A summary of bat records for 2022
During the year many more surveys were carried out than in the previous year, with several bat group volunteers deploying bat detectors for varying time periods, notably in the south, a previously grievously under-recorded area. A visiting UK bat worker also conducted a four night static detector survey at eleven sites in the south, adding considerably to our knowledge of bat distribution. A total of 255 surveys were undertaken, lasting from one or two hours in the case of transects to ten or more nights but most commonly for 3 to 4 nights. Individual bat records have yet to be extracted from most of these, a bat record being one species in one location on one date. 575 records have so far been entered on the database.
Vespertillionidae
Records are assigned to family level where the observer is unsure what species is being observed, or otherwise fails to record it. 16 records of unidentified bats were collected from all around the Island while nearly half of all the bats assisted by the Bat Helpline (tel 366177) fall into this category. 3 of these were casualties of cat predation.
Myotis species
Recordings of Myotis bats that could not be identified to species level occurred on a third of all surveys but in 90% of cases other identifiable Myotis calls were present giving a clue as to which species was present.
Pipistrellus species
Bats are usually assigned to this category when recordings of social calls are made. Identifying social calls to species level is a fine art and not usually attempted. It is notable that out of the 68 surveys with recordings of social calls, there are 11 with more than 100 recordings all bar one of which occurred in August or afterwards, after the young of the year would have been on the wing.
Lesser horseshoe bats Rhinolophus hipposideros
Some effort was again made in 2022 to locate lesser horseshoe bats and it was recorded on four occasions, all in Rushen parish, twice at coastal sites and twice along the lower Colby River.
Nathusius pipistrelle Pipistrellus nathusii
This is another recent immigrant which the Bat Group is keen to locate and more records were obtained in 2022 than the previous year. 19 surveys detected the presence of this species, all bar one in the south with the outlier being Sandygate. The southern records are largely from the lower Colby River area although it was also detected at Fisher’s Hill and Chapel Hill, Cronk Thatcher in Colby, Port Grenaugh and Ballacallin in Patrick.
Daubenton’s bat Myotis daubentonii
The Bat Group Does not know of any maternity roosts for the next species, Daubenton’s bat, but did put in some extra survey effort in 2022, taking part in the UK Bat Conservation Trust’s Waterways Survey for the first time. It is hoped that this will become a regular part of the Bat Group’s efforts to monitor bats on the Island. Often erroneously called the water bat because of its association with still waters, Daubenton’s bats can be recorded well away from water in woodland or along hedgerows. A visiting UK bat worker recorded them at Chapel Hill, Rushen and two sites on the slopes up from Colby while a Bat Group volunteer recorded them at two sites in the Ballakilpheric area. There were recordings during 20% of the surveys undertaken in 2022 with other atypical records from my garden in Jurby East and the beach at the Lhen. They were detected at the Chasms in late March and mid-May. The largest number of recordings were obtained at Rosehill ASSI followed by Glen Dhoo nature reserve with more typical sites being Silverdale boating lake and the rivers Neb, south of Peel, and Silverburn, north of Castletown. Individual bats were caught and released (under licence) in a harp trap by visiting UK bat workers at the two former locations during a week-long trapping survey in July.
Natterer’s bat Myotis nattereri
A maternity roost of Natterer’s bats was discovered in a disused barn in Jurby parish but none of the other half-dozen known sites for them were checked during the year. Away from the Jurby roost the most recordings were actually at the Chasms at the end of March while Rosehill ASSI was the only other site to have more than 100 recordings during a survey. It is rare to reach even double figures for recordings of this quiet bat during surveys and the only other sites to do so were Glen Dhoo nature reserve, the beach at the Lhen, a garey in Ballakilpheric and a private house in Jurby. Other notable locations where they were recorded include Glen Dhoo nature reserve, where a long-term survey was conducted, the brooghs above Bulgham Bay and sites overlooking Colby. Three individuals, all males, were harp-trapped at Port Soderick and Colby Glen along with a female at the Curraghs Wildlife Park.
Brown long-eared bat Plecotus auritus
Apart from the survey results, some interesting records were collected for the brown long-eared bat. Two new maternity roosts were discovered while numbers of individuals roosting at a hall in Sulby were the most ever recorded, 33, in our long-term monitoring programme. Several individuals were also found, in early Spring, huddled together in a bat box recently erected in Glen Helen while in October a small cluster of them were found inside a door frame at a house on an estate in Port Erin. This species occurred on 82 of the surveys, or 32%, with usually less than 10 recordings during any one survey for this notably quiet bat. It was recorded at Glen Dhoo nature reserve each month during the long-term survey and during several surveys conducted on farms in the north of the Island. Coastal records include Perwick Bay and Port Grenaugh while other sites in the south included six sites above Colby along with Billown Wood wildlife site. Finally, six individuals were trapped and released at Port Soderick, The Raggatt and Close Sartfield nature reserve.
Whiskered bats Myotis mystacinus
Four whiskered bats, 1 male and 3 females, were trapped at Port Soderick, Close Sartfield and Silverdale Glen while overall the species was present during 108 of the detector surveys, about the same as in 2021. However, because more surveys were conducted in 2022 this represents a decrease in their presence in percentage terms, from 61% to 42% so there must have been more surveys in 2022 where whiskered bats were not detected than in 2021 and the reason for this has still to be investigated. Coastal records included Cronk y Bing nature reserve, Blue Point and Perwick Bay together with the Chasms in February, March and May. There was much activity at Glen Dhoo throughout the long term survey there and also at Ramsey Woods MWT reserve and Billown Wood wildlife site. One maternity roost was counted with 14 individuals emerging.
Soprano pipistrelles Pipistrellus pipistrellus
A survey for planning purposes disclosed a, probably abandoned, maternity roost of at a property near the Claddaghs, Sulby while a further two roosts were counted, one of which had over a hundred bats and the other over 200. Two surveys in the north of the Island recorded over 2000 calls of soprano pipistrelles. Three MWT reserves surveyed produced a total number of recordings in excess of 100, these being Ramsey Woods, Goshen and Glen Dhoo while only one occurred in the south, at Silverdale Glen. It has been said before that the south of the Island seems to have few soprano pipistrelles inhabiting it and, indeed only 4 surveys with the number of recordings between 10 and 100 took place there, at Poulsom Park, Silverdale and a transect from the Chasms to Pt St Mary. There were 10 such surveys in the north, including my garden in Jurby East, several northern farms and three northern beaches; Blue Point (in both June and September), the Lhen in June and Cronk y Bing in September. This pattern was repeated during the trapping week in July conducted by UK bat workers in which 6 bats were caught at Close Sartfield, 4 at the Curraghs Wildlife Park , one at the Raggatt and 5 at Silverdale Glen. The leader of the UK bat workers, Rachel Bates, also conducted static surveys over four nights at 11 sites in the south but only had soprano pipistrelle calls, fewer than 10, at 4 sites, Colby South and North, Ballakilpheric and Ballacallin, Patrick.
Leisler’s bats Nyctalus leisleri
Leisler’s bat is relatively common and is detected in surveys all over the Island, from the Chasms to Blue Point and from sea level to Stoney Mountain. 75% of all surveys recorded Leisler’s bats and even for those surveys where they were apparently absent there were adjacent sites which did record them. Nevertheless, few roosts are known for this species and only one count was made with only 2 individuals emerging whereas previous counts have revealed 80 – 90 bats. It is hoped that this is just an example of roost switching and that the bats were present in an alternative site, perhaps to return next year. Common pipistrelles (Pipistrellus pipistrellus) also exhibit such roost switching behaviour, sometimes only every few days. Leisler’s bats are strong, high fliers with loud calls picked up by detectors at much greater distance than other species so it can be problematic to tie recordings to habitat. One intriguing record was obtained thanks to Rachel Bates who submitted a dropping from a Leisler’s bat for DNA analysis which revealed that it had been feeding on nocturnal dung beetles. That bat was one of four caught during the trapping week, one at Colby Glen and three at Port Soderick. Rachel also recorded many calls that could not be assigned to either of the two British Noctula species (N. leisleri and N. noctula) which is usually done on the characteristic frequency of the end of the call, N. noctula being lower than N. leisleri. There were over 1800 such calls at 10 of her 11 sites, with over 1500 calls at one site alone, Chapel Hill. In addition she recorded 53 calls, at 7 sites, which were low enough in frequency to be classified as N. noctula, the noctule, a species not known to be present on the Island. However, it is known that some bats lower their characteristic frequency in the absence of their conspecifics so without further evidence of the presence of noctules these calls are being regarded as from Nyctalus species. Two Leisler’s bats were taken into care, one from a known roost site was later released but the other, from Peel, died shortly after collection, suspected of having been in collision with a vehicle.
Common pipistrelle Pipistrellus pipistrellus
The Common pipistrelle truly lives up to its name, being recorded during 97% of all surveys and it was only absent from winter surveys at the Chasms in January and March. The average number of recordings per survey, with durations varying from two hours to two or more weeks is 294, while at favoured sites it is not unknown for the number of recordings to exceed 1000 per night. Common pipistrelles were recorded at coastal sites such as Perwick Bay and the northern beaches from the Lhen to Rue Point, in woodland, grassland, forestry plantations, riversides and disturbed ground and from sea level to 350 metres altitude. 17 of the 48 calls to the Bat Helpline involving bats were of this species, 7 of which were cat casualties. Nevertheless seven at least were released including one female which gave birth while in care. 15 roosts were counted as part of the Bat Conservation Trust’s monitoring programme, with counts of bats emerging varying from 1 to 201.8 new roosts were discovered half of which are subject to re-roofing or other planning development and so may or may not survive. Two roosts were re-discovered, re-occupied after a period of absence, at one of which a mother and baby were regrettably found dead but remarkably the adult had been ringed in 2019 a mile or so distant. This represents the Bat Group’s first ringing recovery.
Thanks must go to all who submitted bat records and assisted in the surveys, in particular Rachel Bates and her colleagues from the UK.