Northern Ireland's Priority Species

Plecotus auritus – brown long-eared bat

 
Plecotus auritus
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Plecotus auritus (L., 1758)
Family: Vespertilionidae

Bats are the only true flying mammals and here in Northern Ireland there are eight species of them. All our bats only eat insects. Although they are not blind, they use echolocation to build up a ‘sound’ picture of their environment and prey. Historically, they would seem to have been quite common.

In brief

  • Small bat (6-12g) with exceptionally long ears which are nearly as long as its body
  • Northern Ireland’s third most commonly recorded species with just over 200 records derived from just under 150 sites throughout Northern Ireland
  • Very agile fliers that can manage easily in the confines of woodland canopies
  • Low numbers of animals form roosts in the open roof spaces of older buildings such as ‘stately’ homes, or in churches
  • Roosts are usually found in the open roof spaces of older buildings where they prefer to hang up along the central ridge beam
  • Bats as a group are considered to have declined
  • Like all of the bat species, they are affected by loss of roost sites.

Species description
As its name suggests, the brown long-eared bat has exceptionally long ears measuring from 10 to 14mm – nearly as long as its body. They are smallish bats ranging in weight from 6 to 12g. When at rest, the ears are often not obvious as they can be tucked away under a wing or curled back like ram's horns, with just the long, pointed inner lobe (tragus) visible. The relatively short broad wings allow for slow, quiet flight and great agility, especially in confined spaces. Because they are such quiet fliers, brown long-eared bats are also known as whispering bats.

The long fluffy fur is grey-brown in colour, with lighter grey fur on the belly. Juveniles appear pale grey in colour as they do not have the brown tinge of the adult.

Hunting begins about an hour after sunset and occurs in woodland, near thick vegetation, parks, gardens, etc. Their prey is made up of a variety of insects including moths, flies, which they catch on the wing. They also feed on non-flying invertebrates, such as spiders, beetles and earwigs which they catch by gleaning, where the bat detects and picks resting insects from off foliage. Larger insects, such as moths, are taken to a feeding ‘perch’ beneath which can be found discarded insect remains, especially wings.

Life cycle
Mating takes place in the autumn, but fertilisation is delayed until the following spring. In April and May maternity roosts of 10 to 20 or 30 females are formed. Unlike many species of bats, male brown long-eareds can also be found in these maternity roosts. The female gives birth to a single baby (rarely two) sometime from mid-June to mid-July. Up until the baby is six weeks old it is fed on its mother’s milk. By three weeks old the young bats are flying within the roost in preparation for being totally independent in a further three to four weeks. Most female long-eareds do not breed until their second year and they do not necessarily breed every year after that. Males, on the other hand, are sexually mature after about 15 months but may not breed until they are two years old. Summer roosts and maternity roosts are found in the open roof spaces of older buildings such as ‘stately’ homes, or in churches. They prefer to roost along the central ridge beam of these airy roof voids. So far, there is only one record for a hibernation site in Northern Ireland and that is of a single bat in a cave in County Fermanagh. However, in England, small numbers have been found tucked away in caves, tunnels, ice-houses etc. Depending on the weather and availability of insects, Brown long-eared bats will hibernate from about mid-November to March or early April.

Similar species
Grey long-eared bat – never yet been recorded in Northern Ireland.

How to see this species
They occur throughout Northern Ireland in older buildings and woodlands. They emerge abut an hour after sunset. Although they echolocate at around 35/40kHz, their calls are so quiet that it is difficult to get them to register on a bat detector.

Current status
Brown long-eared bats are common throughout Northern Ireland, and it is our third most commonly recorded species with just over 200 records to-date. Even so, as roost sizes are quite small and many of the records are of single bats, the overall number of individuals is not high. Historically the picture would seem to be rather different with brown long-eared bats reported to be ‘met with everywhere’ in late nineteenth-century County Down (Knox, 1875).

Brown long-eared bats (and their roosts) are fully protected under the Wildlife Order (Northern Ireland) Order 1985 and under the Conservation (Natural Habitats etc) Regulations (NI) 1995.

Why is this species a priority in Northern Ireland?

  • Bats as a group are considered to have declined.

The brown long-eared bat is listed in the Irish Red Data Book (1993) as being internationally important. Given that the roost sizes are fairly small (less than 50 animals) the overall number of BLE bats present in Northern Ireland is possibly as low as a few thousand, leaving them vulnerable as a species.

It is also listed as a species requiring strict protection in Annex IV of the Habitats Directive and Appendix II of the Bern Convention (1979).

Threats/Causes of decline
Like all of the bat species, they are affected by loss of roost sites. For example, potential or actual roosts, such as hollow trees, are often felled because they are considered unsafe or just ‘untidy’. Habitat change and loss have a detrimental effect on bats by altering (usually reducing) the availability of their prey. The removal of hedgerows (flight ‘corridors’) makes it difficult for bats to reach their feeding areas as they do not like flying over open ground. The increased use of pesticides has resulted in severe declines in the abundance of insect prey. They are very vulnerable to the effects of water pollution and to chemicals used in timber treatment.

Brown long-eared bats occasionally forage or land on the ground and this leaves them open to predation, especially by domestic cats.

Conservation of this species

Current action

  • The Northern Ireland Bat Group collates records for this species
  • Implementation of the Northern Ireland Woodland Habitat Action Plans.

Proposed objectives/actions

  • Maintain the current range.

What you can do

  • Cultivate plants that attract insects
  • Leave trees that have holes but are otherwise safe
  • Be more tolerant of bats should they roost in buildings, especially outbuildings, on your property
  • Monitor sites and population sizes and send in records to the Northern Ireland Bat Group, c/o National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU.

Further information

Links
Northern Ireland Bat Group

Bat Conservation Trust

Northern Ireland Habitat Action Plans

Northern Ireland's Mammals, Amphibians & Reptiles

The Wildlife (Northern Ireland) ) Order 1985.

Literature
Stebbings, RS and Jeffries, DJ. Focus on Bats. (2004). (Adapted for N Ireland and published by Environment & Heritage Service).

Hayden, T and Harrington, R. (2000). Exploring Irish Mammals. Town House and Country House Ltd, Dublin, Eire.

Allen, P, Forsyth, I, Hale, P, and Rogers, S. Irish Naturalists’ Journal (2000). Special Zoological Supplement.

UK Biodiversity Action Plan.

Text written by:
Lynne Rendle, CEDaR Vertebrate Officer, Ulster Museum