Common pipistrelle Pipistrellus pipistrellus

Common pipistrelle - click to enlargeAs its name suggests, the common pipistrelle is the most common bat in Northern Ireland. It was only recently discovered that the bat we though was the common pipistrelle was actually two species, now called the common pipistrelle and the soprano pipistrelle. It is a small species and has dark brown fur which is slightly paler on the underside. Common pipstrelles emerge to forage just after sunset and are found in a variety of habitats, often foraging along tree lines and hedgerows on farmland. They are found roosting in quite large numbers in houses and tree holes. In winter, the common pipistrelle hibernates.

SPECIES DESCRIPTION: The common pipistrelle is generally reddish brown to dark brown, but lighter on the undersides. The membranes, ear and face are usually very dark brown, but not as dark as Nathusius' pipistrelle. In comparison to the soprano pipistrelle, the face of the common pipistrelle is generally darker, often with a dark band across the face and eyes. As it a result it is sometimes known as the 'bandit' pipistrelle. However, this feature is not always present and there is some overlap with the soprano pipistrelle. The ears are short and broad and the tragus is short, parallel-sided and terminates in a blunt tip. A small lobe (postcalcarial lobe) is present on the calcar of the tail membrane which separates the pipistrelle and Leisler's bats from all other species in Northern Ireland. Head and body length is about 35-45mm and the forearm is about 28-35mm. The weight of adults can vary from 3.7 to 5.8g. Common pipistrelles emerge early, occasionally before sunset and their flight is rapid and agile at about 5-10 m above ground. Common pipistrelles roost in building and tree holes. In comparison with the soprano pipistrelle, bats tend to roost in smaller numbers, up to about 50 individuals and are commonly encountered in modern buildings, roosting under slates, in cracks in walls, and under soffit and barge boards. Females form large maternity colonies during May and give birth to young during late June and July. Young are weaned and able to fly at around 3-4 weeks. Males are solitary during this time and establish mating territories during August. The mating period extends to October and male bats are particularly vocal at this time producing many social calls to attract a mate. Males form harems during this time. Fertilisation is delayed and hibernation occurs from late October to late March and early April.

KEY IDENTIFICATION FEATURES:



© Jon Russ 2001. Text refereed by Angela Ross & Lynne Rendle.

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