by Dr Kate McAney, The Vincent Wildlife Trust
Ireland is currently home to nine species of bat. All our bats are totally harmless, much smaller than people imagine and very dependent on humans for their survival. All Irish bats eat insects; some prefer chunky beetles and moths while others, such as the pipistrelles, catch large numbers of small flies and midges. However, during winter when insects are scarce, Irish bats hibernate; they lower their body temperature and heart beat, which enables them to survive for periods without feeding.
Bats are mammals, but they are the only mammals capable of true flight. In Ireland, as throughout the rest of the world, they account for almost a quarter of all mammal species. They are a fascinating group of animals but much misunderstood. Bats are not blind! They can see perfectly well, but in order to hunt tiny midges in the dark and to avoid colliding into obstacles, they rely on their hearing. As well as producing sounds we can hear, such as squeaks, bats emit an amazing range of high-pitched sounds well beyond our hearing range. These sounds bounce off objects and return to the bat as echoes that the bat uses to judge size, distance and speed. This system of 'seeing with sound' is called echolocation or sonar and is so accurate there is no way a bat will accidentally fly into your hair!
Female bats form nursery colonies in summer in order to raise their young. A female bat gives birth just once a year to one baby, usually in June, which she suckles for about six weeks. Once the young are independent, the females move off to join male bats that have roosted singly or in small bachelor groups during the summer. Mating takes place in autumn. This is a busy time for the males, as they need to perform elaborate flights and emit special signals, often audible to humans, to attract females. Although mating occurs at this time, pregnancy is delayed until the following spring when food becomes plentiful again.
Bats in buildings
Bats live in a variety of places or 'roosts', both natural and man-made. However, they are becoming more dependent on buildings for roosting sites as their original roosts, such as trees, disappear. Bats move between roosts throughout the year, needing warm sites in summer for rearing the young and cold sites in winter for hibernation. However, they are faithful to their roosts and will continue to return every spring as long as conditions remain suitable. Contrary to the popular saying 'Bats in the Belfry', most bats like to live in roofs of occupied houses, which are warm and dry. Most of our bats fly up to a building, land and then crawl through a small opening. The small pipistrelle can get through gaps as small as 15mm x 20mm, and even our largest species, Leisler's, can enter through holes too small for sparrows or starlings. Bats do not make nests; they simply cling to the timber, felt or stonework of the building. Usually the first clue to the presence of bats in a house is their droppings. These are similar to mice droppings but consist of dry insect remains that crumble to a fine powder, while those of mice are smooth, sticky when fresh and hard when old.
Telling the species apart
The pipistrelle bats are the most commonly occurring bats in houses and the smallest, weighing only a few grams and measuring just 33-48mm long. There are in fact three species of pipistrelle in Ireland; best identified on the basis of the echolocation sounds they produce. They are easy to spot at dusk as they fly erratically when hunting along the edges of woodland and hedgerows, in gardens and beside water. The long-eared bat is easily recognised by its fabulous ears, which are almost as long as its body (37-52mm). It is usually possible to see this bat resting on timbers in the open space of a roof. It is also common in churches. In flight it is highly manoeuvrable and usually feeds very close to trees and bushes where it picks insects off the vegetation.
Leisler's bat is our largest species but still only measures 50-69mm in body length. It roosts in houses and although this bat is considered common in Ireland, it is rare throughout the rest of Europe, where it roosts primarily in trees. It is possible to identify this bat in flight as it flies out in the open, often quite high, at or soon after sunset. Its echolocation call sometimes falls within the range of human hearing.
The Lesser horseshoe is confined to the west of Ireland where it prefers unoccupied houses and outbuildings in summer and underground sites in winter. It gets its name from the horseshoe-shaped piece of skin surrounding the nostrils. This small bat always hangs down by its slender legs and when at rest, it wraps its wings tightly around its body.
The bat seen flying fast and close to the surface of countless lakes and rivers at night is the Daubenton's bat. It is often found roosting singly or in small groups under bridges.
The remaining two species, Natterer's and Whiskered, are not encountered as often as the other species but they also roost in buildings and hunt in woodland. Natterer's bat has a very pale underbelly and long ears while the Whiskered bat is quite a dark bat, with a black face and wing membrane.
Bats and the law
Populations of bats worldwide have been declining since the middle of the last century. The main reasons for this decline are the loss of both summer and winter roost sites through human disturbance, the destruction of woodland, the renovation of buildings, the use of toxic timber treatment chemicals, the clearance of hedgerows and use of agricultural insecticides. To try and conserve remaining populations, all Irish bats are protected under the 1976 Wildlife Act and also by The European Habitats Directive. It is an offence to intentionally kill, disturb, handle or keep bats without a licence. However, it is not an offence to look after an injured bat or a young bat that has been abandoned. Under The Habitats Directive, both the roosting sites of bats and their hunting habitats are protected.
What to do if you find bats in your attic
Don't panic! In the vast majority of cases, you need do nothing. However, if the bats are giving rise to concern, you need to liaise with Duchas or a bat group on ways to alleviate the situation. Never block up access holes in summer as this will have disastrous consequences for the mothers and young. Ring Duchas at 01- 6472300 and ask for the name and number of your local conservation ranger before doing anything that might disturb the bats, including repair work or timber treatment. Other groups offering assistance are:
Bat Conservation Group Dublin Tel: (01) 8347134
Cork County Bat Group Tel: (021) 7339247
Galway Bat Group Tel: (091) 794435
The Vincent Wildlife Trust Tel: (093) 35304 (primarily for queries on lesser horseshoe bats and bats in trees).
The Bats of Britain and Ireland by A.J. Mitchell-Jones. Illustrated by D.W. Ovenden. Published by the Vincent Wildlife Trust, 10 Lovat Lane, London EC3R 8DT.
This booklet is priced £3.00 Irish and is available from Kate McAney,The Vincent Wildlife Trust, Donaghpatrick, Headford, Co. Galway.