Roost selection by barbastelle bats (Barbastella barbastellus, Chiroptera: Vespertilionidae) in beech woodlands of central Italy: consequences for conservation

Abstract

We investigated roost selection by Barbastella barbastellus in a mountainous area of central Italy. Twenty-five bats, mostly lactating females, were radio-tracked to 33 roost trees. Trees in unmanaged woodland were favoured as roost trees; woodland subject to limited logging was used in proportion to availability, and areas where open woodland and pasture occurred were avoided. Selection depended on tree condition (dead beech trees were preferred) and height (roost trees were taller than random ones). Cavity selection was based on cavity type, height and entrance direction: roost cavities were mainly beneath loose bark, at a greater height above ground and facing south more frequently than random cavities. Untouched areas of mature woodland should be preserved to provide roosting conditions for B. barbastellus. In logged areas, harvesting protocols should save dead and mature trees; frequent roost switching and small colony size imply that large numbers of roost trees are needed.

Introduction

Roosts play a crucial role in bat biology (e.g. Kunz, 1982), and their availability affects both the geographic occurrence of bat species and the diversity of bat communities (e.g. Findley, 1993). Many of the nearly 850 microchiropteran species roost in trees (e.g. Kunz, 1982, Brigham et al., 1997, Sedgeley & O'Donnell, 1999a, Boonman, 2000, Lakci & Schwierjohann, 2001, Menzel et al., 2002). Deforestation is regarded as a specially serious threat to conservation of these mammals (Hutson et al., 2001). Because old and dead trees are richer in cavities suitable for roosting, they may be particularly important for bats (Hutson et al., 2001, Parsons et al., 2003). The roosting requirements of tree-dwelling bat species represent a major conservation issue, and investigation of roost selection is needed to set up appropriate guidelines for forest management.

The barbastelle bat (Barbastella barbastellus (Schreber, 1774)) is a medium-sized vespertilionid (forearm length=36.5–43.5 mm, body mass=6–13.5 g.; Schober and Grimmberger, 1997) occurring in Europe, North Africa and Asia (Hutson et al., 2001, Urbanczyk, 1999). It is recorded over much of Europe, except in the highest latitudes (Iceland, Northern Ireland, Estonia and most of Scandinavia; Urbańczyk, 1999). B. barbastellus is classified as ‘Vulnerable’ at a global scale (Hutson et al., 2001), ‘Endangered’ in Italy (Bulgarini et al., 1998) and is threatened in many areas of Europe, especially in the west where it may be one of the rarest bat species (Urbańczyk, 1999). The species is protected by European law under Annexes II and IV of the Habitats Directive 92/43/EEC.

B. barbastellus shows roosting preferences that should be regarded as a key point in conservation protocols (Hutson et al., 2001). The species has been described as roosting mainly in human-made structures in summer, with trees being regarded as of secondary importance (Harrington et al., 1995, Schober & Grimmberger, 1997). However, radio-tracking studies have recently shown that B. barbastellus largely selects tree cavities as roosts (Greenaway, 2001, Steinhauser et al., 2002).

Few studies have dealt with roosting preferences in B. barbastellus: Greenaway (2001) examined roosting behaviour and activity of the species in Britain, while observations in continental Europe are limited to Germany (Steinhauser et al., 2002). Nothing is known about roost selection of B. barbastellus in southern Europe.

We examined roost selection in a breeding population of B. barbastellus from central Italy at three levels: woodland structure and management type; tree characteristics; and cavity characteristics. Our aim was to contribute to drawing up guidelines for conservation of this sensitive bat species in southern Europe.