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Importance of night roosts for bat conservation: Roosting behaviour of the lesser horseshoe bat Rhinolophus hipposideros



Safeguarding day roosts is of key importance in bat conservation. However, little emphasis has been placed on the conservation of night roosts, although these may act as refuges close to foraging grounds. We studied the roosting behaviour of the lesser horseshoe bat Rhinolophus hipposideros, a species that has declined over large areas of Europe, and radio-tracked 54 bats from 3 maternity roosts in contrasting landscapes in Britain. The bats exhibited multimodal patterns of overnight activity (mean ind. -1 : 2.1 to 4.5 night roosting bouts). More than 75% of bats used night roosts away from the maternity roost, typically in buildings. Up to 5 different night roosts were used by individual bats, with the number of night roosts correlated with home range and core area. Night roosts were significantly nearer to core foraging areas than were maternity roosts, with 64 to 86% contained within core nuclei. Multimodal activity patterns and frequent use of night roosts are impor- tant aspects of R. hipposideros behaviour that need to be considered in management strategies. We postulate that minimisation of distance to feeding sites may be the primary function of the night roosts, with roosts being used for resting and digestion between foraging bouts. Night roosts are therefore an integral part of core foraging areas and require protection.
Endang Species Res
Preprint, 2009
doi: 10.3354/esr00194 Published online April 28, 2009
Bats spend a large proportion of their lives roosting,
and insectivorous species have a wide diversity of
roosting habits (Kunz & Lumsden 2003). Many bats
form maternity roosts where large numbers of females
congregate to give birth and raise their young. These
roosts are arguably sites of prime conservation con-
cern. Disturbance and destruction of day roost sites is a
major factor in bat population declines (Kunz 1982),
and as such the protection of day roosts may be of
great importance in modern bat conservation efforts
(Fenton 1997). However, much less emphasis has been
placed on the use and conservation of roosts used dur-
ing the night (night roosts), and yet occupation of night
roosts between foraging flights is a common habit of
temperate insectivorous bats (Anthony et al. 1981, Bar-
clay 1982, Lewis 1994, Jaberg & Blant 2003).
To help define the needs of night roosting bats in a
rural setting we studied the roosting behaviour of the
lesser horseshoe bat Rhinolophus hipposideros. Al-
though this species is listed in the category of ‘Least
Concern’ globally in the latest IUCN Red List of Threat-
ened Species ( its numbers are de-
creasing; the species underwent a dramatic decline in
western Europe, where it is now regarded as endan-
gered in many areas (Stebbings 1988, Ohlendorf 1997).
In northern Europe R. hipposideros generally roosts in
buildings during the summer and uses caves and mines
during the hibernation period. Although the use of
night roosts by R. hipposideros has been reported pre-
viously (Gaisler 1963a, McAney & Fairley 1988), re-
search has focussed on maternity roosts and hiberna-
tion sites. For example, within Britain the general
characteristics of R. hipposideros maternity roosts have
been well documented (McAney & Fairley 1988), and
© Inter-Research 2009 ·*Corresponding author: Email:
Importance of night roosts for bat conservation:
roosting behaviour of the lesser horseshoe bat
Rhinolophus hipposideros
Tessa Knight, Gareth Jones*
School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
ABSTRACT: Safeguarding day roosts is of key importance in bat conservation. However, little
emphasis has been placed on the conservation of night roosts, although these may act as refuges
close to foraging grounds. We studied the roosting behaviour of the lesser horseshoe bat Rhinolophus
hipposideros, a species that has declined over large areas of Europe, and radio-tracked 54 bats from
3 maternity roosts in contrasting landscapes in Britain. The bats exhibited multimodal patterns of
overnight activity (mean ind.–1: 2.1 to 4.5 night roosting bouts). More than 75% of bats used night
roosts away from the maternity roost, typically in buildings. Up to 5 different night roosts were used
by individual bats, with the number of night roosts correlated with home range and core area. Night
roosts were significantly nearer to core foraging areas than were maternity roosts, with 64 to 86%
contained within core nuclei. Multimodal activity patterns and frequent use of night roosts are impor-
tant aspects of R. hipposideros behaviour that need to be considered in management strategies. We
postulate that minimisation of distance to feeding sites may be the primary function of the night
roosts, with roosts being used for resting and digestion between foraging bouts. Night roosts are
therefore an integral part of core foraging areas and require protection.
KEY WORDS: Rhinolophidae · Habitat management · Nocturnal activity · Multimodal
Resale or republication not permitted without written consent of the publisher
Contribution to the Theme Section ‘Bats: status, threats and conservation successes’
Endang Species Res: Preprint, 2009
ongoing monitoring of colony counts at maternity roosts
and hibernation sites is widespread (Warren & Witter
2002). However, much less is known about use of roosts
at night.
Early studies of overnight activity of the species
failed to describe any overall pattern (Gaisler 1963a,
McAney & Fairley 1988). However, more recent
exploratory work using radio-telemetry has indicated
multimodal phases of activity, with 2 to 4 foraging
bouts (Bontadina et al. 2002). This multimodal pattern
is unusual. A review by Erkert (1982) found that insec-
tivorous bats characteristically follow a bimodal pat-
tern of activity, whereby a peak in activity is recorded
following emergence from the roost at dusk, with a
second smaller peak at the end of the night before
dawn. During lactation female bats often return to
maternity roosts in the middle of the night to suckle
offspring (Swift 1980, Maier 1992). The pattern of over-
night activity in Rhinolophus hipposideros may sug-
gest that night roosting behaviour is of greater impor-
tance than previously believed and therefore warrants
more extensive study.
Kunz (1982) suggested 5 possible functions of night
roosts: energy conservation, digestion, predator avoid-
ance, information transfer and social interactions.
Roost switching to conserve energy may reflect the
selection of optimal microclimate, for example during
sub-optimal foraging conditions or to enable torpor, or
the minimisation of distance to feeding sites (Kunz &
Lumsden 2003, Lausen & Barclay 2003). We used
radio-telemetry to investigate the behaviour of Rhi-
nolophus hipposideros to test the following predic-
tions: (1) that night roosts are significantly nearer to
foraging grounds; (2) that the species exhibits multi-
modal patterns of activity through the night; and (3)
that temporal variation in overnight patterns relates to
weather conditions. We discuss the importance of
night roosts as refuges in close proximity to key forag-
ing sites and suggest that this has significant implica-
tions for the conservation value of such roosts. Our
results will directly aid the development of manage-
ment plans and may also be more widely applicable to
other bat species in rural and semi-rural landscapes.
Study sites and land use mapping. The study was
conducted during early to late May (defined as early
pregnancy), late May to early June (late pregnancy),
late July to mid-August (lactation) and late August to
mid-September (post-lactation) in 2003 to 2005. We
radio-tracked bats from 3 maternity roosts in contrast-
ing landscape types. The ‘lowland landscape’ roost
was a colony of ~160 animals (including juveniles) lo-
cated in the attic space of a converted barn in Upper
Langford, North Somerset, England (51° 19’ N, 2° 46’W,
~40 m above sea level [a.s.l.]). The surrounding land-
scape is predominantly lowland pastoral farmland
(about 30% of land cover within 2 km of the roost),
with <10% arable, and an extensive wooded scarp to
the southeast (about 23% woodland cover, including
about 5% broad-leaved woodland within 2 km). The
colony was typical of many found in lowland areas in
southwest England and south Wales.
The second maternity colony studied was in what we
considered a ‘high quality’ landscape situated in the
Wye Valley. The roost was a maternity colony of ~750
bats within a small barn in Brockweir, Gloucestershire,
England (51° 43’ N, 2° 40’ W, ~120 m a.s.l.). The Wye
Valley and Forest of Dean (Wales/England border)
support 26% of the British population of Rhinolophus
hipposideros. This area is designated a Special Area of
Conservation (SAC; EU code UK0014794) and com-
prises 26.2% broad-leaved deciduous woodland,
which is considerably higher than the national average
(5.8% in England, 6.1 % in Wales). Broad-leaved
woodland is a key foraging habitat for R. hipposideros
(Bontadina et al. 2002). Other important habitats
within 2 km of the roost included >40% pastureland
and the River Wye. On the basis of the nature of the
surrounding habitat and the large roost size, we classi-
fied this landscape a priori as ‘high quality’ for the
Our third study site was a colony of ~130 animals
within a large barn in Llanbedr, Brecon Beacons
National Park, Wales (51°53’ N, 3°06’ W, ~247 m a.s.l.).
The roost was in a valley characterised by numerous
small streams, pasture farmland and sizeable areas of
forestry plantation. Above the valley the landscape
was dominated by open moorland. Indeed, about 50%
of the habitat within 2 km of the roost site was moor-
land dominated by bracken or heath vegetation. The
presence of large areas of moorland and coniferous
non-native forestry plantation (about 15%) in the area,
and the relatively high altitude of this site led us to
consider it a priori as being of relatively low quality for
the species. We refer to this landscape as the ‘upland
We undertook Phase 1 habitat surveys (JNCC 1993)
of the study sites and mapped all areas of settlement,
defined as built-up areas with associated gardens and
infrastructure, which included roads, individual scat-
tered properties and villages/towns. Base maps (Ord-
nance Survey Land-Line.Plus, multi-scale) were
obtained from Digimap (© Crown Copyright Ordnance
Survey, EDINA Digimap/JISC) and converted for use
in the GIS software ArcView GIS 3.2 (ESRI GIS and
Mapping Software) with Map Manager (ESRI). Land-
use maps were then generated with ArcView so that
Knight & Jones: Importance of night roosts for bat conservation
the dominant habitat types around each roost could be
Radio-telemetry. We caught bats in a static hand net
as they emerged from the roost, except for 18 ind.
which we caught in the roost. Bats were assigned a
reproductive class, defined as juvenile (yearlings with
grey fur and lacking ossification of the epiphyseal
joints in the finger bones [Anthony 1988]), nulliparous
(females lacking pelvic nipples) (Gaisler 1963b) or
adult (parous females with pelvic nipples). Forearm
length was recorded to 0.1 mm, using callipers and
bats were weighed to 0.1 g in a small plastic bag using
a Pesola (Baar) Micro-Line 30 g scale. Between 2 and 6
bats were selected per session for radio tagging.
Emphasis was placed on studying female bats, and any
males caught were disregarded unless juvenile. Larger
bats were selected to minimise risk of adverse effects
of carrying extra weight, using forearm length as a
measure of skeletal size, following Bontadina et al.
The fur between the scapulae was clipped and a
radio transmitter (<0.35 g PIP3, Biotrack) attached
using Skinbond (Smith and Nephew, supplied by
Alana Ecology). Tagged bats were ringed (banded)
using 2.9 mm magnesium-aluminium flanged rings
(Mammal Society). The transmitters increased the
body mass of adult females by mean 6.2% (range 4.9 to
8.1%), of nulliparous females by mean 7.1% (range 6.5
to 8.8%) and of juveniles by mean 7.2 % (range 6.7 to
7.8%). The increased body mass recorded in adult
females is comparable with the 4.5 to 8.1% increase
documented by Bontadina et al. (2002) in their study
on Rhinolophus hipposideros in which they concluded
that the transmitters had no demonstrable adverse
effect on flight behaviour.
We located bats using a Lotek Suretrack STR_1000
receiver (Lotek Wireless) connected to either a hand-
held directional 3-element Yagi aerial or a magnetic
whip aerial on the car roof. Locations were recorded at
5 min intervals on a Garmin GPSmap76 Global Posi-
tioning System (minimum accuracy ± 10 m) using the
‘homing-in’ method (Kenward 2001). Homing-in has
been used successfully to radio-track flying greater
horseshoe bats Rhinolophus ferrumequinum (Duvergé
& Jones 2003, Flanders & Jones 2009). Lesser horse-
shoe bats fly more slowly than greater horseshoe bats
and we are confident that homing-in was an appropri-
ate method to use in this study. On the small number of
occasions when access to sites was restricted, we took
bearings using a prismatic compass, and distance to
the bat was estimated from the minimum signal
strength, knowledge of the terrain and observer expe-
rience (O’Donnell 2000). Each location (hereafter
termed a fix) was recorded on maps with an estimated
accuracy of ±100 m. If we felt there was poor resolution
of a fix (signal faint, i.e. high gain or direction uncer-
tain, e.g. due to signal bounce) then we omitted the fix
from the analysis. Although bats were followed contin-
uously, analysis was undertaken using fixes recorded
at 15 min intervals to minimise autocorrelation (Harris
et al. 1990).
An activity category was assigned for each fix: com-
muting (rapid, directional movements between distant
sites), foraging (sustained activity within a defined
area of variable size), perching (typically a period of
inactivity <10 min where the bat was hanging from a
tree), night roosting (typically a period of inactivity
>10 min within a building) or day roosting (see Russo
et al. 2002).
Weather conditions were recorded at dusk and dawn
and at hourly intervals in between: air temperature
(°C), wind speed (Beaufort scale) and rainfall (ranked
descriptively as 0 = none, 1 = spots, 2 = drizzle, 3 = fine,
4 = moderate, 5 = heavy, 6 = torrential).
Data analysis. We used Ranges 7 v1.0 (South & Ken-
ward 2006) (Anatrack) to calculate seasonal home
ranges as 100% minimum convex polygons (MCPs)
(Mohr 1947) of all fixes. We then used cluster analysis
(Kenward 2001) to remove outlying fixes and describe
core areas (Harris et al. 1990). We created 85 % cluster
cores (i.e. based on 85% of fixes) using only commut-
ing, foraging and perching fixes, hereafter termed as
‘active core’ areas. As commuting fixes are generally
removed by the use of cluster cores, the active cores
typically represent core foraging areas, comprising
one or more distinct nuclei. This therefore allows com-
parison between core foraging areas and night roost
Correlations between different response variables
were tested using the non-parametric Spearman’s
rank-order correlation (Dytham 1999). General linear
modelling (GLM) was used to analyse the radio-track-
ing data. The following response variables were
tested: mean number of night roosts used, mean num-
ber of night roosting bouts per night, mean length of
average night roosting bout and minimum distance
between the night roosts and nearest nuclei. The mean
nightly value of the first 4 response variables over the
number of nights that each bat was tracked was used
to avoid pseudoreplication. Explanatory categorical
variables were reproductive status and landscape type
(i.e. locality) and, where appropriate, minimum night
temperature, average nightly rainfall and average
nightly wind speed (continuous variables). The model
simplification process using the GLM approach as
advocated by Grafen & Hails (2002) was employed to
reduce multiplicity of p-values. The assumptions of the
GLM (independence, homogeneity of variance, nor-
mality of error and linearity/additivity) were tested
using histograms of residuals, normal probability plots
Endang Species Res: Preprint, 2009
and plots of standardised residuals against the fitted
values/continuous variables, and transformations
(square root and natural log) were used where re-
quired. Multiple comparisons among the means of sig-
nificant categorical explanatory variables were under-
taken using Tukey’s method.
Statistical analyses were carried out on Minitab ver-
sion 13.32 for Windows (Minitab) with a significance
level of 5%.
Data were obtained from 54 Rhinolophus hippo-
sideros radio-tracked in May to September during
2003 to 2005 (Table 1). The mean (± SD) number of
nights with full data was 2.7 ± 1.2, 2.8 ± 1.0 and 2.7 ±
0.9 in the lowland, high quality and upland land-
scapes, respectively. Sampling effort was similar for
each reproductive class and landscape. Two-way
ANOVA with replication showed that the mean num-
ber of fixes per bat did not vary significantly among
reproductive classes (F3,36 = 2.75, not significant [ns])
and landscape (F2,36 = 1.85, ns) whilst ANOVA showed
that between localities, bats were radio-tracked on
similar dates (using Julian days) (F2,142 = 0.119, ns). The
range of minimum night temperatures was 4.3 to
The majority of bats were recorded night roosting in
one or more locations away from the maternity roost.
Night roosting activity was restricted to the maternity
roost in only 19% of the bats sampled (lowland: n = 6,
high quality: n = 2, upland: n = 2). These were adult
females during late pregnancy and lactation, and juve-
niles, although use of alternative night roosts was
recorded in each group. We identified a total of 55
night roost sites, although the exact structure of 7
roosts could not be determined due to lack of access.
The remaining roosts were predominantly within a
variety of man-made structures: outbuildings associ-
ated with domestic properties (n = 15), old barns (n =
10), garages (n = 9), stables (n = 2), a porch (n = 1), and
derelict buildings (n = 3). Seven barns were 2-storey,
whereas other buildings were typically single-storey.
Roof structure was varied and included flat felt roofs
(on garages and outbuildings) and sloping or pitched
tiled/slate/corrugated iron roofs. A feature of all of the
buildings was their open-aspect, with an often sizeable
opening ranging from an open window/doorway to
open front. A further 6 roosts were in underground
structures: caves (n = 2), cellars (n = 2), former railway
tunnel (n = 1), former lime kiln (n = 1). Roosting in trees
was seldom recorded (n = 2) and was believed to be
opportunistic, as use was not repeated. Of the roosts
occurring within the ‘settlement’ habitat type (built-up
areas with associated gardens and infrastructures),
93%, 57 % and 75 % were in the lowland, high quality
and upland landscapes respectively (Fig. 1). The mean
(± SD) distance of the night roosts from the maternity
roost was 1.71 ± 0.98 km (range 0.03 to 3.44 km, n = 29)
in the lowland landscape, 2.40 ± 1.44 km (range 0.32 to
3.50 km, n = 14) in the high quality landscape and
1.34 ± 0.86 km (range 0.82 to 3.05 km, n = 12) in the
upland landscape.
The maximum number of different night roosts
recorded being used by any bat was 5, with a mean of
1.3 ± 0.9, 1.6 ± 1.6 and 1.8 ± 1.2 different night roosts
(excluding the maternity roost) per bat in the lowland,
high quality and upland landscapes, respectively. The
number of night roosts (square-root transformed) did
not vary among landscapes (F2,46 = 0.89, ns) or accord-
ing to reproductive status (F5,46 = 0.32, ns). There was
a positive correlation between the number of night
roosts used (excluding and including the maternity
No. of individuals tracked Mean total no. of fixes per bat (± 1 SD)
Lowland High quality Upland Lowland High quality Upland
Adult female
Early pregnancy 6 36.2 ± 8.6
Late pregnancy 6 3 3 57.7 ± 28.5 54.0 ± 32.1 59.3 ± 28.5
Lactation 6 3 3 57.0 ± 29.7 63.7 ± 13.7 66.0 ± 33.7
Post-lactation 6 3 3 43.0 ± 24.7 73.0 ± 2.0 100.7 ± 23.2
Nulliparous female 6 59.8 ± 25.9
Female 2 99.0 ± 7.1
Male 4 101.0 ± 16.7
Totals 36 9 9 59.0 ± 29.8 63.6 ± 19.3 75.3 ± 31.5
Overall total 54 62.5 ± 28.8
Table 1. Rhinolophus hipposideros. Sampling effort for radio-tracked individuals during summers of 2003–2005 in 3 different
landscape types in Britain. See ‘Materials and methods’ for details of ‘lowland’, ‘high quality’ and ‘upland’. Blanks indicate
no data available
Knight & Jones: Importance of night roosts for bat conservation 5
Fig. 1. Rhinolophus hipposideros. Distribution of maternity colonies (d) and night roosts (d) in relation to settlement habitat type
(light grey lines and areas) in the (a) lowland, (b) high quality and (c) upland landscapes in southern Britain. Colony home range
is delimited by a 100% minimum convex polygon (thick line) of fixes from all bats radio-tracked from the maternity roost during
2003 to 2005. The distribution of the active core nuclei (small areas bounded by thin lines) is also shown. In all cases the maternity
sites also functioned as night roosts
Endang Species Res: Preprint, 2009
roost) and the home range (100% MCP) (rS= 0.40, p <
0.01; rS= 0.42, p < 0.01, respectively). There was also a
positive correlation between the number of night
roosts used (excluding and including the maternity
roost) and the total size of the active cores (rS= 0.32, p <
0.05; rS= 0.41, p < 0.01, respectively).
The distribution of the night roosts in the 3 landscape
types in relation to the active core nuclei (Fig. 1) shows
that, overall, night roosts were contained predomi-
nantly within the active cores of all bats. On only 2
occasions did bats use night roosts (outside core areas)
as transit roosts between the maternity roost and dis-
tant core foraging areas. In both instances the roosts
were used when heavy rain curtailed commuting
activity. Three night roosts within the lowland land-
scape were situated between 2 different foraging areas
and could therefore have been acting as transit roosts.
All other night roosts were either contained within, or
were adjacent to the core foraging area(s). Individu-
ally, 86, 64 and 67% of night roosts were contained
within active cores within the lowland, high quality
and upland landscape, respectively. The distances of
the nearest active core nuclei from night roosts are
provided in Table 2. The minimum distance between
the night roosts and nearest nuclei did not vary among
landscapes (F2,36 = 0.53, ns) and was not affected by
reproductive status (F5,36 = 0.93, ns). The minimum dis-
tance of the active core nuclei from night roosts is sig-
nificantly smaller than the minimum distance of the
active core nuclei from the maternity roost (Wilcoxon
signed-rank test = 572.50, p < 0.05).
The bats showed multimodal phases of activity dur-
ing the night. There were between 1 and 8 night-roost-
ing bouts (mean range 2.1 to 4.5, depending on land-
scape and reproductive status). Night-roosting bouts
lasted on average 76 to 81 min (Table 3). In general,
bats emerged from the night roost before dawn for the
final flying bout, except for 9% of cases in which they
remained in the night roost through to dawn. The num-
ber of night roosting bouts did not vary among land-
scapes (F2,45 = 2.10, ns) but was affected by reproduc-
tive status (F5,45 = 2.46, p < 0.05). Multiple comparisons
for status indicated that the number of night roosting
bouts was significantly shorter in early and late preg-
nancy compared with post-lactation, probably a reflec-
tion of varying night length. Average wind speed sig-
nificantly affected number of bouts (F1,45 = 7.71, p <
0.01), with stronger winds associated with more bouts.
Minimum temperature, average rainfall and all interac-
tion terms were removed during model simplification.
Length of the average night roosting bout (log-trans-
formed) did not vary among landscapes (F2,43 = 0.48,
ns) and was not affected by reproductive status (F5,43 =
1.75, ns) or minimum air temperature (F1,43 = 3.82, p =
0.057). It was affected by rainfall (inverse-transformed)
(F1,43 = 9.69, p < 0.01) and wind speed (F1,43 = 9.79, p <
0.01), with shorter night roosting bouts associated with
increased rainfall and stronger winds. Interaction
terms were removed during model simplification.
Night roosts were typically found within core home
range areas, supporting the hypothesis that roost
switching during the night allows minimisation of dis-
tance to feeding sites. Feeding habitat has been shown
to be important for selection of maternity roosts in
buildings, for example in Plecotus auritus (Entwistle et
al. 1997), Pipistrellus sp. (Oakeley & Jones 1998), and
Rhinolophus hipposideros (Reiter 2004). Therefore it is
likely that feeding habitat may also be important for
selection of night roosts. Conversely, however, we sug-
Distance of night roost from
nearest nucleus (m)
Lowland High quality Upland
Adult female
Early pregnancy 42 ± 65.2
Late pregnancy 254 ± 308.4 13 ± 23.1 173 ± 193.3
Lactation 81 ± 83.7 50 ± 0.0 190 ± 94.3
Post-lactation 119 ± 199.4 91 ± 116.7 3 ± 5.8
Nulliparous female 28 ± 28.4
Juvenile 15 ± 26.0
(adults only) 115 ± 179.7 52 ± 78.9 105 ± 129.8
Table 2. Rhinolophus hipposideros. Distance of edge of
nearest nuclei in active core areas from night roosts for
radio-tracked individuals in 3 different landscapes in Britain
during 2003 to 2005. Values are means ± 1 SD; blanks
indicate no data available
Average night roosting bout (min)
Lowland High quality Upland
Adult female
Early pregnancy 100 ± 34.9
Late pregnancy 69 ± 33.6 107 ± 52.7 107 ± 102.2
Lactation 84 ± 56.6 58 ± 23.4 47 ± 9.6
Post-lactation 71 ± 30.9 64 ± 30.0 73 ± 31.4
Nulliparous female 102 ± 69.4
Juvenile 85 ± 53.3
(adults only) 81 ± 39.6 76 ± 40.0 76 ± 59.7
Table 3. Rhinolophus hipposideros. Length of average night
roosting bout (min) recorded for radio-tracked individuals
from maternity roosts in 3 different landscapes in Britain
during 2003 to 2005. Values are means ± 1 SD; blanks indicate
no data available
Knight & Jones: Importance of night roosts for bat conservation
gest that given the proximity of night roosts to the core
areas, feeding habitat may equally be constrained by
availability of night roosts. The number of night roosts
was significantly correlated with home range parame-
ters (home range and core area). Therefore it can be
postulated that a reduction in availability of night
roosts could result in a corresponding reduction in
home range. Availability of suitable maternity roosts
may represent a primary constraint on the population
size and distribution of different bat species (Humph-
rey 1975); further work is required to determine if this
is also the case for night roosts.
The bats showed multimodal phases of activity
throughout the reproductive season, with significantly
more bouts occurring during post-lactation. Several
hypotheses have been used to explain night roosting in
bats, including thermoregulation (Anthony et al. 1981),
information exchange (Wilkinson 1992), a reduction in
prey availability (Anthony et al. 1981) and digestion
(Barclay 1982). Anthony et al. (1981) observed that
night roosting decreased with increasing temperature
and postulated that night roosts are used for ther-
moregulation. However, we found that sub-optimal
foraging conditions of stronger winds and increased
rainfall reflected reduced time spent night roosting.
Therefore it seems unlikely that night roosts serve pri-
marily in a thermoregulatory capacity for Rhinolophus
hipposideros. As regards the second hypothesis, since
internal checks on night roosts were avoided in the
study to avoid disturbance and disruption of activity
patterns, it is not possible to comment on the potential
social function of these roosts. However, roosts are
likely to be communal, as they were used by more than
1 ind. from the same colony during successive tracking
sessions. When exploring kin-biased behaviour in R.
ferrumequinum, Rossiter et al. (2002) found that fe-
male bats and their adult daughters often shared night
roosts, sometimes over several years, and no cases
were recorded of non-relatives using the same night
roost. Night roosts may therefore be important centres
for information transfer among relatives, and this
should be considered in conservation.
Reduction of prey availability explains unimodal or bi-
modal behaviour, as peaks of activity coincide with
overnight peaks in insect numbers at dusk and, to a
lesser extent, dawn (Taylor 1963). Rhinolophus hip-
posideros take mostly crepuscular Diptera by aerial
hawking (Vaughan 1997, Knight 2006) and many of the
families of Nematocera found in the diet of R. hip-
posideros together with Trichoptera and Sphaeroceridae
are known to exhibit swarming behaviour. However
moths, which are active all night with a peak activity oc-
curring around midnight (Rydell et al. 1996), and non-
volant prey are also present in the diet. The broad diet
of the species may therefore allow it to feed throughout
the night, for example feeding predominantly on swarm-
ing insects at dusk and dawn, and mainly on moths and
non-volant prey during the intervening period, hence
resulting in multimodal activity patterns.
Given periodic feeding throughout the night and the
presence of faecal pellets within night roosts, it is likely
that night roosts are used for digestion of food. We have
shown that night roosts are in close proximity to the
core foraging areas, and their use allows minimisation
of distance to feeding sites. We suggest that minimisation
of distance to feeding sites may be the primary function
of the night roosts, which are used for resting and diges-
tion between foraging bouts, with a secondary use for
communal behaviour. As such, we postulate that night
roosts are integral to the core foraging areas.
This study has highlighted the importance of rural
settlements for Rhinolophus hipposideros. However,
the fact that night roosts are typically in buildings may
lead to conflict. Many of the barns and outbuildings
utilised are of period construction and the potential for
conversion to dwellings is high. However, bats often
fail to return to traditional roosts in barns after conver-
sion for residential use, even if mitigation is in place
(Briggs 2004). The multimodal nature of activity and
frequent use of night roosts and alternative day roosts
is a significant aspect of R. hipposideros behaviour,
and should be considered carefully by conservation
planners when designing management strategies to
conserve the species. Although bat roosts are pro-
tected by law (e.g. the EC Habitats Directive 1992),
current attention has largely focussed on day roosts.
We have shown that night roosts are integral to core
foraging areas and believe their protection is required
to help maintain bat populations near human settle-
ments. The usefulness of night roosts to lesser horse-
shoe bats will depend critically on their availability
close to important foraging sites. Studies on potential
availability of night roosts will therefore be valuable.
Given that many of the sites used especially old
barns and outbuildings are often renovated and
made inaccessible to bats, we expect that the limited
availability of night roosts may influence the selection
of foraging patches in some cases. Ultimately, an
experimental approach that removes access to some
night roosts and explores consequences may be
revealing, though this approach may be inappropriate
if there are likely detrimental consequences for the
bats. We recommend that the protection of night roosts
should also be given a high priority until further
research has been undertaken into the potential impli-
cations of their loss.
Endang Species Res: Preprint, 2009
Acknowledgements. We thank the following for their assis-
tance in the field: S. Rawles, G. Hitchcock, M. Robertson, J.
Knight, E. Ford, T. Vernelli, M. Zeale, S. Johnson, R. Guillem,
C. Rogers, C. Stone, J. Winfield and G. Winters. We are grate-
ful to the householders who provided access to roosts and the
landowners who granted access onto their land during the
radio-tracking. This work was carried out under licence from
Natural England and Countryside Council for Wales. T.K. was
funded by Countryside Council for Wales, Forestry Commis-
sion, Mammals Trust UK and Natural England. We are espe-
cially grateful to C. Bowen, N. Al-Fulaij, L. Halliwell, J.
Matthews, B. Mayle, T. Mitchell-Jones and K. Watts for their
input at project meetings. F. Bontadina and 2 anonymous ref-
erees provided valuable comments on an earlier draft.
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Editorial responsibility: Stephen Rossiter,
London, UK
Submitted: November 28, 2008; Accepted: March 5, 2009
Proofs received from author(s): April 22, 2009
... Frequency of night roosting depends on multiple factors, including reproductive status and time of year ( Anthony et al., 1981;Barclay, 1982;Ormsbee et al., 2007). Understanding functions of night roosts in anthropogenic structures can benefit conservation efforts toward declining bat species (Ormsbee et al., 2007;Knight and Jones, 2009). ...
... To our knowledge this study is the first description of night-roosting behaviors for the northern long-eared myotis, as rigorous studies on night roosting are inherently difficult with these nocturnal volant organisms (Ormsbee et al., 2007). Night roosts often are described as staging areas dominated by long periods (.1 h) of inactivity, some with clustering individuals (Barclay, 1982;Kunz, 1982;Ormsbee et al., 2007;Knight and Jones, 2009). Our data for the northern long-eared myotis showed that generally solitary individuals (88.3%) were active and alert (heads up) at night roosts, with most behavioral events of short duration (10 min). ...
... Limitations of the surrounding natural environment might have contributed to the frequent use of this bridge as a night roost. Such structures might need to be considered in conservation strategies for declining bat species (see Ormsbee et al., 2007;Knight and Jones, 2009). ...
The northern long-eared myotis (Myotis septentrionalis) occurs across much of eastern North America and is listed as federally threatened in the United States due to pervasive population declines. Limited data are available about roosting behaviors for this imperiled species. We report on night-roosting behaviors for the northern long-eared myotis under a bridge in northwestern Nebraska. Grooming, short visits, and feeding were the most frequently observed behaviors. Grooming, inactivity, and nursing had the longest durations, albeit all averaged <15 min per event. We also documented movement and urination infrequently. Prey manipulation associated with feeding was a frequent behavior and consisted of individuals facing upward or downward, culling wings, elytra, and legs of large prey items. When facing upward wing and tail membranes formed a cup against the abutment wall that likely limited loss of prey. Individuals used the bridge throughout the night but roosted most frequently at 4 and 8 h after sunset (00:15 and 04:15 h, respectively), with early morning activity dominated by feeding/prey manipulation. Our study showed night roosts were used frequently for many reasons, especially for grooming and consumption of large prey. Our observations represent the first description of night-roosting behaviors for the northern long-eared myotis.
... Some cave-dwelling species compensate the absence of suitable caves by synanthropic behaviour and use buildings as roosts (e.g., Kunz 1982;Voigt et al. 2016). This roosting strategy may reduce commuting distance (Knight and Jones 2009), and may allow bats to explore new habitats (Fenton et al. 2002;Mazurska and Ruczyński 2008), as well as to extend their geographical range (Fenton 1970;Kunz and Reynolds 2003). The identification and characterization of these roost alternatives is thus essential in order to integrate buildings into conservation measures and is the central focus of the present study. ...
... Night roosts of both species differed from day roosts by giving less protection against light, predators, and weather, which was also reflected in higher daily temperature fluctuations. The function of this roost type, namely resting and digesting between foraging bouts (e.g., Shiel et al. 1999;Ormsbee et al. 2007) with a minimized distance to foraging sites (Knight and Jones 2009;Downs et al. 2016), may explain why less protected roosts were accepted at night. The fact that we did not observe night roosts shared between the two species may thus be accounted for by reduced structural and microclimatic requirements leading to a large choice of suitable buildings used during a part of the night only. ...
Full-text available
Synanthropic roosting may allow cave-dwelling bats to cope with habitat fragmentation provided that suitable buildings are sustainably protected. This study on Asinara Island, Sardinia, focuses on roost requirements in synanthropy at different life stages of two endangered bat species, Rhinolophus hipposideros and Rhinolophus ferrumequinum. We rated the roost potential of 532 buildings and compared it with actual roost usage. Microclimate was compared across different roost types and between species, and bat composition and behaviour in nurseries of R. hipposideros were related to roost structure and microclimate. The two species occupied 25% of structures rated as “high potential”, versus 5% and 0% rated as “intermediate” and “low potential”. Concerning microclimate, R. hipposideros preferred warmer and drier day roosts, with higher temperature fluctuations during summer, while winter, and night, roost microclimate was comparable between species. In larger, warmer, and drier nurseries, colony size and proportion of reproductive females were higher and parturition started earlier. Before parturition, roost temperatures were inversely correlated to clustering, supporting its thermoregulatory function. Mothers spent in total 50% of the night inside the nursery caring the pup. Roost microclimate, size, and location close to foraging areas may thus promote breeding success. We conclude that a structure-based rating of roost potential supplemented by species-specific microclimatic requirements constitutes a promising predictor of roost usage. Moreover, adequate buildings support the complete life cycle of R. hipposideros in the absence of suitable caves. Buildings thus deserve increased protection measures in fragmented Mediterranean landscapes to ensure sustainable bat conservation.
... The use of colony surroundings by horseshoe bats was investigated by both direct observation (McAney, Fairley, 1988;Schofield, 1996;Motte, Libois, 2002) and telemetry (Bontadina et al., 2002;Motte, Libois, 2002;Zahn et al., 2008, Knight, Gareth, 2009. Most authors emphasize the essence of linear elements of the landscape as factors important for the protection of the colonies. ...
... In late summer and early autumn, the lesser horseshoe bat forages more intensively than in the rest of seasons. This hypothesis was confirmed by Knight and Gareth (2009) in telemetry research, where seasonal changes in the feeding area were also observed. Similar results were reported for other species: Pipistrellus pipistrellus and Myotis daubentonii (Kapfer, Serge, 2007), and Nyctalus leisleri (Shiel, Fairley, 1999). ...
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Lesser horseshoes are bats quite strongly attached to their roost sites and are considered as sedentary species avoiding long-distance migration. In Poland, the range of occurrence of the lesser horseshoe bat is restricted to mountain areas, where they prefer overgrown mountain streams for their feeding grounds. Due to these features, even seemingly small habitat changes are likely to have serious implications for maintaining local subpopulations of this rare and endangered species. In Radziechowy village, where trees were cut in the Wiesnik stream (bat feeding area), a change in the use of feeding grounds by lesser horseshoe bats was observed. This publication additionally describes the time and the manner of departure of bats from their roost. The study was conducted before the logging (2012) and immediately after the logging (2013–2016), near a church, from the most beneficial point. The study was conducted by a team of 2-3 members, starting each time 15 minutes before sunset and finishing after the bats departure. Lesser horseshoe bats avoid light and open space and they leave their roost in a complicated way. It is established that there is a statistically significant correlation (r = 0.992, p< 0.001) between sunset and emergence time of bats from the roost site. In this paper, during the emergence time, the weather influence was observed. On a cloudy day, an earlier emergence time was observed — 9 minutes after the sunset, while the average emergence time for all observations was 23.3 minutes. The conducted detector watches proved that bats most likely use the closest environment of the colony within a radius of 150–200 meters. Lesser horseshoe bats were observed in ditches of roadside trees, dense hedges and backyard orchards overgrown with apples and pears, which is typical for this species.
... Because bats often use a given roost for several weeks or months and may reutilise it over years, slow poisoning of synanthropic bats in the roost, where they might not die immediately but suffer sublethal effects over time, is possible ( Voigt et al., 2016). The probability of exposure to pesticides may be more pronounced when bats use night-roosts to pause from nocturnal activity, in case pesticides are spread in the evening, because in such cases bats may roost in exposed outbuildings such as woodsheds or porches (Knight and Jones, 2009) or even hang from trees ( ). ...
... Because bats often use a given roost for several weeks or months and may reutilise it over years, slow poisoning of synanthropic bats in the roost, where they might not die immediately but suffer sublethal effects over time, is possible ( Voigt et al., 2016). The risk may be more pronounced when bats use night-roosts to pause from nocturnal activity, in case pesticides are spread in the evening, because in such cases bats may roost in exposed outbuildings such as woodsheds or porches (Knight and Jones, 2009) or even hang from trees ( ). ...
Full-text available
Abstract Bats are an important group of mammals, frequently foraging in farmland and potentially exposed to pesticides. This statement considers whether the current risk assessment performed for birds and ground dwelling mammals exposed to pesticides is also protective of bats. Three main issues were addressed. Firstly, whether bats are toxicologically more or less sensitive than the most sensitive birds and mammals. Secondly, whether oral exposure of bats to pesticides is greater or lower than in ground dwelling mammals and birds. Thirdly, whether there are other important exposure routes relevant to bats. A large variation in toxicological sensitivity and no relationship between sensitivity of bats and bird or mammal test‐species to pesticides could be found. In addition, bats have unique traits, such as echolocation and torpor which can be adversely affected by exposure to pesticides and which are not covered by the endpoints currently selected for wild mammal risk assessment. The current exposure assessment methodology was used for oral exposure and adapted to bats using bat‐specific parameters. For oral exposure, it was concluded that for most standard risk assessment scenarios the current approach did not cover exposure of bats to pesticide residues in food. Calculations of potential dermal exposure for bats foraging during spraying operations suggest that this may be a very important exposure route. Dermal routes of exposure should be combined with inhalation and oral exposure. Based on the evidence compiled, the Panel concludes that bats are not adequately covered by the current risk assessment approach, and that there is a need to develop a bat‐specific risk assessment scheme. In general, there was scarcity of data to assess the risks for bat exposed to pesticides. Recommendations for research are made, including identification of alternatives to laboratory testing of bats to assess toxicological effects.
... First, a bat roost must be warm and safe (Michaelse 2014), and there should be food in the vicinity (Knight and Jones 2009). For gleaners such as long-eared bats, which are able to feed on insects that live inside the roost, e.g. in churches or barns (Rydell 1989;Kervyn et al. 2012), it is also important that the roost is large enough to permit indoor flight and harbor food in meaningful amounts. ...
Light pollution, light in the wrong place at the wrong time, is an emerging environmental issue with wide-ranging consequences. It interferes with the fundamental 24 h light–dark cycle, and has biological effects at all levels, from molecules to ecosystems, including human health and welfare. Here, exemplified by flood-lit churches, artificial lights compromise the survival of resident bats, as darkness provides protection from predation. We predicted that brown long-eared bats Plecotus auritus emerging from churches should (1) avoid illuminated church walls, and (2) avoid extended flights in the open. To test these predictions, bats were observed emerging from 33 country churches in Sweden. A model for light intensity at increasing distances from light sources was made. This model, in combination with known distance between church walls and surrounding lamps, was used to predict lux levels (lx) at each church wall. Higher light intensities were strictly avoided and the majority of bats emerged when light intensities at church walls were below 1.25 lx. Further, most brown long-eared bats flew into the canopy of trees less than 15 m distant from the churches. Bats and their roosts are strictly protected in Europe, but this is poorly enforced with respect to churches and other historical buildings. Nevertheless, lighting of buildings is a key issue in bat conservation and of worldwide significance. We strongly advise that installation of lights near historical buildings is regulated and subject to environmental impact assessments.
... The variations in the number of bat visits across the nighttime suggest that bats take rest in between their foraging bouts in night roosts, which fastens digestion processes (e.g. Knight and Jones 2009;Geluso et al. 2018). ...
Many plant species have seeds embedded in their fleshy pulp to attract frugivores, which enhances the chance of seed dispersal. However, some tropical plants are evolved with sharp spines to avoid herbivores and/or to prevent water loss, which makes foraging by frugivores difficult. Such plants receive frugivores’ attention, either because of resource scarcity or adaptive behavioural plasticity. We have a limited understanding of how fruit-eating animals access fruits protected by spines. In this 1-year study, we describe bat foraging on a spiny tropical shrub, Ziziphus mauritiana (Rhamnaceae) whose dried branches are often used by the local people to capture bats in caves that inevitably damage their wing membranes. The greater short-nosed fruit bat, Cynopterus sphinx was the only visitor to this spiny plant during its fruiting season and predominantly extracted fruits using a hovering tactic (on 81% observations) without damaging wing membranes. The hovering enabled them to extract fruits quicker than when alighting on the tree. Bats carried all the fruits away from the parent tree to feeding roosts for consumption. Bat foraging has thus effectuated short-distance seed dispersal (range 11–70 m radii) in which most seeds (30.73%) were found at the distance of 31–40 m in our search up to 150 m. Although bats extracted both ripe and unripe fruits, ripe-fruit extraction was 4.5 × higher than the unripe fruits. This study shows the tradeoff between getting a good meal and contending with spines in a resource-scarce habitat. Besides, this study describes the adaptive foraging tactics of greater short-nosed fruit bats that facilitate short-distance seed dispersal.
... Buildings are critical roosting resources for bats (Voigt et al., 2016) and may have greater significance for bats at higher elevations and latitudes where roosts with optimal temperatures may be less available (Johnson et al., 2019). Building roosts satisfy a host of roosting requirements for different ages, sexes, and species and should be conserved, especially as other roosts become scarcer or experience greater disturbance (Knight & Jones, 2009;Kunz & Reynolds, 2003;Voigt et al., 2016). ...
Full-text available
Abstract White‐nose syndrome (WNS) has caused the death of millions of bats, but the impacts have been more difficult to identify in western North America. Understanding how WNS, or other threats, impacts western bats may require monitoring other roosts, such as maternity roosts and night roosts, where bats aggregate in large numbers. Little brown bats (Myotis lucifugus) are experiencing some of the greatest declines from WNS. Estimating survival and understanding population dynamics can provide valuable data for assessing population declines and informing conservation efforts. We conducted a 5‐year mark–recapture study of two M. lucifugus roosts in Colorado. We used the robust design model to estimate apparent survival, fidelity, and abundance to understand population dynamics, and environmental covariates to understand how summer and winter weather conditions impact adult female survival. We compared the fidelity and capture probability of M. lucifugus between colonies to understand how bats use such roosts. Overwinter survival increased with the number of days with temperatures below freezing (β > 0.100, SE = 0.003) and decreased with the number of days with snow cover (β
... The reproductive number (R0) for SARS-CoV-2 is considered high with suggestions that in a naïve human population an average of two to four new infections may be generated from a single infectious human ). The average incubation period is estimated to be between two and 14 days, with a median of four days, and it is not known to what extent shedding of the virus may occur within this period prior to the onset of clinical signs (Guan et al. 2020;Mizumoto et al. 2020;Yee et al. 2020 Given that animal to animal transmission has been shown for Rousettus aegyptiacus bats, as well for felids, canids, rodents and mustelids (Chan et al. 2020;Freuling et al. 2020;Shi et al. 2020), and that bats often roost in large numbers, which may aid in facilitating disease dissemination within populations (Knight & Jones, 2009;Lau et al. 2010), there is a medium probability of dissemination of SARS-CoV-2 among bat populations in England. ...
The newly evolved coronavirus, SARS‐CoV‐2, which has precipitated a global Covid‐19 pandemic among the human population, has been shown to be associated with disease in captive wild animals. Bats (Chiroptera) have been shown to be susceptible to experimental infection and therefore may be at risk from disease when in contact with infected people. Numerous conservation fieldwork activities are undertaken across the United Kingdom bringing potentially infected people into close proximity with bats. In this study we analysed the risks of disease from SARS‐CoV‐2 to free‐living bat species in England through fieldworkers undertaking conservation activities and ecological survey work, using a qualitative, transparent method devised for assessing threats of disease to free‐living wild animals. The probability of exposure of bats to SARS‐CoV‐2 through fieldwork activities was estimated to range from negligible to high, depending on the proximity between bats and people during the activity. The likelihood of infection after exposure was estimated to be high and the probability of dissemination of the virus through bat populations medium. The likelihood of clinical disease occurring in infected bats was low and therefore the ecological, economic and environmental consequences predicted to be low. The overall risk estimation was low and therefore mitigation measures are advisable. There is uncertainty in the pathogenicity of SARS‐CoV‐2 in bats and therefore in the risk estimation. Disease risk management measures are suggested, including the use of personal protective equipment, good hand hygiene and following the existing government advice. The disease risk analysis should be updated as information on the epidemiology of SARS‐CoV‐2 and related viruses in bats improves. The re‐analysis may be informed by health surveillance of free‐living bats.
... During the random selection of buildings in our study, it is likely that a greater number of buildings in urban areas were selected than buildings in rural areas simply because a large proportion of the study area comprised conurbations. R. hipposideros is known to be sensitive to urban development (Jung and Threlfall 2016), meaning that our building pseudo-absences model predicted that any area outside of conurbations was a suitable habitat for a maternity roost, which did not aid us in narrowing down priority areas to search for new roosts. Our study demonstrates the importance of exploring the influence of different pseudo-absence selections on species distribution models. ...
Full-text available
In the UK, four out of 18 bat species are listed on the EU Habitats Directive, including the lesser horseshoe bat (Rhinolophus hipposideros), and their population status is closely monitored by visiting known roosts. R. hipposideros predominantly form maternity roosts in buildings, but roosts are impermanent features in the landscape and their distribution changes as bats form new roosts and abandon others. Locating new roosts requires intensive surveys which are challenging and inefficient. In this study, we provide a novel model-based strategy to identify potential R. hipposideros maternity roost sites that can be used to monitor bat populations. First, we model potential maternity roost habitat using record centre data on roost locations across Wales, Great Britain. We then constrain the area identified from modelling using record centre data on locations of bats in areas with no known roosts. We used two variable selection methods and three pseudo-absence data sets (random background points, random points in buildings and target group selection of mammal records) to produce six habitat suitability models. The three pseudo-absence data sets produced different habitat suitability maps, demonstrating the influence of pseudo-absence selection on species distribution models. The six models were combined using weighted mean average to produce an ensemble model that performed better than individual models and that indicated high levels of congruence in areas predicted to have high habitat suitability for maternity roosts. Our model revealed an extensive area (6523 km²; 31% of the area of Wales) containing 18,051 buildings in suitable habitat. Using record centre data on bat activity outside commuting range from known roosts reduced the potential survey area to 133 km² (0.6% of the area of Wales) and 207 buildings. Our modelling outputs can be used to direct volunteers and bat surveyors in more targeted and efficient searches.
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Although the ultimate causes of high bat fatalities at wind farms are not well understood, several lines of evidence suggest that bats are attracted to wind turbines. One hypothesis is that bats would be attracted to turbines as a foraging resource if the insects that bats prey upon are commonly present on and around the turbine towers. To investigate the role that foraging activity may play in bat fatalities, we conducted a series of surveys at a wind farm in the southern Great Plains of the US from 2011–2016. From acoustic monitoring we recorded foraging activity, including feeding buzzes indicative of prey capture, in the immediate vicinity of turbine towers from all six bat species known to be present at this site. From insect surveys we found Lepidoptera, Coleoptera, and Orthoptera in consistently high proportions over several years suggesting that food resources for bats were consistently available at wind turbines. We used DNA barcoding techniques to assess bat diet composition of (1) stomach contents from 47 eastern red bat ( Lasiurus borealis ) and 24 hoary bat ( Lasiurus cinereus ) carcasses collected in fatality searches, and (2) fecal pellets from 23 eastern red bats that were found on turbine towers, transformers, and tower doors. We found that the majority of the eastern red bat and hoary bat stomachs, the two bat species most commonly found in fatality searches at this site, were full or partially full, indicating that the bats were likely killed while foraging. Although Lepidoptera and Orthoptera dominated the diets of these two bat species, both consumed a range of prey items with individual bats having from one to six insect species in their stomachs at the time of death. The prey items identified from eastern red bat fecal pellets showed similar results. A comparison of the turbine insect community to the diet analysis results revealed that the most abundant insects at wind turbines, including terrestrial insects such as crickets and several important crop pests, were also commonly eaten by eastern red and hoary bats. Collectively, these findings suggest that bats are actively foraging around wind turbines and that measures to minimize bat fatalities should be broadly implemented at wind facilities.
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The flight activity of three species of insectivorous bats and their prey was studied in north-east Scotland (57 degrees N) during summer 1993. Aerial insects of sizes taken by bats were more abundant during the day than during the night, but the highest abundance usually occurred around dusk, partly reflecting increased flight of dipterans. In contrast, the flight activity of moths, mainly Geometridae and Pyralidae, was greatest around midnight. Two species of aerial-hawking bats, Pipistrellus pipistrellus and Myotis daubentonii, which feed primarily on small flying insects, mainly Diptera, emerged from their roosts 15-30 min after sunset, during or after the dusk peak in insect activity, and subsequently foraged as their food was declining in abundance. In contrast, the foliage gleaning bat Plecotus auritus, which feeds primarily on moths, did not emerge until about one hour after sunset, but while the activity of its main prey was increasing. The two aerial-hawking bats therefore seem to be constrained from exploiting most of the evening peak in aerial insect abundance, presumably because earlier emergence would result in higher predation risk at the higher light levels. P. auritus may have less to gain by emerging early, since it can feed on moths and non-flying prey independently of the activity of small insects at dusk. The conclusions have implications for the conservation of bats and their habitats particularly at high latitudes. Protective tree cover may allow earlier evening emergence of bats and therefore provide access to more food.
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1. One of the key threats to bats in Britain is loss of suitable roost sites, but little is known about roost requirements for most species. 2. Roost selection in the brown long-eared bat Plecotus auritus was demonstrated by comparison of buildings used as summer roosts in north-east Scotland with (i) random buildings in the same area, and (ii) a set of adjacent houses located in the same habitat. 3. Buildings containing roosts were situated closer to woodland and water relative to the random houses, and also had a greater area of woodland within a radius of 0.5 km, but not at distances beyond this. This suggests that feeding habitat in the vicinity of the roost is important for roost selection. 4. When compared with adjacent houses, roosts were older, and had roof spaces divided into more compartments, which were more likely to be fully lined with rough wooden planking. 5. The temperatures inside summer roosts (mean 17.9°C) were significantly warmer than those from random and adjacent houses (mean 16.7°C). 6. These results suggest that P. auritus is selective of its roosts, relative to the houses available. 7. The selection of specific types of roosts by P. auritus has implications for the management advice provided when roosts are threatened, and conservation actions should focus on efforts to avert significant change to, or destruction of, roost sites or the woodland in their vicinity.
Terrestrial organisms live in an environment that, by its geophysical nature, is subject to profound rhythmic alteration. The rotation of the earth brings about a 24-hr periodicity in light intensity, temperature, and humidity. As the earth revolves around the sun there are annual changes in day length, temperature, and the duration of twilight, which become more pronounced at increasing latitudes; that is, over the period of a year the form, level, and amplitude of diurnal variables themselves vary to different degrees. Other effects result from the revolution of the moon about the earth. The rhythmic gravitational fluctuations so produced are of little relevance to terrestrial animals, but there are also variations in night-time brightness with lunar periodicity. Organisms have adapted to this temporal structure of their environment in different ways. Very early in evolution they developed endogenous diurnal rhythms with periods of approximately 24 hr. These circadian rhythms were coupled with the external diurnal cycle by special synchronizing mechanisms so that a certain relatively stable phase relation, characteristic of each species, was maintained. In many cases circalunar and circannual endogenous rhythms evolved in addition to the circadian rhythm; these, too, are synchronized with the corresponding environmental variables by special mechanisms.
Population structure of the threatened long-tailed bat (Chalinolobus tuberculatus) was studied over five summers between 1993 and 1998. in temperate Nothofagus rainforest in Fiordland, New Zealand. Composition of 95 communal groups was sampled and spatial distribution of individually marked bats investigated. Individual C. tuberculatus moved to new roost sites virtually every day. Long term non-random associations among individuals were found by a cluster analysis that revealed three distinct social groups. Groups contained on average 72.0 (± 26.0) (mean ± SD), 99.3 (± 19.0) and 131.7 (± 16.5) marked individuals/year. Collective foraging ranges of the three groups overlapped but roosting occurred in three geographically distinct adjacent areas. Only 1.6% of individuals switched between groups. Non-reproductive females and males switched between groups more often than reproductive females but individuals switched only once or twice during the study and then just for one night. Juveniles of both sexes were associated with their natal group as 1 year-olds and then later when breeding. Social groups were cryptic because foraging ranges of groups overlapped, bats belonging to each group spread over many roosts each day, and these roost sites changed from day to day. Bats moved infrequently between groups, potentially linking the local population assemblages. Future research should explore whether the population is structured in denies. Population structure did not conform to traditional metapopulation models because groups occurred in homogeneous habitat extending over a large geographical area. Conserving bat populations should entail preserving a representative number of subgroups but development of models for predicting minimum number of effective local populations is still required.
We quantified the percentage cover of habitats and the extent of linear features within 2 km of 11 maternity roosts of the 55 kHz phonic type of pipistelles Pipistrellus pipistrellus in south-west England, and compared these with habitats around random points. The dominant habitats around both roosts and random points were improved grassland and built-up areas. There was significantly more water (especially water edge habitat with woodland or hedgerow on the banks), and continuous hedgerow with emergent trees, around roosts. Preference for freshwater habitats around roosts was shown in comparisons of single habitats, and in compositional analyses with and without the inclusion of urbanized random points. These habitats may be preferred by 55 kHz pipistrelles: riparian habitats support large numbers of flying insects of the types eaten by 55 kHz pipistrelles, and hedgerows may be important linear features used by bats. The conservation of continuous hedgerows and watercourses close to maternity roosts would appear to be very important for 55 kHz pipistrelles.