A summary of bat records for 2023
During the year 2720 bat records were accumulated, the second highest total since the Manx bat Group began compiling records in 1990. Records were collected from members of the public, often using the recording form on the group’s website https://manxbatgroup.org/manx-bats/records/submit-a-bat-record/ , from members conducting roost counts, surveys or transects and from surveys conducted by the group or others in connection with planning applications. Such records are largely derived from acoustic recordings and the bat species are identified from sonograms on a computer. Given that bats hibernate there are few records for the winter months and the five months May to September account for 88% of all records.
Negative records
Negative records are generated when a roost or a bat box is checked with no bats found in residence. There were 7 negative records this year involving 11 bat boxes, 6 of them twice, and three roosts. One of the roosts had no bats on both dates it was checked.
Vespertillionidae
There were 31 records where the species of bat was not determined. These are usually submitted by members of the public who just report seeing a bat or, in rare cases, 8 records, where bats are seen in hibernation and cannot be disturbed to elucidate their distinguishing features. 3 of the records referred to bats seen in previous years and 5 to active roosts. 6 records were of bats flying around the lighthouses on the Calf of Man or Cow Harbour. One record was of a dead bat found on the pavement at Bishop’s Dub.
Myotis species
There are three species of bat in the Isle of Man in the genus Myotis. Sometimes a recording will not show the characteristic features necessary to identify it to species level and records are therefore assigned to Myotis species. There are 285 such records, 10% of the total, but nearly all of them were gathered during surveys when other recordings were able to be assigned to species. Two of the recordings involved social calls.
Pipistrellus species
The three species of Pipistrellus bats on the Isle of Man are usually told apart by the frequency of their calls, although there can be some overlap between them. In that case records are assigned to Pipistrellus species but more usually it is their social calls that are more difficult to assign to species. Of the 187 records of Pipistrellus species 148 involve social calls. These are most frequently encountered in late summer when young of the year begin accompanying their mothers on foraging flights but can also involve inter- and intra-specific encounters and mating behaviour.
Lesser horseshoe bat Rhinolophus hipposideros
The Manx Bat Group continued its efforts to locate this recently discovered species. It has a very quiet call, however, and has to pass close to a detector, reportedly within 5 m, to make a recording so all recordings are relatively fortuitous. All 9 records this year were obtained at the Chasms in surveys running from February to May.
Daubenton’s bat Myotis daubentonii
There are similar numbers of records of Daubenton’s bat (116) and Natterer’s bat (136) but for perhaps different reasons. Natterer’s bat has a low volume call and needs to be close to the detector to make a recording. On the other hand, Daubenton’s bat is traditionally regarded as a species frequenting still waters as it hunts emerging aquatic insects and, therefore, a habitat specialist. 82 of the records collected in 2023 were from acoustic surveys conducted over two or more days only half of which were from what would be regarded as classic riverine sites where Daubenton’s bats might be expected. These include Glen Maye, Glen Grenaugh and the Neb valley between Glenfaba bridge and Peel harbour. Surveys were also conducted on some upland sites, starting with Creg y Cowin, the new Manx Wildlife Trust reserve, and these provided records of Daubenton’s bat even as high as Brandywell. Most of the 17 such records were from late summer into autumn and might reflect movement of this species to uphill (hence colder) sites such as mine adits for hibernation. 30 records probably associated with a hibernation site were also obtained during surveys at the Chasms from February to May. Other interesting records were obtained from surveys at Ramsey Woods MWT reserve, Gordon in Patrick, the mouth of the Lhen Trench and South Harbour on the Calf of Man.
Natterer’s bat Myotis nattereri
There were 10 records of Natteer’s bats collected during surveys for planning purposes with the remaining 126 all collected during acoustic surveys of potentially interesting sites, ranging from Manx Wildlife Trust lowland and upland nature reserves, Areas of Special Scientific Interest and Manx National Heritage land at the Chasms. Surveys were carried out at the Chasms from February through to May and resulted in 60 records, with most recordings obtained in March. It is assumed that the winter hibernaculum (if such there is) broke up slowly after that although some recordings were still being obtained in the first half of May. Conditions at the Chasms are conducive to obtaining recordings since the bats have a restricted flying space in the underground cracks and, if present, have to pass close to the microphone. It is interesting, therefore, that numerous recordings were obtained at the new upland reserve of Creg y Cowin, in an open landscape, and also at Dalby Mountain Meadow reserve and even at the Brandywell marshal’s shelter on the Mountain course. These were all in the second half of the summer, late July, mid-August and early September. Records were also obtained form Cooildharry MWT nature reserve, Ramsey Woods and Glen Maye, all woodland sites more often associated with this species.
Whiskered bat Myotis mystacinus
There were 214 records of Whiskered bat, 8% of the total, indicating that this species was encountered rather more often than either of the two previously discussed Myotis species. In addition to all the sites mentioned for those species it was recorded at three locations in Lough Cranstal MWT reserve, at the Raggatt, Garwick Glen, Glenfaba bridge, Billown, Tholt y Will and the garden at The Old Chapel, Jurby East.
Brown long-eared bat Plecotus auritus
This is another quiet species but there are more records for it than any species previously discussed, 258, or 9% of the total. 16 of the records are of roosts, either actual counts or observations of bats emerging from a roost (11), or returning in the early morning (2), or one or two individuals taking shelter (3). Records were obtained during 8 surveys conducted for planning purposes involving land on the edges of Douglas, Ramsey and Peel, along with several large houses in the country. Long-eared bats were recorded at many of nature reserves already mentioned, including Creg y Cowin in late August, but also Brandywell in September while records in early Spring were obtained at the Chasms.
Leisler’s bat Nyctalus leisleri
18% of the records are for this, our largest, species of bat. It is a strong, high-flying bat with a loud call, capable of being recorded at 100 metres or so distance so it is no surprise that it is recorded during almost every acoustic survey and in every corner of the Island. However, only a few roosts are known and records were obtained from only two roost counts, one on the edge of Douglas and at a newly discovered roost near Sandygate. It was recorded during 15 planning surveys, and during acoustic surveys at 8 nature reserves (including the Chasms) and 4 bat walks. It was also recorded during beach surveys in the north, at 10 locations, and even flying out over the sea at one location south of Laxey.
Nathusius pipistrelle Pipistrellus nathusii
First recorded in 2018, the most records for this species were obtained during a survey for planning purposes just south of Peel, alongside the river, on six dates in early July. It was, however, also recorded in every month from April, at Lhen bridge, to October when it was recorded at the Manx Birdlife reserve at the Point of Ayre. In between it was recorded in various locations around the Island, including Sulby Glen, Smeale and Lough Cranstal in the north, Cooildharry, Peel Hill, Gordon and Dalby Mountain Meadow in the west and Ballanard Woods and Laxey Salmon Centre in the east.
Soprano pipistrelle Pipistrellus pipistrellus
It has been observed previously that that Soprano pipistrelles are infrequently encountered south of the central hills and only 30 of the 226 records for this species are from the ‘south’, south and east of the line from Cronk ny Arrey Laa to Maughold Head. 8 of these were obtained during surveys at the Chasms in April and May. Only one maternity roost of this species was counted, on two occasions in June with 155 bats emerging on the first occasion and 181 on the second. This species was recorded during roost counts for other species, on five occasions from Silverdale and the Raggatt to Lezayre church and Andreas while there was one record, in mid-March of an individual hanging on the back of a painting in an empty outbuilding in Baldwin. 79 records were obtained during 12 surveys for planning purposes. These surveys were carried out in Arbory, Braddan, Castletown, Douglas, Lezayre, Malew, Maughold, Michael, Patrick Peel, Ramsey and Rushen but only 8 records were from the ‘south’. 101 records were made during site surveys of 17 different sites and 7 beaches. The sites included all those previously mentioned but also the Raggatt and Narradale, Jurby East garden, Rue Point and the Ayres. The beaches survey was specifically conducted to ascertain the relative importance of autumn beach foraging for soprano pipistrelles and comprised 1 km transect along beaches from the Lhen to Ballaghennie. While each transect only made for one record the number and proportion of soprano pipistrelle recordings, compared to those for common pipistrelles, ranged from a high of 138 (81%) at the Lhen to 3 96%) at Ballaghennie. Other transects were carried out by Bat Group members, often close to home, for example at Polly Road, Jurby, Port Erin golf course, Surby, or at hotspot sites such as the Curraghs. There were 24 such tranects in total.
Common pipistrelle Pipistrellus pipistrellus
There are 755 records of Common pipistrelle constituting 28% of all records for the year. This percentage has hardly changed in the years since 2018, the first year Anabat Express detectors were started to be used extensively to record bats on the Island. Prior to that, common pipistrelle records were as high as 45 % of all records, in 2015. This species was recorded in every month, apart from December and in every parish. Counts were conducted at 11 maternity roosts and 23 specimens were brought to the attention of the bat care team via the Bat Helpline (tel 366177). Sites surveyed include all those mentioned above but notable records, involving over 650 recordings per night, include the wood at Creg y Cowin nature reserve and a private garden at the Lhen bridge, on four occasions each. Nearly as many recordings were obtained in Jurby East garden on September 2nd, 559, and 5 days later over 100 social calls attributable to Common pipistrelle, were recorded on each of two detectors. This probably indicates mating behaviour of males calling to attract females.
With thanks to those volunteers who deployed and retrieved all the bat detectors, often involving considerable physical effort, the Bat Care team and the members of the public who reported bats via the Bat Group’s website.