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1

Roost selection by non-breeding Leisler's bats (Nyctalus leisleri) in montane woodlands: implications for habitat management

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Spada M., Szentkuti S., Zambelli N., Mattei-Roesli M., Moretti M., Bontadina F., Arlettaz R., Tosi G., Martinoli A.
Acta Chiropterologica
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2008
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tom 10
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nr 1
We investigated roost selection by Leisler's bat (Nyctalus leisleri) before and after hibernation in 2005 in a mountain area of southern Switzerland. The study area is dominated by deciduous trees and characterised by the presence of previously managed chestnut (Castanea sativa) orchards that are now partly abandoned. In March–May and August–October, 15 radio-tracked bats (seven males and eight females) used 28 roost trees. We analysed roosts used by N. leisleri at three different levels: (i) micro-scale: features of roost cavities; (ii) meso-scale: characteristics of selected roost trees and (iii) macro-scale: structure of woodland surrounding roost trees. Selection at meso and macro-scales was obtained comparing characteristics of roost trees and surrounding woodland with potentially available trees and woodlands. Bats roosted mainly in live chestnut trees, with large diameter and absence of vegetation near the entrance. Roost trees were located closer to streams, in woodlands with a higher percentage of sweet chestnut trees and a lower tree density than random trees. Multifunctional forest management in abandoned chestnut stands, comprising recreation (chestnut harvesting) and preservation of a semi-natural habitat and its related biodiversity, would recreate the traditional woodland features – in particular an open forest structure with low tree density and presence of ancient chestnut trees – and provide suitable roosting sites to migratory N. leisleri.
2

Describing roosts used by forest bats: the importance of microclimate

100%
Boyles J. G.
Acta Chiropterologica
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2007
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tom 09
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nr 1
Adequate descriptions of roosting habitat are vital to the management and conservation of bats. However, most studies on bat roosting preference report only structural characteristics of roosts and surrounding habitat, and ignore potentially important factors in roost selection. I argue that the current methods for describing the roosting habitat of tree-roosting bats can be improved, and that more emphasis should be placed on designing studies to determine why bats choose particular roosts. Herein, I focus on measuring microclimate in roosts because it universally influences habitat selection. Specifically, roost temperature is easily measured and is likely an important microclimate variable used by bats in roost selection. Variation in structural characteristics of roosts is often assumed to correlate with variation in microclimate of the roost; however, empirical data are too scarce to verify this assumption. I suggest improvements to the current methods of describing roost characteristics and suggest the inclusion of new methods to describe microclimate. In summation, I argue that there are methods of measuring roost characteristics that may be beneficial to use in conjunction with the methods currently being used, and that microclimate should be considered when designing future studies.
3

Bats select buildings in clearings in Bialowieza Primeval Forest

100%
Mazurska K., Ruczynski I.
Acta Chiropterologica
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2008
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tom 10
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nr 2
Species dominance structure and selection of buildings by bats were studied during the breeding season in areas surrounding the well-preserved stands of Białowieża Primeval Forest (BPF), potentially offering an abundance of tree cavities. Searches for bats were carried out during daylight hours and at evening emergence. Thirty eight of the 238 buildings surveyed from May to August, 2002 were used by 708 bats. Only three of the 12 resident species of bats occupied buildings, amongst these Vespertilio murinus and Eptesicus serotinus were the most common, found in 16 and 15 buildings, respectively. Pipistrellus pygmaeus was located in two buildings. This suggests that limited access to old-growth forests (potentially rich in tree cavities) may not be a crucial factor leading to the occupation of buildings by those species. Selection of buildings by bats was further investigated by comparing 14 characteristics of those buildings occupied by bats to those unused. Six of these characteristics were shown to have a significant influence. Using Akaike's Information Criterion (AICc), the most important categories for selection were roof lining and building size. This would suggest that the criterion for the selection of buildings by these species is based not only on its location but on these key structural attributes.
4

Divergent microclimates in artificial and natural roosts of the large-footed myotis (Myotis macropus)

80%
Campbell S., Coulson G., Lumsden L. F.
Acta Chiropterologica
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2010
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tom 12
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nr 1
The thermal environment of day roosts is considered one of the most influential factors affecting the survival, growth and reproduction of microbats. The use of torpor is a common energy saving strategy employed by microbats in temperate regions. The efficiency of entry into, and arousal from, torpor is governed by roost microclimate, primarily roost temperature. The large-footed myotis Myotis macropus roosts in both tree cavities and a man-made tunnel at Yan Yean reservoir in Victoria, Australia. We investigated the thermal properties of both roost types in comparison to available tree cavities and ambient temperature over four time periods from October 2003 to May 2005. Tree cavities and tunnel roosts remained significantly warmer at night, cooler during the day, and were more stable than ambient temperatures. In addition, roost tree cavities were significantly cooler between 10:00–13:00 h compared to available tree cavities, and there was a trend for roost tree cavities to be slightly warmer at night and slower to reach maximum temperature relative to available tree cavities during the breeding season (October–January). In contrast, there was little difference in roost and available tree cavity temperatures outside of the breeding season (April–May). Temperatures inside tunnel roosts were more stable and were significantly cooler during the afternoon compared to roost tree cavities during both the breeding and non-breeding seasons. Myotis macropus may actively trade-off the enhanced thermoregulatory benefits of warm roosts for reduced predation risk associated with the tunnel roosting environment.
5

Interannual fidelity to roosting habitat and flight paths by female western barbastelle bats

80%
Hillen J., Kiefer A., Veith M.
Acta Chiropterologica
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2010
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tom 12
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nr 1
The roost area selection of reproductive female western barbastelles was examined throughout four study seasons (2004–2007) via radio-tracking and automated acoustic monitoring. We specifically analysed the spatial structure of the roosting habitat and roost fidelity including a flight path connecting the roosts. We radio-tracked 13 colony members to 46 natural roosts, mainly dead oaks with large pieces of loose bark. Simultaneous tracking of four pairs of females revealed the existence of subgroups and fission-fusion-behaviour in Barbastella barbastellus. The colony displayed fidelity to the roost area rather than to single roost trees, although some trees were reused in two or three study seasons. Bimodal activity patterns obtained from acoustic monitoring indicated that the flight path connecting two core roosting areas functioned as a commuting corridor.
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