Deforestation, particularly the loss of old trees, is a problem in many parts of the range and is likely to be causing a population decline. The range is fragmented and the colonies tend to be mainly small. Although there are no precise figures on population decline it seems reasonable to list this species as Near Threatened given what is currently known about the threats, the population numbers and the range. Almost qualifies as VU under criteria A4c.

Nyctalus lasiopterus has a very scattered distribution through central and southern Europe (Iberia to the Balkans, Urals) and north Africa (Morocco (only two records in northwest Morocco), Libya (five records in Cyrenaica), and possibly Algeria (possibly one record in Algeria identified as Nyctalus noctula by Loche 1867, the specimen is lost)). There are an increasing number of records from Turkey (Karatas et al. 2007, Yigit et al. in press). Outside the Mediterranean region the range extends eastwards through Asia Minor to the Caucasus, northern Iran, Kazakhstan and the Urals in Russia. Of the Mediterranean islands, recorded on Sicily. The species is easy to detect with bat detectors, so it is known that the species' distribution in Europe is genuinely extremely patchy. Until 1999, it had been recorded in 120-130 localities in Europe (Benzal 1999). It occurs up to 1,900 m in Switzerland

The patchy distribution and low population density in most of range suggest a relatively small global population. Breeding colonies are typically small (up to 35 females), and few are known. Only two larger-sized (50-100 females) breeding colonies are known in the world. It is rare throughout the range in the Russian Federation (K. Tsytsulina pers. comm.). There is a strong population in northern Hungary. The species is difficult to survey, and difficult to capture with mist nets as it hunts 10-20 m above the ground (K. Tsytsulina in litt. 2005). The population trend is unknown.

It forages over mixed and deciduous forest and wooded river valleys (the latter especially on migration). It is highly dependent on mature forest (the species needs a number of old trees to support a colony, hence any tree removal is a threat). It is largely insectivorous, but is also reported to take small passerines in the southern part of the range during migration. During the bird migration seasons, passerines are likely to form a major part of the diet. Faeces collected during these times are composed 90% of feathers (J. Juste pers. comm. 2007). Tracking the species using radar in Spain it is now known that it flies up to several hundred metres presumably to catch migratory birds.

In summer it roosts in hollow trees, and occasionally in buildings. Rock crevices may also be used as hibernacula in winter. It sometimes roosts with other species such as N. noctula. Nursery colonies are usually relatively small (up to 35 females). Females give birth to a single pup per litter. It is considered to be migratory in the north-east of its range, but there is very little data. Vagrants have been recorded well outside the normal range (Hutterer et al. 2005). Some areas in the western part of the range appear to be occupied exclusively by males, according to capture results. Its foraging range may be greater than 30 km in a single night.

Little is known about potential threats, but loss of mature woodland and loss of or disturbance to roost sites (in old trees and buildings) may have a negative impact on the species. Some individuals were found dead at wind farms in Spain (J.T. Alcalde pers. comm. 2006), and all pups were found dead in 2005 at one of the two known colonies in Spain (located in a city park). The cause of these deaths was not known (J.T. Alcalde pers. comm. 2006). In Spain cutting of old trees which are used as roosts is a threat.

It is protected by national legislation in most range states. There are also international legal obligations for its protection through the Bonn Convention (Eurobats) and Bern Convention, in parts of its range where these apply. It is included in Annex IV of EU Habitats and Species Directive. No specific conservation actions are known. It occurs in a number of national parks and protected areas within its range (K. Tsytsulina pers. comm. 2005). However, in Spain the two known colonies are outside protected areas (J.T. Alcalde pers. comm. 2006). More information is needed on population size and trends, ecology, and potential threats.
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