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The cave Veternica, near the capital Zagreb, has been open for tourists since the 1960s, but bat friendly management started to develop in 2003 as a result of co-operation between the Nature Park Medvednica and the Croatian Biospeleo-logical Society. Restriction of tourist visits during bat hibernation was introduced in 2003 and a bat-friendly gate was built in 2006, with annual bat monitoring started in 2007. In the cave 18 bat species have been recorded until now. The cave is an important hibernation site for 8 bat species: Myotis bythii, M. daubentonii, M. emarginatus, M. myotis, M. nattereri, Rhinolophus hipposideros, R. euryale and R. ferrumequinum and an important summer roost for R. euryale and Miniopterus schreibersii. Winter monitoring is performed every year and includes two counts in January and February. The numbers of Lesser Horseshoe Bats in winter increased from 6 individuals in 1996 to 437 in 2013, and the trend shows significant exponential growth. This is probably related both to the restriction of touristic visits in the winter time and changes in cave gating from solid doors to horizontal bars. There are also reports from Czech Republic and Slovenia on growth in numbers of Lesser Horseshoe Bats with similar trends in some caves. Therefore we suspect that this increase in lesser horseshoe bat numbers may be a consequence of bat- friendly cave mana-gement and possibly reflect the bats‟ social learning.

Veternica Cave located in the vicinity of the Croatian capitol Zagreb is managed by the Nature Park Medvednica. The cave is open for tourists. In order to minimize bat disturbance Nature Park ordered 2-year research from the Croatian Biospeleological Society that was conducted from the end of 2003. till mid 2005. In the Veternica Cave 17 bat species have been recorded by now. Recent researches confirmed the presence of 13 bat species while during this project 12 bat species have been recorded. The cave is important hibernation site for 8 bat species: Myotis blythii, M. daubentonii, M. emarginatus, M. myotis, M. nattereri, Rhinolophus hipposideros, Rh. euryale and Rh. ferrumequinum that is in accordance with previous research. Occasionally, the cave is used by 4 more bat species during hibernation: Barbastella barbastellus, Eptesicus serotinus, Plecotus macrobullaris and M. bechsteinii. The cave is an important summer roost for 2 bats species: Miniopterus schreibersii and Rh. euryale. For the roost protection special bat friendly doors were constructed after project was finished. The maximum number of Rh. ferrumequinum decreased approximately 40% in the last 10 years. In this research we found only solitary individuals of Rh. euryale, which counted 130 individuals 10 years ago. The number of hibernating Rh. hipposideros bats increased 4 times. Compared to research undertaken 50 years ago the number of bats in the Min. schreibersii summer roost increased several times, while the numbers of bats in Rh. euryale bat summer roost stayed the same. A short-term influence of visitors on the cave temperature has been recorded. Nature Park Medvednica can use description of bat ecology, main characteristics used for bat determination, wing design of different species, photo and video material in educational/promotional purposes and for bat monitoring. This is the first cave in Croatia officially closed for visits during bat hibernation.

One of the biggest nurseries of the Longfingered Bat in Europe inhabits Miljacka II Cave in the Krka National Park, Croatia. The number of bats estimated by tally counters and on photo images counts about 6000 individuals. The bats use the cave from May till the end of October. Although other 6 more bat species use the cave during the same period of time the interspecies spatial distribution is not overlapping. Pregnant Longfingered bat females group in the cave in late April/early May while during late May/early June they deliver their young. The lactation continues till mid/end of July. The droppings of bats were collected every 15 days from May till October 2000 from beneath the colony applying special netted stool. Overall 309 bat droppings were analyzed. The seasonal differences in diet composition as well as diet differences during pregnancy/lactation were established using frequency analysis. The overall diet consisted mainly of aquatic insects belonging to Trichoptera and Chironomidae. The exception is October during which prevail Chironomidae and Lepidoptera. In the prey are also recorded some Aranae that bats may have collected from the water surfaces or spider nets while commuting to the nearby river. Other Insects recorded in the diet were Ephemeroptera, Odonata (Zygoptera), Plecoptera, Orthoptera (Ensifera – Tetigonidae), Coleoptera (Chrysomelidae, Anthicidae), Diptera (Nematocera – Tipulidae, Mycetophilidae, Cecidomydae, Limoniidae, Simulidae, Culicidae, Sciaridae), Brachycera, Hymenoptera (Symphita – Ichneumonidae, Braconidae, Chalcididae, Formicidae) and Homoptera (Aphididae, Psyllidae, Cercopidae).

Miniopterus schreibersii and Rhinolophus euryale are considered as priority species for autecological studies according to UNEP/Eurobats. In Croatia all bat species are legally protected. In the Croatian Red List (2004) M. schreibersii is in the EN category and R. euryale in the VU category. Research on both species started in 2003 in the Veternica Cave near the town of Zagreb, the capital of Croatia. The nursery of both species with ca 500 individuals uses the unprotected, warmest part of the cave. Although the cave is under the authority of Medvednica Nature Park, the bats are often disturbed since it is very close to the capital and guided tour is encouraged. The path leading to one of the popular tourist spots passes by the cave and bats may easily be disturbed. A data logger measuring the temperature and relative humidity every 5 minutes is located in the part used by bats. The bats usually start to use the cave in June and depending on the weather they may stay there until late October. In the year 2003 no young were recorded in the cave, but there were young in the following year. Possible reasons for this may include extensive disturbance by visitors. In this work we present data on current status of both species in Croatia, microclimate measurements, wing design of traced individuals and a proposal for using grills that would restrict disturbance of bats by visitors for the protection of that part of the cave.

The Veternica Cave is open for visitors and run by the Medvednica Nature Park. It is located near Zagreb, the capital of Croatia, and is one of the key bat spots for the northwestern part of Croatia. The total length of the cave passages is nearly 7, 000 m with very different microclimate conditions. The first 400 m are accessible for tourists and are under the influence of external climate. There have been 14 bat species recorded until now. Rhinolophus ferrumequinum and Rh. euryale form winter colonies and Rh. euryale and Miniopterus schreibersii use the cave as summer roost. Myotis daubentonii, M. nattereri, M. emarginatus, M. myotis, M. blythii and Rh. hipposideros are found in crevices or on cave walls throughout the winter mainly as solitary individuals in colder parts of the cave. During very cold weather the cave provides a valuable shelter for M. bechsteinii, Eptesicus serotinus, Barbastella barbastellus and Plecotus spp. In the winter of 2004, Plecotus macrobullaris was recorded in the cave and that part of Croatia in general, for the first time. Data loggers measuring temperature and humidity at 5 minute intervals are set at 5 sites on the cave walls. Temperature, humidity and wind speed were measured near individual bats. Data on microclimate preferences of different bat species are discussed and compared with data from research conducted in winter of 1995/1996. A significant decrease in the number of R. ferrumequinum and R. euryale has been noted and recommendations for bat conservation through sustainable cave management are offered.