Echolocation
To distinguish them from common pipistrelles they are often referred to as ‘55s’. Although social calls and chatter in the roost are audible, their echolocation calls are ultrasonic. On a bat detector they can be heard as a series of clicks and slaps, similar to those of the common pipistrelle, but are loudest at around 55 kHz on average. Pipistrelles with peak frequency above 52 kHz are classified as soprano pipistrelle.
Habits
Whilst the common pipistrelle is a generalist found in a wide range of habitats, soprano pipistrelles are more specialist. They usually forage in or near wetland habitats, over lakes and rivers, and also along woodland edges and tree lines. They feed mainly on flies, particularly the midges and mosquitoes associated with water.
Summer roosts of females are in tree holes, or in tight spaces on the outside of our houses, including modern ones. Single or small numbers of bats are found only occasionally in winter, in crevices in buildings and trees. Studies show winter activity around buildings, bridges, tree cavities. They are rarely found underground.
Reproduction and life cycle
Popular spots for maternity roosts are under hanging tiles and weather boarding, behind barge boards, between roof felt and tiles or in cavity walls. They exhibit strong roost fidelity, often returning to the same area each year. However, newer studies indicate that individuals frequently switch among multiple roosts within a season. Summer roosts are typically larger than those of the common pipistrelles. Their audible chattering can often be heard just before they emerge, about 15 minutes after sunset, and it can be exciting to watch them return at dawn, though householders may be unaware of their presence. The young are fed solely on mothers’ milk for three to four weeks. After about four weeks the young start to fly and at six weeks they are able to forage for themselves. Once the young are foraging the maternity roosts start to break up. Males usually roost singly or in small groups. In late summer and early autumn they defend mating roosts to which they attract females by making ‘song flights’ and social calls.
Distribution, status and conservation
The soprano pipistrelle is widely distributed across the UK, but populations have declined in recent decades. Very large summer roosts were not unusual 50 years ago: several of around 1,000 were recorded by the KBG in the early 1980s, but more recent records show more dispersed, smaller roosts. Although national monitoring suggests that numbers have remained steady over the last 15 years, the average size of maternity roosts in Kent appears to be much smaller than in the past. NBMP 2024 shows long-term increase and stable short-term trend.
The map reveals that most of the known maternity sites are close to rivers.
In addition to making gardens more bat-friendly, as described for the common pipistrelle, their habitat can be improved by providing a network of new patches of woodland. These can be quite small, but should be no more than about 500 m apart and connected by hedges. Some taller trees should also be allowed to grow in hedges.
