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BaTML Publications www.batml.org.uk Factors affecting the distribution of Pipistrellus pipistrellus and Pipistrellus pygmaeus in the Lothians region, Scotland Author: Sarah Clear* Dated: 1st November 2005 *Correspondence details: email: [email protected] Abstract Until recently it was believed that Bandit pipistrelle (Pipistrellus pipistrellus) and Soprano pipistrelle (P. pygmaeus) were one species, as such relatively little is known regarding factors that affect their distribution in the UK. The BATS and The Millennium Link project (BaTML) has been surveying different sites on the Union and Forth & Clyde Canals to assess use of these canals by bats. They found a higher incidence of Soprano pipistrelle relative to Bandit pipistrelle than expected. This paper reports on a study which aimed to determine whether the relative abundances of the two species of pipistrelle in woodland and parkland sites, away from the canal, are similar to the abundances found in the Union Canal area, and to determine what factors are affecting their distribution. Four non­canal sites were surveyed between July and September 2004. The data collected from these surveys was compared with four canal sites previously surveyed by BaTML. The results showed that Soprano pipistrelle was more numerous than Bandit pipistrelle at all of the non­canal sites, indicating a higher abundance of Soprano pipistrelle in the Lothian region. Key words: Bandit, pipistrelle, Soprano, bats, BaTML, Union, Forth & Clyde, canals, bat Introduction selection (Barlow, 1997; Russ & Montgomery, 2002) showing a greater preference for habitats Until recently it was believed that there was only a with water (Russo & Jones, 2003). Bandit single species of pipistrelle bat resident in Britain. pipistrelle, on the other hand, appears to be more of However, in the 1990’s, it was discovered that what a generalist, albeit including habitats associated was thought of, initially, as two phonic types were in with water. As such there seems to be differences fact two separate species of pipistrelle bat; the in the foraging behaviour and habitat use between Bandit (or Common) pipistrelle (Pipistrellus the two species (Davidson­Watts, 2004). pipistrellus), and the Soprano pipistrelle (P. pygmaeus) (Jones & van Parijs, 1993; Park et al., Available information indicates that the Soprano 1996; Barratt et al., 1997; Barlow et al., 1997; pipistrelle appears to be the more common of the Jones & Barratt, 1999). two species in the Lothians (Haddow & Herman, 2001), although there are also reasonable numbers of records for Bandit pipistrelle in the area. Since virtually all studies carried out prior to the split assumed that there was only one species, Typically, the Bandit pipistrelle echolocates, there are gaps in the knowledge regarding the emitting a frequency of maximum energy (FmaxE), distribution and ecology of these two pipistrelle at around 46 kHz, and Soprano pipistrelle at 55 kHz species in the UK. (Russ, 1999). This is very useful when studying these bats in a non­invasive way, using bat Both species are found throughout Britain and detectors, in that quite often it is possible to allocate Ireland, but the Soprano pipistrelle may be more pipistrelle bats encountered in the UK to one or abundant in the north and the Bandit more other of the two species. There is, however, a abundant in the south (Warren et al, 2000; considerable overlap (48 to 52 kHz) between the Altringham, 2003). This is consistent with findings two species in their frequency range (Russ, 1999; regarding the distribution of the two species in Altringham, 2003). As such on occasions certain Europe, which are sympatric over much of the area. bats cannot be easily allocated. The Bandit pipistrelle is the most common species in central Europe, however, it is rare in Scandinavia The BATS and The Millennium Link project (Mayer & von Helversen, 2001; Hulva et al., 2004). (BaTML) has been carrying out echolocation surveys at different sites on the Union and Forth & Soprano pipistrelle appears to be more of a Clyde Canals, during the period 2001 to 2004, to specialist in terms of habitat preference and prey assess use of these canals by bats (Middleton et Copyright © BaTML Publications 2005, www.batml.org.uk, ISSN 1750­0796 Volume 2 ­ December 2005 ­ Page 23 BaTML Publications www.batml.org.uk al., 2004). In particular they have concentrated on the canal). The sites were chosen so that they Daubenton’s bat, Bandit pipistrelle and Soprano would be similar in terms of habitat type, pipistrelle species. BaTML have found at most vegetation, altitude, rough location and degree of survey sites across the Central Belt of Scotland, human disturbance (see Table 1 and Appendix I for that there appears to be a much higher abundance details). A comparison of the relative abundances of Soprano pipistrelle relative to Bandit pipistrelle. of each of the pipistrelle species could then be made between the canal and non­canal sites. Aims and objectives Table 1: The paired canal and non­canal sites One of the questions that the BaTML findings Canal Site Non­canal Disturbance Non­canal posed was: Is the higher incidence of Soprano Site Level Site pipistrelle compared to Bandit pipistrelle due to Habitat Type different habitat preferences of the species, or is Slateford Corstorphine Disturbed Woodland the higher incidence of Soprano pipistrelle a Hill Urban reflection of their general, higher abundance in the Lothian area? Gogar Moor Gogarburn Relatively Woodland Bridge Golf Club undisturbed Rural The aim of our study was to determine whether the Winchburgh Dalmahoy Disturbed Parkland relative abundances of the two species of pipistrelle North Country Club Rural bat in woodland and parkland areas, absent of water features, are similar to that found in the Union Learielaw Cammo Relatively Woodland Canal area. If so, this would indicate a higher Estate Park undisturbed Suburban abundance of Soprano pipistrelle in the Lothian area, or if the relative abundances are different to Three nights data from each of the four canal those found in the Union Canal area, this would survey sites were selected at random from surveys indicate that the species are showing differences in conducted by BaTML during the period April 2001 habitat preference. to September 2004. The results of these surveys were collated/analysed by N Middleton (BaTML), The Null Hypothesis stated: (1) There is no (refer Appendix I). The four non­canal sites were difference in the relative distribution of the two selected, based on the following criteria; survey species between the habitat categories; canal sites had to be absent of any water features; sites versus non­canal, and woodland versus parkland. had to concentrate on Urban, Parkland and (2) The distribution of the two species is unrelated Woodland areas within 5 km of the canal corridor to habitat preference. but no closer than 2 km. Each site was visited during daylight hours in June, Materials and Methods so that habitat and Health & Safety assessments could be made. A survey transect, consisting of 10 Project Design designated points, was decided upon and a map of the transect with the designated points was made. The specific aim of this project was to determine The habitat and vegetation coverage was noted for differences in the relative abundance/distribution of each point within each transect. For a description the two species of pipistrelle between sites located of the non­canal sites please refer to Appendix II. on the Union Canal and non­water sites between 2 km and 5 km from the canal corridor. As such a comparison between data from the two areas would Survey Protocol and Data Collection Methods be required. To achieve this, data was collected from the non­canal sites adopting the methods In order to survey each site for bats we adopted a used by BaTML relating to the collection and method whereby they would be recorded using a analysis of data using a Time Expansion bat TED (Courtpan, Tranquility Transect). This would detector system (Middleton et al., 2005). allow the FmaxE to be determined during the analysis stage, using sound analysis software Four canal sites were selected from the 22 sites (Pettersson Elektronik AB, BatSound, V3.0) being monitored by BaTML (Middleton et al., 2004). (Middleton et al., 2005). In addition to the TED we Four non­canal sites were selected to be surveyed also used two heterodyne bat detectors (Magenta for this study to correspond with each of the canal Electronics, MK11A) in order to allow us wider sites. Each canal site was paired with a non­canal coverage and to direct the TED towards any bat site on the basis that the only difference between activity encountered. It must be borne in mind that them should be the presence of a water body (i.e. the object of these surveys was to encounter as Copyright © BaTML Publications 2005, www.batml.org.uk, ISSN 1750­0796 Volume 2 ­ December 2005 ­ Page 24 BaTML Publications www.batml.org.uk many bats as possible in order that a comparison of Results relative abundance, in percentage terms, between the two species, could be made. As such we felt it An index of activity was calculated for each species was acceptable to be pro­active in this manner. in each site, by calculating the average number of bat passes per hour (Law et al., 1998). A bat pass Each of the four non­canal sites were surveyed is defined as a sequence of three or more pulses three times between July and September 2004. (Law et al., 1998). The equation IBA = Bp/t was Full details of the survey dates are provided in used where; IBA = Index of Bat Activity, Bp = Appendix I. At the start of each night, survey forms Number of Bat Passes and t = Time of survey.

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