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

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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.
ENDANGERED SPECIES RESEARCH
Endang Species Res
Preprint, 2009
doi: 10.3354/esr00194 Published online April 28, 2009
INTRODUCTION
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 (www.iucnredlist.org) 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 · www.int-res.com*Corresponding author: Email: gareth.jones@bristol.ac.uk
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’
OPENPEN
ACCESSCCESS
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.
MATERIALS AND METHODS
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
species.
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
landscape’.
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
2
Knight & Jones: Importance of night roosts for bat conservation
the dominant habitat types around each roost could be
quantified.
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.
(2002).
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
locations.
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
3
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%.
RESULTS
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
20.3°C.
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
4
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
Juvenile
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
kilometers
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.
DISCUSSION
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-
6
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
Overall
(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
Overall
(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.
CONCLUSIONS AND PERSPECTIVES
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.
7
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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8
Editorial responsibility: Stephen Rossiter,
London, UK
Submitted: November 28, 2008; Accepted: March 5, 2009
Proofs received from author(s): April 22, 2009
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