A summary of bat records for 2024
It is considered that not all bat records for 2024 have yet been collected and compiled but by the end of the year 2490 records had been added to the database.
| 2020 | 2021 | 2022 | 2023 | 2024 | change | |
| Pipistrellus pipistrellus | 28% | 29% | 27% | 28% | 31% | Slight increase |
| Nyctalus leisleri | 18% | 16% | 16% | 18% | 15% | Slight decrease |
| Myotis species | 5% | 7% | 10% | 10% | 12% | Increase |
| Pipistrellus pygmaeus | 15% | 9% | 10% | 8% | 8% | Decrease |
| Myotis mystacinus | 14% | 12% | 10% | 8% | 7% | Decrease |
| Myotis nattereri | 4% | 6% | 5% | 5% | 7% | Stable |
| Plecotus auritus | 8% | 6% | 6% | 9% | 7% | Stable |
| Myotis daubentonii | 3% | 3% | 5% | 4% | 6% | Slight increase |
| Vespertilionidae | 2% | 3% | 1% | 1% | 2% | Stable |
| Pipistrellus species | 1% | 8% | 7% | 6% | 2% | Varying |
| Rhinolophus hipposideros | 1% | 0% | 0% | 0% | 1% | Stable |
| Pipistrellus nathusii | 0% | 0% | 1% | 1% | 0% | Stable |
| Myotis total | 26% | 27% | 30% | 28% | 33% | Increase |
In percentage terms there have been subtle changes in the number of records of the various species which possibly reflects survey effort and record-keeping methodology. There was a concerted effort to survey for Daubenton’s bats while pipistrelle social calls were more frequently assigned to species where only one species was present.
Negative records
Negative records are generated when a roost or a bat box is checked with no bats found in residence. There were 11 negative records this year involving 30 bat boxes in 9 locations. In addition two roosts had no bats emerging while being counted as part of the National Bat Monitoring Programme (NBMP).
Vespertillionidae
This year there were 62 records where the species of bat was not determined. Such records are usually submitted by members of the public who just report seeing a bat. 15 records were of bats on the Calf of Man or Cow Harbour. Five were of cat casualties, one of which flew off, as did 4 others encountered indoors by members of the public. Bat boxes at three sites were occupied by bats which could not be disturbed for positive identification. At Colden plantation where the bat boxes are all of the wooden Kent style there were 2 in one box and one in another. At Glen Helen there were two in a flat wedge Schwegler box and at Colby Glen in December there was one in one Schwegler pot type box. Four findings of droppings indicated new roosts, only one of which was confirmed.
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 304 such records, 12% of the total, but nearly all of them were gathered during surveys when other recordings were able to be assigned to species. 10 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 42 records of Pipistrellus species, 19 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. 9 records are from the Calf of Man. Other records were collected during 9 different acoustic surveys and two historic records of presumed roosts.
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. None were recorded during spring surveys at the Chasms and the first of the year was in June at the bridge along Kentraugh back road. In August 3 records were obtained by the river west of the bridge with a further record in September in a field alongside the river south of Kentraugh Mill. 18 of the total 23 records were collected in acoustic surveys at the Chasms with an impressive total of 485 recordings between November 7th and November 22nd. These were obtained at four different locations with some indication that there was more than one individual present. Recordings are a proxy for bat activity and not directly related to the number of bats present but nevertheless at one location there were over 100 recordings on one night and over 200 on another. On 14th November, Lesser horseshoe bats were recorded over a period of 5 hrs 17 minutes, although not continuously. There were also four occasions, on four different nights, when recordings were obtained almost simultaneously at two different locations 54 metres apart while on another night lesser horseshoe bats were detected at these and a further location, less than one minute apart.
Daubenton’s bat Myotis daubentonii
This species was especially targeted in 2024 with a stated aim of trying to identify roosts. Although the number of records collected increased to the highest total so far, 159 or 6% of the records for the year, only partial success was achieved. Acoustic surveys were conducted in the Laxey valley, from the washing floors to Snaefell mine, and in Glen Roy, but none of the 21 records indicated a maternity roost. However, 8 records on Snaefell and 7 in upper Glen Roy indicted probable hibernation sites, at Snaefell mine and at mine buildings in Glen Roy. From 1st to 4th October over 400 recordings were obtained at Snaefell mineshaft with a peak number of recordings 4 hours after sunset. The timings of the recordings are very suggestive of swarming behaviour while Myotis species of bats are now known to swarm in autumn at the same places that they hibernate.
Of the 36 acoustic surveys which recorded Daubenton’s bats, 8 were on farmland with nearby ponds, a further 8 were in riverine valleys, 4 in wetlands, 2 in woodland and 5 records were obtained during surveys designed to record lesser horseshoe bats in the south of the island. Finally, 6 records were obtained during roost checks of known or potential roosts of other species, including 3 at Silverdale. The most recordings in one night, 527, were obtained at Barnell Reservoir, not previously surveyed. The Bat Group participates in the National Bat Monitoring Programme, organised by the Bat Conservation Trust, including the Waterways Survey specifically designed to record Daubenton’s bats. It was again recording during this year’s survey on the lower Neb but not on the middle course of the river, nor on the lower Lhen trench although it was recorded during a static acoustic survey at Lhen Bridge earlier in the year.
Natterer’s bat Myotis nattereri
8 records of Natterer’s bats were collected during surveys for planning purposes, concerning one application, with the remaining 168 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 in May and November and resulted in 42 records, with most recordings obtained in November. The presence of this species at this location during this month indicates a hibernation site but evidence for hibernation, swarming, as for the Daubenton’s bats discussed above, was also found at Snaefell mine and upper Glen Roy where 9 and 20 records were collected respectfully. Although the actual number of recordings for this species was much less than for the Daubenton’s bats, Natterer’s bats are known to have a much quieter call and have to pass the detector within ca 5 metres to generate a recording. The number of recordings again peaked 4 to 5 hours after sunset.
Records from acoustic surveys were similar to those for Daubenton’s bats with the addition of Sulby hydroelectric station where the most recordings in one night, 125, were obtained.
Whiskered bat Myotis mystacinus
There were 186 records of Whiskered bat, 7% of the total, only marginally more than either of the two previously discussed Myotis species. In addition to all the surveys mentioned for those species it was also recorded around Rhendhoo Farm, Jurby East and in a garden at Jurby East, at Port Lewaigue and at the Children’s Centre at Walberry. Most records involve relatively few recordings, less than 20, whilst the greatest activity occurred around Kentraugh, with 200 to 400 recordings per night.
Brown long-eared bat Plecotus auritus
Although another quiet species there are a similar number of records for it than the Myotis species discussed above, 171, or 7% of the total. 13 of the records are from roosts, either actual counts or observations of bats emerging from a roost (8), or one or two individuals taking shelter (3). 2 records were of droppings identified by DNA analysis. Only 1 record was obtained during surveys conducted for planning purposes. Long-eared bats were recorded during most of the acoustic surveys already mentioned including the upland sites of Creg y Cowin, Snaefell mines and upper Glen Roy. The most recordings in one night were obtained at Snaefell mines, 67 and 88, on 3rd and 4th October respectively. In-hand specimens were recorded from Bishopscourt, and Greenlands Avenue and Rheast Mooar Avenue in Ramsey but all had to be put down at the vets. At least two were cat casualties.
Leisler’s bat Nyctalus leisleri
15% 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. Nevertheless, the number of records is down slightly this year in both numerical and percentage terms, with only 378 records. Only a few roosts are known and records were obtained from only three NBMP roost counts, two on the edge of Douglas and at a newly discovered roost near Sandygate. Recordings and observations at a property in Santon suggest another new roost. It was recorded during 8 planning surveys with one of them providing 52 records. This was adjacent to the roost near Sandygate. Records were obtained from acoustic surveys at 8 nature reserves (including the Chasms). It was also recorded hidden in horse blanket at a northern stables in October, at the Bungalow on the mountain in June and at Snaefell mine and upper Glen Roy in October.
Nathusius pipistrelle Pipistrellus nathusii
First recorded in 2018, there were rather fewer records this year than last, only 12. It was nevertheless recorded in every month from April to October and from Rushen to Bride. 9 of those records were of a single recording and the most recordings per night, 8, were from Silverdale with 7 recordings obtained at Lhen bridge. 5 records were obtained around Kentraugh.
Soprano pipistrelle Pipistrellus pipistrellus
With 199 records, 8% of the total, this is another species that has exhibited a slight decline on previous years. Two records are from the NBMP roost count at the same roost in the north of the island while a further two are from a new roost, probably males given that only one and two bats were seen. 5 records were incidental to roost counts for other species. 57 records were collected during 5 surveys for planning purposes. Acoustic surveys at 7 nature reserves, including the Chasms produced 33 records. As well as the nature reserve and planning surveys Soprano pipistrelles were recorded during transects along the Neb and Lhen and around Earystane and Kentraugh. The most recordings in one night, 226, were by the Rhendhoo Road in Jurby, while Jurby parish had the most records, 102, of any parish. The northern parishes had three times as many records as the south, 150 vs 49 confirming earlier observations that soprano pipistrelles are most frequently encountered on the northern side of the hills.
Common pipistrelle Pipistrellus pipistrellus
There are 770 records of Common pipistrelle constituting 31% of all records for the year. This species was recorded in every month, apart from January and December and in every parish and urban centre. Counts were conducted at 7 maternity roosts for the NBMP with the highest count of 146 bats at a property in Maughold. 9 records were obtained at new roosts including one in a bat box installed some years ago at Sulby Waterworks and six records from 3 new roosts at private properties. A further putative roost was confirmed in rather sad circumstances when some 45 dead bats, mostly juveniles, were found trapped inside an empty property in the north of the Island. 3 records were of individuals roosting at 2 properties surveyed for planning purposes. 3 specimens were brought to the attention of the bat care team via the Bat Helpline (tel 366177). 1 was released on site, 1 placed in a bat box on site and 1 did not survive. Sites surveyed include all those mentioned above but notable records, involving over 500 recordings per night, include Rhandhoo Farm, Jurby (on 3 nights), the Manx Birdlife nature reserve at the Point of Ayre (1 night), Barnell reservoir (2 nights), the footpath from Kentraugh to Colby (1 night), a private house on Summerhill Road, Jurby (2 nights), a wooded small-holding in Jurby (2 nights), Lhen bridge and an adjacent private property (1 and 2 nights respectively) and an estate in Santon. Of the 374 records around Kentraugh, 15 involve more than 750 recordings per night while the maximum was 1528 recordings per night.243 of the records involved social calls, either inter- or intra-specific antagonistic calls, mother-young contacts calls or male display calls. During a fairly late acoustic survey at Walberry, from September 17 to 19, there were a large number of social calls over the three nights, 528, almost as many as ordinary calls, 582. This suggests that the social calls were advertisement calls which males make to define their mating territory during the mating season. Follow-up surveys will have to be carried out in 2025 to attempt to identify the roost.
With thanks to all 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.