared owl (Asio otus) and the short-eared owl (Asio flammeus) collected from two areas of Győr-Moson-Sopron county, a total of 20 root voles were found. In our study we detected only 5 specimens of field vole but root voles occurred with higher abundance (45 specimens). This result suggests that the field vole is rarer than the root vole in the area of the Fertő-Hanság, although the marshland areas of these landscapes mean potential habitats for the field vole. In contrast, based on pellet analysis and live trapping, this species is more common in the Kis- Balaton Landscape Protection Area whose composition and landscape structure is much similar to the Fertő-Hanság area (Schmidt 1967, Horváth et al. 2004a, b). Results from the previous studies of owl pellets, it is known that 30-40 years ago the striped field mouse did not occur in pellets collected from areas of mesoregions located in the northern and north-western partsd of Lake Balaton. However, its presence was shown in the area of the Fertő-Hanság in 2008, which is an important faunistic data, because this species is able to spread expansively. During the investigated four-year period, the frequency distribution and the extent of locations based on collected pellets from the Győr basin confirmed the stable north-western expansion of this species.
