Leisler’s Noctule

Identification

Leisler's noctule is a medium-sized insectivorous bat, slightly smaller than the common noctule, with a head and body length of 48 to 68 mm and a wingspan of 260 to 330 mm. It weighs between 11 and 20 grams. The species is characterized by its dark face, ears, and wings, combined with brown fur that is notably darker at the base than at the tip—a useful distinction from the common noctule, whose fur is uniform in colour throughout. The undersides of its arms are distinctively hairy, earning it the alternative name "hairy-armed bat." Look for short, rounded ears with a distinctive mushroom-shaped tragus, and notably long, narrow wings that give the bat its swift, agile flight profile.

Range & Habitat

This species is found locally across Europe and western Asia, ranging eastwards to the Urals and Himalayas, and also occurs in north-west Africa, the Canary Islands, and Madeira. The bat typically inhabits forests—both coniferous and deciduous—but has successfully adapted to parkland and urban areas, frequently roosting in buildings. Leisler's noctule is rare across most of its range, with one notable exception: Ireland, where it is much more common and represents the island's largest and third most abundant bat species. Ireland is considered the species' global stronghold.

Behaviour & Diet

Leisler's noctule emerges soon after sunset to hunt flying insects, particularly moths and beetles. It flies in a characteristically straight and fast manner with shallow dives, often at treetop level. The species is especially active around dusk and dawn and will travel up to 10 km while foraging. Interestingly, it sometimes feeds around streetlights, taking advantage of the insects attracted to artificial light sources. Breeding typically occurs in small colonies of around 20 to 50 individuals, though Irish colonies can be significantly larger, with some numbering as many as 1,000 bats. Females usually give birth to one or two young, with twins being more common in the eastern parts of its range.

Best Time & Places to See It

Ireland is your best destination for reliably encountering Leisler's noctule, where it is far more common than elsewhere in its range. The bat is most active around dusk and dawn, so plan your wildlife watching during these twilight hours. Look for it emerging from hollow trees or buildings where colonies roost. Observing the species around streetlights in woodland areas or parkland may also prove rewarding, as it actively hunts insects attracted to artificial light.

Photography Tips

Photographing Leisler's noctule presents the typical challenges of bat photography: rapid flight and low-light conditions. Focus on dusk and dawn when light levels are slightly better and the bat is most active. Fast shutter speeds are essential to freeze the swift, straight flight pattern. If the bat feeds around streetlights, position yourself nearby with high ISO settings and a fast lens. The distinctive hairy undersides of the arms and the mushroom-shaped tragus are useful field marks worth capturing if possible, though the bat's speed will demand patience and multiple shooting attempts.