News | Latest News | Greater horseshoe bat arrives in Ireland

The text received on my work mobile phone on Sunday 24 February was short and sweet:

‘Guess where I found a hibernating lesser horseshoe today’?

The message was from bat consultant Paul Scott and the duplication of question marks was well justified because it referred to his discovery of the bat during a survey of old buildings in County Wexford. Those familiar with the distribution of the lesser horseshoe bat in Ireland (check elsewhere on our website for information on this species ) will know that it is confined to the six western counties of Mayo, Galway, Clare, Limerick, Cork and Kerry, so finding one so far outside its known distribution range was unexpected, to say the least. Speaking to Paul the following day, he told me that while he was sure it was a horseshoe bat, the height at which the bat was hanging made it difficult to say for certain that it was indeed a lesser horseshoe bat. Our nearest neighbours, England and Wales, have two species, the lesser and greater.

There are five species of horseshoe bat (Genus Rhinolophus) in Europe, all easily spotted at a distance by their habit of always hanging free in their roost, wholly or partially wrapped in their wing membranes. However, distinguishing between the species requires close examination of their faces, in particular the elaborate nose leaf, which is made up of a horseshoe-shaped flap of skin surrounding the nostrils, a protrusion above the nostrils shaped like a hatchet (sella) and a triangular section (lancet) at the top of the nose leaf. The lesser horseshoe is the smallest European horseshoe bat and one of my identification books states that it cannot be confused with other species because of its small size (plum-sized) and rounded upper section of the sella. But this nugget of information is not very helpful when the bat is hanging several metres above your head in the dark.

Thankfully Paul was able to collect some droppings that he sent to the Centre for Irish Bat Research (CIBR) in University College Dublin for DNA analysis to definitively determine the bat’s identity. In the interim, Paul and two other (licensed) bat experts revisited the cellar to find that the bat had moved to a spot that enabled them to make an estimate on size and to actually catch the animal for close inspection. After careful consideration, all were in agreement that the bat was indeed a male greater horseshoe bat (Rhinolophus ferrumequinum), with a forearm length of 55.6mm and weighing 19.6g. A lesser horseshoe’s forearm is 37mm and the weight range is 4-9.4g. Another excited phone call from Paul!

We were now looking at a new species of bat for Ireland, rather than a resident one exploring new territory. Now theories are being discussed as to why this animal is here. Although we have no way of establishing when it arrived, it may not be a coincidence that we have just experienced an unusually long period of easterly winds, so the greater horseshoe bat may have been blown over here from its original roosting site in south and west Wales or south and west England. The population of the greater horseshoe bat in Britain underwent a dramatic decline during the 20th century, as it did throughout its European range, but thanks to targetted conservation measures it is now recovering.

Bat workers in Britain occasionally record this species some distance from its usual distribution range, but crossing the Irish Sea is a first for this species.

Or is it?

A male and female greater horseshoe bat were ‘introduced’ into a dark passage under Castle Leslie, Glaslough, County Monaghan by a young boy called John Leslie in August 1929. He took the time to let the scientific community know this by sending these details to The Irish Naturalists’ Journal and the article was published the following year. At the time John Leslie (now Sir John Leslie) was a pupil at Downside School, Stratton-on-the-Fosse, near Bath and he thought it would be a good idea to have greater horseshoe bats at the castle (he regularly watched colonies of both greater and lesser horseshoe bats in Wells Cathedral). I had the pleasure of meeting Sir John in 2004 at Castle Leslie and we talked about his lifelong interest in bats. He told me how he had been firmly rebuked at the time for taking the bats from England, which he felt was unfair, as he was only a boy. I formed the impression that he was still quite annoyed at this!

The Mammals of the British Isles Handbook states that the greater horseshoe bat is limited to the south west of Wales and England due to the milder climate in these areas. Severe winters affect the survival of the young bats (pups) and cold springs delay the timing of births and the growth of the pups. I grew up in County Monaghan and can vouch for the early arrival of autumn frosts and extended duration of cold springs. There is no possibility that the Wexford greater horseshoe is a descendant of the Castle Leslie pair, purely on the basis of climate.

In order to track where this bat may go in the future, a special ring has been placed on its forearm (between the wrist and elbow) that will be easily visible if it is spotted elsewhere. This is not the first time that bats have been ringed in Ireland, but to mark this amazing discovery a ring bearing the following notation was used: IRL0001. A tiny section of wing membrane was collected on the day it was ringed and dispatched to CIBR for DNA analysis: this may reveal the bat’s country of origin as bats living in different geographic areas can reflect this in their genetic makeup.