Cornwall Mammal Group

One of the smallest British mammals, the pipistrelle is also our most common bat.
Weighing less than 7 g, and with a wing span of up to 260 mm, the dark brown fur of the back fades slightly to the belly. The
short ears have a short, rounded, tragus and there is a small area of tail membrane behind the heel spur which helps to 

discriminate pipistrelles from the other small British bats. Three pipistrelle species have been recorded in Cornwall and the common and soprano pipistrelles are virtually identical in appearance. The most reliable way of telling them apart is with a bat detector, indeed this was the first indication that the familiar pipistrelle was actually two closely related species; this was only confirmed by DNA analysis in the late 1990s. Common pipistrelles tend be slightly larger and darker than sopranos, and sopranos are more likely to have pinker faces.

 

Both species are often seen hunting with their fast, darting, flight early in the evening. Common pipistrelles forage over a range of habitats including woodland, gardens, grassland and lakes, whereas soprano pipistrelles hunt mainly near to water. Their echolocation calls are similar sweeps of frequency modulation but common pipistrelles’ calls are strongest at around 45 kHz, whilst those of the soprano peak at 55 kHz.

 

Nathusius’ pipistrelle is similar in appearance to the common and soprano pipistrelle,

although generally slightly larger and with longer and shaggier fur on its back. Bat
specialists can discriminate Nathusius’ pipistrelle from its close cousins through
detailed differences in the external reproductive organs and the relative size of the teeth. There are also differences in the patterns of veins in the wing, and in the
relative lengths of the forearm and the 5th digit. Experienced bat workers can also
separate the pipistrelle species by analysis of their echolocation and social calls. Nathusius’ pipistrelle uses calls of around 37 kHz, somewhat lower than the common (45 kHz), and soprano (55 kHz) pipistrelles.

The common and soprano pipistrelle species are very adaptable in selecting their summer

roosts and are the bat most likely to take up residence in modern houses. They will roost in the spaces between tiles and roofing felt, in the cavities of a wall, or behind plastic fascia boards. They rarely use the roof space but they can be found in bat boxes and tree cavities.

They mate in the autumn and the females (together with an occasional male) occupy maternity roosts of between a few dozen and several hundred individuals, soprano pipistrelles tending to roost in larger numbers. 

 

The different species use separate roosts, soprano pipistrelles often using the same site over several years, common pipistrelles being much less loyal. The single pup (or very occasionally twins) weighs less than 1 g and is suckled for up to 6 weeks. Pups make their first flights at 3 weeks and while their mother is feeding they huddle together in crèches. Males set up 

breeding territories in the autumn, often around a tree cavity, to which they attract females using a special “song-flight” call. Small groups of females may roost with the males at this time. Pipistrelles eat huge numbers of small flies and midges, catching them in mid-air using their tail or wing membrane. They may travel 3 or 4 km from their roost sites to forage.

Surprisingly, winter hibernation sites for pipistrelles are seldom identified; they are rarely found hibernating in caves and may use buildings or trees where they assemble in small groups. Pipistrelles are sometimes found hibernating in bat boxes. They usually hibernate between November and late March. Pipistrelles are vulnerable to roost disturbance, the adverse effects of wood treatments, and to loss of habitat and agricultural impacts on prey species.

 

Nathusius’ pipistrelle is found in woodland and parkland, but always near water, where they feed on midges and other small aquatic insects. The bat is not well studied in the UK and many aspects of its ecology and behaviour are similar to those of the related pipistrelle species. Male Nathusius’ pipistrelles occupy mating roosts during the autumn where they emit complex social calls; this contrasts with the common and soprano pipistrelles which produce their simpler calls whilst flying. In Europe Nathusius’ pipistrelles are known to migrate south-west in the autumn, returning to their breeding sites in eastern Europe in late spring. In the UK this
migratory behaviour is not well documented, but there are indications that some animals arrive from Scandinavia in the autumn.