Ábrahám Levente: Biomonitoring a Dráva folyó magyarországi szakasza mentén 2000-2004 - Natura Somogyiensis 7. (Kaposvár, 2005)

Dombi, Imre: Bat monitoring along the Drava River (Mammalia: Chiroptera) - Denevér-monitoring a Dráva mentén (Mammalia: Chiroptera)

DOMBI I.: BAT MONITORING ALONG THE DRAVA VALLEY 153 in the near surroundings. Restorations of buildings and lack of knowledge can cause its decrease in number. Its hunting areas can be found around the settlements. It is present in all four sampling areas along the Drava. Its traces and colonies of few individuals were found in all checked buildings. Significant colonies are known from Surd, Somogyudvarhely, Bolhó, the largest of them is of 25-30 individuals. Serotine bat {Eptesicus serotinus) It is common and wide-spread in the whole country, it occurs in settlements and in their close surroundings. Restorations of buildings and lack of knowledge can cause its decrease in number. Its hunting areas can be found around the settlements. It is present in all four sampling areas along the Drava. Its traces or colonies of few individuals were found in almost all the checked buildings. But only one significant colony was found in Zákányfalu that consists of 40-80 individuals. Barbastelle bat {Barbastella barbastellus) Endangered, rare species. It has already disappeared from most part of Europe, so the national stock should be treated with particular care (BIHARI 1996). Its most powerful stock is in the mid-mountains, but is also has data from the plains. There it finds its demands in old hardwood grove forests, sometimes in castle-parks, so that their disappearance or fragmentation leads to the extinction of the species. Along the Drava in all sampling areas its presence and also reproduction was proved. In Vízvár one lactating female turned up only in 2005, beforehand we did not know about the species! Results of different sampling methods The number of captured and tagged bats between 2000 - July 2005 is shown in Table 3. except for the small species {Pipistrellus sp., Myotis mystacinus and Myotis brandti) all the individuals of all the species were ringed. Several years' of recaptures have proved how much the long-eared bat {Plecotus auritus), the grey long-eared bat {Plecotus austriacus), the Barbastelle bat {Barbastella barbastellus) and the Bechstein's bat {Myotis bechsteini) depend and insist on their territories and habitats. The capture data do not reliably reflect the ratio of the stocks of different species. The low number of captures in case of the otherwise very common noctule bat (Nyctalus noctula), common pipistrelle (Pipistrellus pipistrellus) and soprano pipistrelle bat {Pipistrellus pygmeus) can be explained with their life-style and the circumstances of the captures. Those bats hunting high in the forests are captured rather rarely during a net capture method in the paths and openings. In case of the other species the ratios are approximately realistic, which are also backed up by the data gained through the batdetector observations. A great advantage of bat-detector observations is the greater number of individuals spotted and that we receive data on the relative frequency of those species hard to capture with net. Its disadvantage is the problems with identifying species. Sometimes individuals are only possible to be identified to genus level, but it happens that even that is hard to tell for sure. As an example Table 4. shows the results of the 2004 bat-detector observations. The great proportion of noctule bat {Nyctalus noctula) is clearly noticeable showing the real frequency of the species. The great number of detection of the three Pipistrellus sp., and the serotine bat {Eptesicus serotinus) is also apparent. These species can actually be considered as quite common, and they can be indicated more easily from a greater