Brown Long-eared Bats Plecotus auritus are one of our most distinctive bats; they are a medium-sized bat with very long ears, which are at least 28 mm long and approximately 75% of their body length (Harris and Yalden, 2008). When they are active and their ears are erect they have a distinctive shape. Brown Long-eared Bats can also hold their ears partially erect, like rams’ horns. They generally fold their ears and tuck them under their wings when at rest or hibernating leaving the long tragus projecting forward. The only similar species occurring in Britain is its close relative, the Grey Long-eared Bat Plecotus austriacus whose range is restricted to the very southwest of England. Brown Long-eared Bats were present in Britain in the Pleistocene and they have been recorded from Westbury-sub-Mendip, Somerset, in the mid Pleistocene and Dog Hole Fissure, Derbyshire, in the Mesolithic era (Harris and Yalden, 2008).
Brown Long-eared Bats emerge in low light levels or even complete darkness. Their echolocation calls are very quiet and the calls can be emitted by the mouth or through the nose. They have two main strategies for capturing prey: they either catch insects in flight using echolocation calls or glean prey from foliage or other surfaces by listening for movement. Around half the captures are of insects in flight and half by gleaning (Harris and Yalden, 2008). The proven maximum age for a female Brown Long-eared Bat is 30 years, with an average life span of four years (Dietz et al. 2009).
Brown Long-eared Bats in western Europe prefer to roost in buildings during summer and hibernate underground (Dietz et al., 2009). Summer roosts have also been recorded from trees and bat boxes and they are known to use the same roost for generations. Nursery colonies comprise closely related females and these bats can inhabit a territory as small as approximately one km2 over decades (Dietz et al. 2009). These figures are comparable to the data given by Harris and Yalden (2008) that Brown Long-eared Bats forage close to their roosts, within 1.5 km of the roost site and often within as little of 0.5 km. Brown Long-eared Bats are woodland specialists, foraging under tree cover but also around individual trees in parks and gardens and their roosts tend to have a strong association with tree cover.
The size of Brown Long-eared Bat colonies is generally smaller than for the other British bat species. Swift (1998) recorded colony size as averaging 20 bats in wooded valleys in central Scotland, with a maximum number of 47 bats. This is similar to that given for a range of studies (Ibid). In Northumberland the maximum colony size so far recorded is of 50 bats, from three separate locations, but the largest colony recorded in Durham, of 114 bats from a cottage in Knitsley, is exceptional by most standards.
A small number of hibernacula are known to the west of County Durham and a single bat was found hibernating in the cellars of Gibside Hall in 2007; a summer roost of at least seven bats was found in the stables at Gibside in 2011. The largest hibernation roost so far recorded in the region is of 37 bats in a house at Haltwhistle. They prefer lower ambient temperatures for hibernation than most European bat species (Swift, 1998), which might explain why two Brown Long-eared Bats were found hibernating behind flaking bricks in a tunnel at Boulby, a very exposed location (Ian Bond, pers. comm., Sept 2012).
Mennell and Perkins (1864) and Bolam (1926) mention Brown Long-eared Bat, respectively describing it as “generally distributed and abundant in Northumberland and Durham” and “in our counties it seems to be everywhere common, though not noted anywhere as occurring in such numbers as either the Pipistrelle, Daubenton’s or the Whiskered Bats”. Bolam goes on to say it is occasionally seen around Alston “and it has been found as high up the valley as Skydes”, where one was found hiding in a crevice in “Jackdaw Rocks” while the finder was looking for Jackdaw Corvus monedula nests. The fact that neither of these authors spent any time describing the Brown Long-eared Bat emphasises how well known the bat was at that time.
Brown Long-eared Bats are still considered to be one of our most common bat species; they are a more rural bat and avoid urban centres as can be seen on our distribution map. At the time the Distribution Atlas of Bats in Britain and Ireland 1980-1999 was published (Richardson, 2000) the records for Durham were almost exclusively along the middle stretches of the Tees and Wear. Our current understanding of Brown Long-eared Bat distribution is very different: within County Durham the distribution of Brown Long-eared Bat does show a degree of apparent correlation with river valleys as in 2000, but this now also includes groups of records on the Browney, the Deerness and Bedburn Beck. However this may not be a true association, as it is possible that Brown Long-eared Bats show an association for the type of woodland that is mostly, but not exclusively, found along river corridors. In Northumberland Brown Long-eared bats are present throughout most of the county and the known distribution is strongly correlated to river corridors. They have been the second most frequently recorded species in Northumberland according to Northumberland Bat Group records (Ruth Hadden, pers. comm., Sept 2012).
The maps in Richardson, (2000) did not show any records for Cleveland as there was no Cleveland Bat Group at that time to provide them, though Wardhaugh (1994) stated “Eleven roost sites have been located, eight of these being in loft voids of sandstone or brick houses or similar buildings where up to about 30 individuals have been noted at a number of sites during the Summer.” Except for the largely inter-tidal and built up stretch of the River Tees most water courses in Cleveland are small, so there is no noticeable association with water, though there would still appear to be a very close association with woodland.
Brown Long-eared Bats have a preference for roosting within older, grander buildings. A list of Brown Long-eared Bat roost sites can read a bit like a rural version of Who’s Who with the buildings including halls, granges, manors, castles and churches. By contrast, in October 2003 a small colony moved into the gents toilet block at the Wynyard Woodland Park, Stockton, after a window had been broken. Clearly slumming it, a group of five bats hung high on the wall above the wash basin with a lone individual above the urinal (Ian Bond, pers. comm., Sept 2012)! Brown Long-eared Bats are roost faithful and this may also influence their choice of roost site as these buildings are older and well established. A study by Wardhaugh (1994) based on the eleven records above, concluded that buildings used by roosting Brown Long-eared Bats are “generally of the order of 100 years or more in age” in contrast to buildings used by pipistrelles; in the same study he found that 74.4% of pipistrelle roosts were in houses less than 25 years old.
Although Brown Long-eared Bats nearly always roost in older buildings a roost of at least four was present in a black painted corrugated metal shed during the summer of 2007 and the bats could be seen dropping out under from a corrugation just below the apex and were present all summer (author’s own data, 2012).
Brown Long-eared Bats will also readily use bat boxes. In the Hamsterley Forest bat box scheme Brown Long-eared Bats have been found in 13 years out of 22, including examples of maternity roosts. The largest annual total was in 1992, when 18 bats were found in one box and 13 in another. Single Brown Long-eared Bats have also been found on at least three occasions in the Low Barns bat box scheme. Brown Long-eared Bats are encountered in Dormouse Muscardinus avellanarius boxes at Allenbanks, two males were found in the same box in July 2001 and a single bat (sex unknown) was found during checks this summer (2012).
It is not unusual for Brown Long-eared Bats to be found in a roost also used by other species. At Mount Oswald Manor, Durham, and at Hamsterley Hall, Common Pipistrelle Pipistrellus pipistrellus, Soprano Pipistrelle P. pymaeus, Natterer’s Bat Myotis natttereri and Brown Long-eared Bat have been recorded using the same building, although the roost locations and exits have been different for each species. In the Allen Valley, in Northumberland, Brown Long-eared Bats have been recorded roosting in the same loft space as Common Pipistrelle, Soprano Pipistrelle and Natterer’s Bat with all bat species forming separate clusters. In a tunnel under the Hart to Haswell Tunnel in Hartlepool they use the same cracks in the ceiling as Natterer’s bats, also in separate clusters but with both species as close as one metre apart. Brown Long-eared Bats have been recorded in the tunnel since 2001 and surveys have shown that at least a small number of individuals are present throughout the year (with a maximum number of 21 in September 2001), but due to the depth of the cracks the numbers could be significantly higher than those that are counted (Ian Bond, pers. comm., Sept 2012).
Written by Tina Wiffen (last updated Nov 12)