Northern Ireland's Priority Species

Pipistrellus pygmaeus – soprano pipistrelle

Pipistrellus pygmaeus

Pipistrellus pygmaeus (Leach, 1825)
Family: Vespertilionidae

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

It is not known how this species came to Ireland but it was first recorded in nineteenth century. In 1977 research revealed that the species known as the common pipistrelle actually comprised two closely related species. The differences lay in their DNA and, more obviously, in the frequency of their echolocation calls. So now the pipistrelle that calls at 45kHz is known as Pipistrellus pipistrellus, while the ‘other’ pipistrelle species is P.pygmaeus echolocating at 55kHz.

In brief

  • Found throughout Northern Ireland, in both rural and urban areas, and widely in England, Scotland and Wales
  • They roost in a variety of places such as trees, behind barge boards, soffits, cladding, under slates, etc.
  • Most common and smallest of our bat species weighing in at only 3 to 6gm.
  • Fur is mid to dark brown with dark face and membranes
  • Listed as a UK Priority Species
  • A 70% decline in numbers was recorded between 1978 and 1993 partly due to changes in agricultural practices and the increased use of roof timber treatment
  • They emerge just before dusk to feed on 3,000 to 3,500 insects a night, taking a variety that includes midges, mosquitoes, small moths, etc.
  • Nowadays the main threat to their survival probably comes from their exclusion from domestic roosts.

Species description
The common pipistrelle is the smallest of our bat species weighing in at only 3 to 6gm. Its fur is generally mid to dark brown while the face is usually dark brown, with short, broad ears. It measures 35–45mm from nose to tail and the wingspan ranges from 180 to 240mm. Juveniles have a greyer appearance than the adults.

Flight is rather twisting and erratic and at just above head height (about 3m high). They emerge at dusk to feed on 3,000 to 3,500 insects a night that they find along woodland edges, in open woodland, suburban gardens, marshes and over water. A variety of insects are taken, including small moths, midges, mosquitoes and lacewings.

During the summer, pipistrelle bats tend to set up their nursery roosts in confined spaces such as under slates or tiles, behind cladding, barge boards, soffits, window sashes, etc. Bat boxes are used occasionally especially in winter.

Life cycle
Pipistrelles are active from the latter part of March to late October/ November. Mating generally takes place in autumn at mating roosts, just before hibernation which lasts for four to five months. Where they hibernate is not known. Occasionally one or two bats are disturbed in cavity walls when building alterations are being carried out in winter. Maternity roosts are formed by the females from May onwards and a single baby is usually produced between June and mid-July. This baby feeds solely on its motherís milk for about six weeks at which stage it starts to forage for itself and becomes totally independent. It is not known for how long pipistrelles live but given their small size, they live a relatively long time, perhaps up to 15 years or more.

Similar species
Soprano pipistrelle and Nathusiusí pipistrelle

How to see this species
Pipistrelles leave their roosts just before dusk and can be seen searching for insects above hedges and around trees Like all bats, they follow flight-lines, for example, hedgerows and tree-line, to reach their feeding areas. They do not like flying in open exposed areas as this leaves them vulnerable to predation. They also feed along water edges, woodland edges, gardens etc. They can be detected using a bat detector tuned in to around 45kHz (common pipistrelle) or 55kHz (soprano/pygmaeus pipistrelle).

Current status
A 70% decline in numbers was recorded between 1978 and 1993. To date, it has been recorded in more than 800 sites and is our most commonly found bat, so, the pipistrelle population seems to have stabilised since the introduction of The Wildlife (NI) Order in 1985. In general terms, this legislation gives bats and their roosts full protection against deliberate damage or disturbance. They are also protected under the Conservation (Natural Habitats etc.) Regulations (NI) 1995. It is also listed as a species requiring strict protection in Annex IV of the Habitats Directive (1992) and Appendix III of the Bern Convention (1979). It is thought to be at the extreme north-western limit of its range and is considered to be a vulnerable species in the European context.

The actual number of roosts is likelt to be smaller as some of them have, until relatively recently, probably been misidentified Nathusiusí pipistrelle roosts.

Why is this species a priority in Northern Ireland?

  • Listed as UK Priority Species.

The species is listed in the Irish Red Data Book (1993) as being internationally important.

Threats/Causes of decline
In the past, this was probably partly due to changes in agricultural practices that have reduced the availability of insect prey and the increased use of timber treatment chemical by householders. Nowadays the main threat to their survival probably comes from their exclusion from domestic roosts.

They are also vulnerable to disturbance and roost loss for other reasons including building renovations and roof repairs to domestic dwellings.

Conservation of this species

Current action
There is a UK species action plan for Pipistrellus pipistrellus which was published in 1995.

  • The Northern Ireland Bat Group collates records for this species
  • Implementation of the Northern Ireland Habitat Action Plan for Species Rich Hedgerows and the Woodland Habitat Action Plans.

Proposed objectives/actions

  • Maintain the existing population size of Pipistrellus pipistrellus
  • Maintain the existing geographical range of Pipistrellus pipistrellus
  • Maintain the existing population size of Pipistrellus pygmaeus
  • Maintain the existing geographical range of Pipistrellus pygmaeus
  • Restore population size of Pipistrellus pipistrellus to pre-1970 numbers
  • Restore population size of Pipistrellus pygmaeus to pre-1970 numbers.

What you can do
Be more tolerant of bats should they roost 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. Tel: 028 9039 5264, [at]

Further information

UK Species Action Plan Pipistrellus pipistrellus

Northern Ireland Bat Group

Bat Conservation Trust

The Wildlife (Northern Ireland) Order 1985

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 Naturalistsí Journal (2000). Special Zoological Supplement.

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

iNaturalist: Species account : iNaturalist World Species Observations database