Nyctalus leisleri
lesser noctule

Nyctalus leisleri occurs throughout much of Europe and the Middle East. It ranges from the Mediterranean Sea north to Ireland, England, and central Scandinavia and from Portugal east to the Caspian Sea, western Russia and Iran. It is also known in Algeria and Libya in north Africa along the Mediterranean. Throughout its range it is relatively rare except in Ireland, where it is the third most common bat species. (Schober, 1997; Stebbings, 1986; Stebbings, 1988)

Leisler's bats inhabit open deciduous and coniferous forests throughout most of their range. They appear to prefer old growth forest because they requires hollow trees for roosting and hibernation. Parks and estates with ancient trees can provide appropriate habitat. However, Nyctalus leisleri can also be found in agricultural and suburban areas where it utilizes buildings and bat houses as roosting sites. It will forage over many adjacent types of habitat including fields and open water.

This species is migratory and is apparently willing to fly over inhospitable habitat, as evidenced by an individual that was found dead on a glacier at 2600 m. (Schober, 1997; Shiel et al., 1998)

Nyctatus leisleri is a medium to small bat with a wingspan of 260 to 320 mm. Overall length is 83 to 113 mm and weight is between 11 and 20 g. The ears are low and rounded with a mushroom-shaped tragus. This species has somewhat long fur that is dark rufous brown on the back and lighter brown on the ventral side of the body. The dorsal fur is distinctly two-toned, being darker at the base. The face, ears and wing membranes are dark brown to black. The underside of the wing membranes are furred along the body and up along the arms to the fifth finger, hence the older common name 'hairy-armed bat'. The tail membrane extends to the ankles which have well-developed calcars. The tail is short and barely protrudes beyond the membrane. (Schober, 1997; Stebbings, 1986; Stebbings, 1988)

Little is known about the lifespan of Nyctalus leisleri. One individual is known to have lived 9 years in the wild, but other bats in the family Vespertilionidae can live several decades, so this may be a low estimate of the average lifespan. (Schober, 1997)

Nyctalus leisleri has wings that are relatively long and narrow. This morphology is known as high aspect ratio and allows for great speed and endurance but less maneuverability in flight. Endurance is important to N. leisleri since this species is migratory (at least in eastern Europe) and has been known to travel 810 km during a migration. This species hibernates from late September to early April. Nyctalus leisleri is colonial, with as many as 500 individuals sharing a maternity roost, though 20 to 50 individuals is more common. Nyctalus leisleri becomes active early in the evening at or just after sunset. Like other Nyctalus, this species may have two periods of peak activity for a few hours at dusk and at dawn, but is known to forage all night. (Nowak, 1994; Schober, 1997)

Home Range

Nyctalus leisleri may travel up to 10 km from the roost to forage. (Schober, 1997)

Nyctalus leisleri communicates intraspecifically with a number of different vocalizations. Males produce a 'cheeping' call from their mating roosts or in flight to attract females. In maternity colonies, females communicate with each other and their offspring with a variety of squawks, cheeps and trills. In flight Nyctalus leisleri produces complex, songlike calls that may allow bats to identify other individuals and may be used in mate recognition or defense of foraging patches.

While in roosts chemical cues are also important and probably help females identify their offspring. (Pfalzer and Kusch, 2003)

Nyctalus leisleri feeds primarily on small to medium-sized flying insects. It forages at heights up to 150 m, using long-distance echolocation to find prey items. Larger insects are caught individually in flight by aerial hawking. Leisler's bats are adapted for speed, not maneuverability, so they do not glean insects from stationary objects. Nyctalus leisleri is also not thought to be maneuverable enough to capture individual smaller insects. It has instead been observed to fly through swarms of such insects, probably capturing many at one time. (Russ, Briffa, and Montgomery, 2003; Shiel et al., 1998)

The specific diet of this species varies depending on local habitat. In Ireland, where forests are rare, Nyctalus leisleri forages primarily over agricultural areas. As a result, more than 20% of its diet is composed of a single species, the yellow dung-fly (Scathophaga stercoraria), which feeds on the dung of farm animals. Other important foods in pastoral areas include crane flies (Tipulidae), wood gnats (Anisopodidae) and cockchafer beetles (Scarabaeidae). Near water midges (Chironomidae) compose up to 25% of the diet. In wooded areas moths (Lepidoptera), wasps (Ichneumonidae) and lacewings (Chrysopidae and Hemerobiidae) are important prey along with a number of other insects. Non-insect invertebrates such as spiders are also sometimes eaten. (Shiel et al., 1998)

Little information is available on predators of Nyctalus leisleri.

Nyctalus leisleri is rare throughout its range so its role in the ecosystems it inhabits is somewhat limited. Colonies may be locally important predators of flying insects.

In some parts of its range Nyctalus leisleri roosts primarily in buildings because of an absence of suitable hollow trees. This habit may annoy human inhabitats, though the species does not roost in large enough numbers to physically damage the structure.

Nyctalus leisleri feeds on many insects that are considered pests or annoyances to humans.

Nyctalus leisleri is considered rare throughout its range and is protected by local laws throughout Europe. Its preferred forest habitat is patchy throughout its range. Additional lost of forests or the removal of dead trees can only reduce this species' chance of survival. Humans can help provide more habitat for Nyctalus leisleri by installing bat houses or tolerating their presence in buildings.