Originally published in Peregrine, 10(6), pp 714 – 712 in 2018, the collection of a total of 2106 records to the end of 2015 includes some eighty-six records amassed from the literature and personal records for the period before the Manx Bat Group was formed.
The first date given in the literature for a named species of bat, for pipistrelle (Pipistrellus pipistrellus sensu lato (Schreber, 1774)), is January 1848 in a list of phenological observations given by P.M.C. Kermode to the Isle of Man Natural History and Antiquarian Society (Kermode 1889a). P.M.C. Kermode was a remarkable man, a lawyer by profession but a dedicated and accomplished antiquarian eventually becoming the first Director of the Manx Museum. He was also an accomplished naturalist, publishing many observations on the birds and mammals of the Isle of Man. He evidently even kept bats as pets, and described them as easy to tame, feeding one of them by holding it up to the window to take flies. In 1916 he also called for attempts to be made to find Leisler’s bat (Nyctalus leisleri) and whiskered bat (Myotis mystacinus) in the Island as he felt they should occur here on the grounds that they were to be found close by in the adjacent islands (Kermode 1912-25).
The brown long-eared bat (Plecotus auritus) was not, at first, known to Kermode although he thought it had been taken in the island. It was not until 1885 that he saw his first specimen, taken by Mr H S Clarke at Bride Church in September of that year (Kermode 1889b). Remarkably, this species is still to be seen at Bride Church along with common pipistrelles which also reside there. Another early stalwart of the Society, J. C. Crellin, described the pipistrelle as the “common small bat” a few years later but gave a location, and hence the first localised record for this species, Sulby village (Crellin 1901).
Today, what Kermode and Crellin referred to as the common bat (pipistrelle) is now known to be two distinct species. The common pipistrelle, Pipistrellus pipistrellus (Schreber, 1774), and the soprano, or pygmy, pipistrelle, Pipistrellus pygmaeus (Leach, 1825) were separated in 2003 on morphological, behavioural and genetic grounds (Int. Comm. Zool. Nomen. 2003). However, since the primary means of distinguishing the two species is the frequency of their echolocation calls, and the Manx Bat Group organised a bat detector workshop in 1997 (Manx Bat Group 2000), it is possible to assign a first record date of June 1997 to both these species.
Kermode’s hope, to find whiskered bats (Myotis mystacinus), was not to be realised for nearly thirty years until R. Wagstaffe, Keeper of the Yorkshire Museum, visited the island. A report on this visit was not published, however, for another thirty years (and not known in the island for a further ten) and contains no date for his visit (Wagstaffe 1979). Wagstaffe did publish his finding of another species on the Isle of Man, Natterer’s bat (Myotis nattereri), on the 17th July 1944, grounded outside an outhouse in Ballaugh, (Wagstaffe 1945). The assumption is that his whiskered find, in the tower of Braddan Old Church, along with many Natterer’s and a few brown long-eareds, was around the same time (Garrad, pers. comm.). And yet his Peregrine report, submitted over a year after his visit, contains another plea to look for whiskered bats, along with Daubenton’s and Leisler’s, with no mention of his finding whiskered bats at Braddan Old Church, so at present one must conclude that his whiskered find was post-1945 at the least. What is surprising is that Wagstaffe, a Museum professional who had published a first record of one bat species, appears never to have published the first record of another bat species which he had explicitly stated should be sought out.
The next new species was in 1961 when Gordon Craine caught a Daubenton’s bat (Myotis daubentonii) in a mist net on the Calf of Man. There were no records of this species on the main body of the Isle of Man, leading many to suggest that Craine’s specimen must have been on migration, like so many of the birds that the mist net was employed to catch. Ten years later Larch Garrad (1972) stated that there were three species of bat in the Isle of Man, pipistrelle, (brown) long-eared and natterer’s, and she refers to long-eareds being caught in mist nets on the Calf of Man on several occasions. She appears not to have known about Wagstaffe’s’s article, in a rather parochial journal, until 1987 (Garrad in litt.) and so Cullen and Jennings (1986) repeated Garrad’s short inventory of three species. However, when Wagstaffe’s article came to light, correspondence with Bob Stebbings, the leading UK bat specialist, enabled him to quote four species present in the Isle of Man (Stebbings 1988), adding whiskered bat to Garrad’s earlier three. Stebbings goes on to reveal the fate of the remarkable colony of bats discovered by Wagstaffe, poisoned by the church authorities at some time in the 1960s.
Daubenton’s bat was not confirmed on the Isle of Man until 1990 when two specimens were located hibernating in stonework on the underside of a bridge at the lower end of the Baldwin valley. This record was published in Pinder & Bolton (1990) along with one for the other long-sought species, Leisler’s bat, found grounded in Bishopscourt chapel.
Since then nearly 2000 records have been added to the data base maintained by the Manx Bat Group, with one further addition to the Manx bat fauna. A rather distinctive looking bat was found grounded outside a house in Glen Chass in November 2006. Richard Selman took careful notes from the finder and concluded that it was a lesser horsehoe bat (Rhinolophus hipposiderus) and later published his conclusion (Selman 2014). For the time being, until any further reports materialise, it is considered that this has the same status as the Daubenton’s bat caught on the Calf of Man, ie it was an individual migrating bat, although it should be borne in mind that the Manx Bat Group has had several anecdotal, historical reports of bats in sea-caves matching the description of lesser horseshoe bat.
Out of the total 2106 records, almost exactly half are not assigned to species level, being recorded as either Vespertilionidae (vesper bat, the family to which all our species belong) or Pipistrellus sp. This is because the Manx Bat Group encourages submission of records from the public, who may not have the skills or equipment to make a species identification. The records are, however, valuable in assisting the build-up of knowledge of the distribution of bats in the island. Most of the Pipistrellus sp. records either predate the split in taxonomy or have been made by persons familiar with the flight patterns of pipistrelles but without a bat detector at the time of the observation.
Bat detectors have transformed the study of bats in permitting identification of live animals in the field, in a non-invasive way. Previously, bats had to be caught and examined in the hand but now bat detectors permit an experienced operator to make an identification on nearly every occasion, although separating Myotis species is said to be virtually impossible. Detectors are now becoming available that show sonograms of the bat’s ultrasonic calls in real-time while some models also use analytic algorithms to make their own identification.
There are in total 999 records for pipistrelles, either the two distinct species or the aggregate Pipistrellus sp. which would seem to confirm the perception of most observers that pipistrelles are the commonest bat species on the island. The total is made up of 702 Pipistrellus records, 255 records for Pipistrellus pipistrellus and 42 for P. pygmaeus.
Of the 1060 records to species level, those for the brown long-eared bat are the most common, with 334 records, again possibly confirming observers’ perceptions. Leisler’s bat is the only other species for which there are over a hundred records (144) with Natterer’s the next most frequent on 97. Then follow the other two Myotis species, Daubenton’s and whiskered with 83 and 50 respectively, while unidentified Myotis sp. comprise 53 records. Then follows P. pygmaeus with only 42 records and the list is completed by the single lesser horseshoe record discussed above.
To some extent the frequency distribution of bat records probably does reflect the relative population levels of the various species but not with any degree of accuracy. All surveys contain biases as is illustrated by the data set generated by vehicle-based transects conducted by the Manx Bat Group each year from 2006 to 2008 (see table below). The first and most obvious bias is that none of the eighteen surveys conducted over the three years recorded brown long-eared bats, because they are the quietest species, often undetected by a heterodyne bat detector while the operator can see them only feet away. These surveys actually used a time-expansion bat detector connected to a digital recorder for later computer analysis but even this failed to record any long-eared bats.
Another bias in transect surveys is the probability of encountering a bat, depending on its behaviour. If bats followed the same route on their foraging journeys, spending the same amount of time at the same places, this bias might be minimised but bats are real animals and so alter their behaviour in accordance with prey availability, weather and so on. This can be seen in the table below where the number of bat encounters per driven transect varies enormously from year to year. This variation is even more extreme when one considers the one transect common to each year’s survey effort.
| All transects | Common transect #5 | ||||||
| Year | 2006 | 2007 | 2008 | 2006 | 2007 | 2008 | |
| No of transects | 10 | 4 | 4 | ||||
| Unidentified Bat | 31 | 13 | 2 | 1 | 7 | 0 | |
| Myotis Bat species | 16 | 0 | 0 | 2 | 0 | 0 | |
| Pipistrelle sp | 30 | 15 | 2 | 3 | 9 | 0 | |
| Soprano Pipistrelle | 17 | 5 | 0 | 0 | 2 | 0 | |
| Leisler’s | 27 | 18 | 10 | 1 | 6 | 8 | |
| Common Pipistrelle | 314 | 120 | 109 | 26 | 53 | 43 | |
The one clue we do have as to relative population levels is from a Master’s student thesis for which the field work was conducted in 2003. Jenny Dunn (unpublished thesis 2002) walked forty two transects between June and September 2003, recording 693 passes by Pipistrellus pipistrellus, 49 P. pygmaeus, 30 indeterminate Pipistrellus spp., 52 Myotis spp., and 3 Nyctalus leisleri. P. pipistrellus was considerably more common than P. pygmaeus with an average of 4.91 bats per linear km compared to 0.35 bats per linear km for P. pygmaeus. Dunn compared the number of bat encounters per kilometre with results from a study in the United Kingdom (Walsh et al 1995) and found bat abundance to be over five times greater than that predicted by Walsh et al’s methods and twice that detected in Northern Ireland by Russ et al. (2003).
If the records are unable to provide any precision as to the relative population size of the different species, neither do they provide much precision to their distribution. Two parishes (Lezayre and Braddan) contribute just over twenty per cent of the records. Sixteen districts have fewer than 100 records whilst over half of the records are provided by the 6 districts (one quarter) with the most records. This disparity will reflect observer effort with Braddan, Douglas and Marown, with the larger human populations, being in the top six along with the known bat hot-spots of Lezayre and Patrick.
The distribution of bats, as a whole and as individual species, will become more evident when the data is visible on the forthcoming NBN Atlas Isle of Man, an initiative of the Manx Biological Record Partnership. At present, all that can be said is that Dunn’s observation that the majority of observed bat passes for P. pygmaeus were restricted to the glens to the south of Ramsey has proven too restrictive as they have now been found even in some of the southern parishes. Leisler’s bat records are also much more widely distributed, and frequent, than indicated by Dunn’s results.
Nearly a quarter of all records, 506, refer to maternity roosts, sites where female bats congregate to have their young in summer. These concern some 207 known locations, usually houses but including several churches, some utility sub-stations, a couple of schools and even several trees. One was found in a telegraph pole as it was being replaced and the workers kindly left the sawn out section with the roost hole strapped to the replacement post.
There are more roosts known for brown long-eared bats than any other species, with 44, but if unspecified pipistrelle roosts are lumped together with common pipistrelles (as they probably are) then a total of 93 of these roosts have been identified. As may be expected these far outnumber those known for other species with only 11 roosts known for Natterer’s bat, and 9 and 7 for whiskered bats and Leisler’s respectively. Five roosts are listed for Soprano pipistrelles and two possibilities for Daubenton’s bat. Although this latter species was seen returning to locations at dawn the actual roost site was not found.
The Bat Group had a monitoring programme in place for its known roosts for many years, asking owners to return a postcard, preferably with a count or at least an indication of occupancy but received a very variable quality of return. The best monitored roost was counted for 18 years, up until 2010, but has recently been reported as being absent for the last two to three years. Only four other sites were monitored in more than ten years while, unfortunately, 113 were only reported once. Roost sizes vary between species with pipistrelles typically congregating in the largest numbers, averaging 100 – 200 in Scotland where, exceptionally, colonies may contain over a thousand individuals. No known Manx roosts attain this size and the highest count made by the Manx Bat Group was 201 individuals. Several other roosts have attained numbers in excess of 100 but the majority are below this.
The next largest roost known is for Leisler’s bat with a count of 70 while Natterer’s and whiskered bat come in at 49 and 36 respectively. That is to be contrasted with Wagstaffe’s account (1979) of a visit to a church tower near Douglas, thought to be Braddan Old Church (which has since been altered, Garrad pers.comm.). He says, “When we opened the door we disturbed many thousands of bats…..hanging like swarms of bees….twenty to thirty swarms”. Wagstaffe and his friends then caught one swarm in a butterfly net and counted the contents which amounted to 700 Natterer’s bats, a number of whiskered bats and a few long-eared bats. Multiply that by twenty and a staggering total is attained – 14,000 Natterer’s bats. He reported that neither of them had ever experienced anything like this before or since and no roosts of this size have ever been reported from the United Kingdom.
Although not necessarily visited on an annual basis some of these roosts are long-standing. The long-eared bats still roost at Bride Church a hundred and thirty years after the first specimen was taken there and pipistrelles have been known to roost there for 54 years. Nevertheless, only 34 roosts have a known history greater than ten years while 29 roosts are feared to have been lost. This is most likely through inappropriate re-development or building alterations but it has to be said that in some cases roosts move of their volition. There is one, relatively new, estate in the western outskirts of Douglas where at least four houses seem to host a common pipistrelle roost at different times during the summer while not too far away Leisler’s move around five houses in a different estate with a further roost in Union Mills probably part of the same extended colony. Unless the recorder is aware of these satellite roosts it is difficult to be certain, therefore, whether a roost has been abandoned when a zero count is made or whether the bats have just switched location temporarily. However, the records indicate that only one roost had the highest count for two consecutive years and one other had the maximum count for four out of the 25 years under consideration. This latter roost was regularly counted between 1995 and 2010 and had four counts of few or zero bats. Evidently, roost switching is a fairly common event.
P.M.C. Kermode told us (Kermode 1889c) that in Manx folklore the bat is one of the Seven Sleepers (the others being the butterfly, bee, lizard, cuckoo, wheatear and the swallow). Nevertheless he reported seeing bats flying in November, December and February and the Bat Group likewise have records of bats flying out of season. A total of 91 records are dated between November and February when bats might be thought to be hibernating and 37 of these show that bats were active, either seen feeding (including a few observations in the daytime) or found in places where they must have recently arrived.
Only a very few of the winter records are from what might actually be considered hibernation sites in rockwork, stonework or trees. The Manx Bat Group has conducted several seasons of winter surveys of potential hibernation sites with limited success; two bats were found in the Chasms, two in Laxey mines and one at Beckwith’s mine, while only three have ever been found under bridges. In total, thirty-five records indicate features of a hibernation site but they are all single records and none of the sites have been re-visited. However, the fact that 11% of the records occur in the winter months does suggest that our bats stay here rather than migrate off-island .
The final consideration is the acquisition of records. As stated earlier, submission of records from the public is encouraged and many are received in this way. Some result from bats being regularly seen in someone’s garden or else a specimen being found grounded or presented by a household pet. 74 records, nearly 3.5%, are classed as cat casualties, and one dog, only some of which could be nursed back to health and released. At least four records have arisen as bats have collided with vehicles, two being pinned to the radiator grilles, one of these being on a fire engine. But the most remarkable record was of a pipistrelle found pinned to the radiator grill of an aircraft at Ronaldsway airport.
The majority of records come from members of the Manx Bat Group, either as a result of concerted group effort surveying a particular district or individual activity. The number of records is set to rise substantially since the Bat Group now has access to recorder detectors, some with in-built GPS function, which can be analysed on a computer after the survey is completed. For 2015, the last year under consideration in this present article, 60 of the 183 records were generated in this manner, whereas the average for the previous years was around 100 records a year. They may even provide records of new species for the Manx list, such as the lesser horseshoe bat or Nathusius’ pipistrelle which likewise occurs in Northern Ireland and increasingly in England. The Manx Bat Group has now initiated an annual survey for Nathusius’ pipistrelle and is actively pursuing a programme of annual monitoring to inform the Manx Biodiversity Planning process so is seeking more members and volunteers to assist. Further details, including membership, are available on the website www.manxbatgroup.org.