working today for nature tomorrow - Justus-Liebig-Universität Gießen

(Nagel 1982, Leitl 1995). If bats are forced to come into contact with their faeces andparasites they tend to change roost site (Stratmann 1978, Wolz 1986).Experience with large bat boxes and their suitability as hibernation sites is limited. InGermany there are some observations with the noctule (Schwarting 1994b, Dieterich 1998,Wissing 1996b) and a single one with three specimens of Leisler’s bat (Meschede & Heller2000). Some noctules have been found dead in such boxes indicating that the walls were toothin to prevent the animals from being frozen.Exposure of bat boxesThere are some indications that the percentage of boxes occupied by bats grows with thenumber of boxes available to these animals. Schmidt (1990) raised the number of bat boxesin a eastern German pine forest continuously over some years. He observed a growingnumber of bat records until an abundance of about five bat boxes per 10 hectare was reachedat sunny and semi-shaded sites. It is proposed to put up at least 10-20 bat boxes in one placeto give bats the opportunity to use the most convenient ones and change roosts from time totime (Heidecke 1989, Heise 1983a, Henze 1963, Roer 1971, Schmidt 1977). Accumulationsof about three boxes each are not necessary in general, but may support social behaviour insome species, for example the noctule (Oldenburg & Hackethal 1989, Schmidt 1977). Ifboxes are used which are suitable for both bats and birds, one should hang them up in groupsas the territoriality of a breeding bird couple will chase other birds away, so some boxes willbe kept free for bats (Haensel & Näfe 1982, Henze 1963, Roer 1971). Such groups of bat orbird boxes should be put in place at intervals of 50-100 metres (Heidecke 1989, Schwarting1994a, Dieterich & Dieterich 1997b, Schmidt 1998).Proposals for where to distribute bat boxes are very diverse. In woodlands some authorsprefer places near forest roads, paths or forest edges, others put boxes right into the foreststands. It is proved that each particular place for a bat box may influence the probability ofcolonisation by a certain bat species (Leitl 1995).In Germany, bat boxes that were actually used by bats were at heights of between 1.5 metresand 6 metres (Meschede & Heller 2000). The noctule seems to prefer boxes more than 4metres above the ground due to its style of flight departure characterized by jumpingdownwards to get some speed first (Stratmann 1978, Kronwitter 1988a, Heise & Blohm1998).In practice the height of bat boxes should be dependent on the specific place. In generalboxes should be easily available for maintenance, at least with a portable ladder. The mostconvenient and effective heights are 2.5 to 4 metres. However, along forest roads and publicfootpaths it could be safer and the disturbance risk to bats lower if boxes are fixed higher inthe trees (Meschede & Heller 2000).The direction of exposure of bat boxes is of minor relevance. For years it has beenrecommended to put them up in south- or east-facing directions and so most recent bat boxeshave such exposures. Most important to the animals is the temperature inside the boxes,which is dependent on the exposure to sunshine. Bat boxes exposed to the north get shadowfrom the tree’s trunk for most of the time. Therefore in general bats prefer boxes directed tothe southwest, boxes to the south have moderate attraction and those directed to the northeastare of little interest to bats (Fuhrmann 1992). In spring and autumn bats prefer to roost in54