Hystrix It. J. Mamm. (n.s.) 22(1) 2011: 159-166 Pag. 158 disegno THE WINTER DIET OF THE LESSER HORSESHOE BAT (RHINOLOPHUS HIPPOSIDEROS) IN BRITAIN AND IRELAND CAROL WILLIAMS1*, LEO SALTER1 and GARETH JONES2 1Cornwall College, Camborne Pool Redruth Campus, Cornwall, TR15 3RD, U.K; present address: 10 Treveryn Parc, Budock Water, Falmouth, Cornwall TR11 5EH *Corresponding author, E-mail: [email protected] 2School of Biological Sciences, University of Bristol, Bristol, BS8 1UG, U.K 3The Open University, Walton Hall, Milton Keynes, MK7 6AD, U.K Received 8 September 2010; accepted 20 March 2011 ABSTRACT - The lesser horseshoe bat Rhinolophus hipposideros feeds regularly through- out the winter across its British and Irish range. During winter 1995/96 and 1998/99, in Cornwall R. hipposideros fed mainly on dipteran flies in the families Tipuli- dae/Trichoceridae, Sphaeroceridae and Mycetophilidae. Differences in dietary composition were found across the British and Irish range of R.hipposideros in winter, and these proba- bly relate to local habitat differences. Nevertheless, across sites Tipulidae/Trichoceridae were always the most frequently eaten prey in winter, with Mycetophilidae and Anisopodi- dae also eaten frequently. The ecology of the important prey families indicated the value of damp woodland with decaying wood and grazing animals, particularly cattle, for the winter foraging of R. hipposideros. Key words: foraging, faecal analysis, dipterans, conservation RIASSUNTO - Dieta invernale del rinolofo minore (Rhinolophus hipposideros) in Bre- tagna e Irlanda. Il rinolofo minore Rhinolophus hipposideros si alimenta regolarmente in inverno nel suo areale britannico e irlandese. Durante gli inverni 1995/96 e 1998/99, in Cornovaglia questa specie aveva una dieta costituita principalmente da ditteri appartenenti alla famiglie Tipulidae/Trichoceridae, Sphaeroceridae e Micetofilidi. Differenze nella com- posizione della dieta invernale sono state trovate attraverso il suo areale, probabilmente im- putabili alla diversità degli habitat locali. Tuttavia, nelle zone esaminate i Tipulida- e/Trichoceridae erano sempre le prede più frequentemente consumate in inverno, seguite da Micetofilidi e Anisopodidae. Tenendo conto dell‟ecologia dei ditteri maggiormente consu- mati, le aree invernali di foraggiamento del rinolofo minore erano indicativamente i boschi umidi con legno in decomposizione e animali al pascolo, in particolare bovini. Parole chiave: foraggiamento, analisi delle feci, ditteri, conservazione DOI: 10.4404/Hystrix-22.1-4498 INTRODUCTION pended in foraging. For small insecti- vorous bats the energetic costs of flying For an animal to feed successfully, the can be as high as 21 x their basal meta- amount of energy acquired from feed- bolic rate (Racey and Speakman 1987) ing needs to be greater than that ex- and 600 x higher than the energy con- 159 Williams et al. sumption in torpor (Avery 1985). Dur- and across the range in Britain and Irel- ing the winter period (from October to and. April) when insect abundance in tem- perate regions is reduced, bats enter hi- MATERIALS AND METHODS bernation (prolonged torpor). Hiberna- tion is punctuated by arousals from tor- 1. Faecal analysis por, although the frequency of arousal varies among species and individuals Faecal pellets were collected at fortnightly (Menaker 1964; Daan 1973; Funakoshi intervals from a R. hipposideros night roost and Uchida 1978a; 1978b; Ransome in a cellar/boiler room of a small manor house, situated at the head of a valley that 1990). The exact cause of arousal is leads down to a tributary of the Helford uncertain (Park et al. 2000) but temper- River, Cornwall (50° 7‟N; 5° 8‟W). The ature in the roost plays a part. Arousal collections were made, from the same site, can lead to foraging if temperatures are throughout two winters, 1995/96 and sufficiently high and if other climatic 1998/99. The boiler was in use during the conditions are suitable (Ransome 1971, study and resulted in temperatures in the 1990; Avery 1985; Duvergé and Jones range of 13°C to 18°C. Polythene sheeting 1994). was placed on top of the boiler and faecal Because insect activity, temperature pellets and any discarded insect fragments and bat arousal are correlated (e.g. (such as wings and legs) fell onto the sheet and were collected. From each fortnightly Jones et al. 1995), bats may feed more collection, a random selection of 20 pellets often in parts of Britain that are mild was taken for analysis. during the winter (see Ransome 2002). The pellets were left to soak in water satu- Cornwall is in the extreme south west rated tissue paper for at least 4 hours and of Britain, and experiences a maritime then added with a few drops of glycerine climate and Rhinolophus hipposideros into a petri dish to aid the separation of the (IUCN Near Threatened status) feeds fragments contained in the pellet” (Shiel et regularly throughout the winter. In al. 1997). Using a headless entomological coastal regions of Cornwall, winters are pin, the pellet was then gently teased apart in the glycerine until the fragments that it very mild with temperatures falling be- contained could be readily seen under a low freezing only infrequently (2-23 Brunel MX-7T low power stereomicros- days/winter with air frost, 1971-2000: cope (magnification x 40) once mounted on Meteorological Office, Exeter, U.K.), a microscope slide.. Under the microscope, and winter foraging by R. hipposideros all fragments were identified to order and is expected to be common. most to family (Tab. 1). The identification At present knowledge of the diet of R. was carried out with the aid of various hipposideros is restricted to summer handbooks and keys (Skidmore 1991; Un- feeding (Beck et al. 1989; McAney and win 1991; Chinery 1993; Shiel et al. 1997). Tipulidae and Trichoceridae have been Fairley 1989; Hollyfield 1993; Beck grouped together as it is only if antennal 1994/5; Arlettaz et al. 2000). None of sections are present that it is possible to these studies have examined prey taken distinguish between them, and their habitat during winter foraging. The work re- needs are largely the same. Similarly Chi- ported here addresses this situation by ronomidae and Ceratopogonidae have been the analysis of species diet in Cornwall grouped together. A list of all recognizable 160 Williams et al. Winter diet of lesser horseshoe bats sumption in torpor (Avery 1985). Dur- and across the range in Britain and Irel- families was made for each faecal pellet in Cornwall and therefore the results are ing the winter period (from October to and. and from this a percentage frequency of the not as comprehensive. The results are pre- April) when insect abundance in tem- prey families found could be calculated for sented as a total of all sites for Devon, perate regions is reduced, bats enter hi- MATERIALS AND METHODS each fortnightly period. Percentage fre- Wales and Ireland for winter 1998/99. quency is the number of occurrences of a bernation (prolonged torpor). Hiberna- category, divided by the total occurrences 1. Faecal analysis RESULTS tion is punctuated by arousals from tor- of all categories, multiplied by 100%. The por, although the frequency of arousal presence of moths (Lepidoptera) can be a Faecal pellets were collected at fortnightly In winter 1995/96, Diptera were by far varies among species and individuals source of bias because moth scales remain intervals from a R. hipposideros night roost the most frequently occurring order (Menaker 1964; Daan 1973; Funakoshi in the digestive tract for long periods (Whi- in a cellar/boiler room of a small manor (86%; Tab. 1). Sphaeroceridae (24%) and Uchida 1978a; 1978b; Ransome taker 1988; Robinson and Stebbings 1993). house, situated at the head of a valley that This could lead to an overestimation of the were the most frequent family, fol- 1990). The exact cause of arousal is leads down to a tributary of the Helford importance of moths in the diet if all pellets lowed closely by Tipuli- uncertain (Park et al. 2000) but temper- River, Cornwall (50° 7‟N; 5° 8‟W). The containing scales are counted. In this work dae/Trichoceridae (23%). Mycetophili- ature in the roost plays a part. Arousal collections were made, from the same site, in order to accommodate this problem only dae (12%) and Scathophagidae (11%) can lead to foraging if temperatures are throughout two winters, 1995/96 and a moderate to large amount of scales, or also occur in significant numbers. sufficiently high and if other climatic 1998/99. The boiler was in use during the scales along with other remains of moth Changes in diet were relatively small study and resulted in temperatures in the conditions are suitable (Ransome 1971, classified the pellet as positive for Lepidop- range of 13°C to 18°C. Polythene sheeting (Fig. 1a), though Scatophagidae be- 1990; Avery 1985; Duvergé and Jones tera. was placed on top of the boiler and faecal came scarce after the end of December. 1994). A reference collection of insects, caught in pellets and any discarded insect fragments Due to the large number (21) of catego- Because insect activity, temperature a similar habitat to that surrounding the (such as wings and legs) fell onto the sheet ries involved at a low occurrence, in and bat arousal are correlated (e.g. roost some 4.5 km distant from it, was and were collected. From each fortnightly Fig. 1 those below a percent frequency made using a suction trap. Trapping was Jones et al. 1995), bats may feed more collection, a random selection of 20 pellets carried out on an approximately fortnightly of 5% are shown in the „others‟ catego- often in parts of Britain that are mild was taken for analysis. basis (avoiding nights with rain) by a John- ry. In winter 1995/96, this includes during the winter (see Ransome 2002).