Barbastelle bat

Barbastella barbastellus (Schreber, 1774)
Vespertilionidae

Near Threatened

Other names
CatalanRatpenat de bosc
SpanishMurciélago forestal
EnglishBarbastelle bat
FrenchBarbastelle d'Europe
BasqueBaso-saguzar arrun
GalicianMorcego das fragas

Description

Medium-sized bat, with a body length ranging from 45 to 60 mm, a forearm length between 36 and 43 mm, a wingspan between 255 and 300 mm, a tail length between 36 and 52 mm, ears up to 20 mm, and a weight between 5 and 14 g. It shows slight sexual dimorphism, with males usually being smaller than females. The species is unmistakable due to its short muzzle with nostril fissures reaching the lips, and unique trapezoidal ears that, when joined at the center of the head, point forward. The tragus is long and rounded, narrowing at the tip. The skin is typically dark brown, almost black. The fur is silky and black or dark brown, with yellow or white tips, giving it a fawn-like appearance. In the Canary Islands, females tend to be more brownish, and males are darker, with neither displaying the fawn-like coloration. Juveniles typically have slightly darker coloration than adults. Part of the wings and uropatagium are covered with fur.

Il·lustració de Toni Llobet extreta de l'obra Els ratpenats de Catalunya (BRAU Edicions, 2012).

Fotografies

Fotografies d'Oriol Massana Valeriano i Adrià López-Baucells (www.adriabaucells.com).

Distribution

It is distributed throughout much of central Europe but with many gaps in the Mediterranean area. The northernmost point of its distribution is in Sweden, with a single record in Norway, and to southern England. It is also found in the Balearic Islands, Corsica, Sardinia, Sicily, the Canary Islands, Morocco, Turkey, Anatolia, the Caucasus region, and Iran. In Belgium, the Netherlands, and Norway, the species is likely extinct.


Roosts and phenology

In summer, roosts are typically in forests, behind tree bark, in trunk crevices, and even in flat, narrow bat boxes. Natural roosts are often found in mature forests with an abundance of dead trees and cavities, preferably in oak groves, beech forests, and spruce forests. The roosts are usually located at heights between 8 and 10 meters. Occasionally, they seek refuge in human structures such as old buildings or barns. Roosts for breeding in buildings can house up to 100 females, while those in trees usually have around 10-20 females. Breeding colonies in trees often change roosts frequently. One or two pups are born in mid-June and are weaned by six weeks of age. Females become fertile from the first year, and mating occurs in swarming caves, mainly from late August, although it can extend from September to November, depending on latitude.

This species is not considered migratory. In winter, they also roost under tree bark but more frequently use underground roosts. It is a highly cold-resistant species and typically hibernates at the entrance of these cavities, with temperatures close to freezing. These underground roosts can contain thousands of individuals, with the largest recorded in Slovakia and Poland housing 8,000 bats.


Habitat and diet

The species is considered to be confined to a wide variety of forest environments, although it can also be found in parks and open areas with forest edges. Depending on the latitude, it can be found at different altitudes; in the northern part of its distribution, this species is found in lowlands, while in the south, it occurs in more mountainous areas up to 2,260 meters above sea level. Although it is essentially a forest species, it does not seem to have a preference for a specific type of forest. However, it is generally found in mature forests with a complex forest structure containing trees of different sizes and ages and near bodies of water. Surprisingly, in Cappadocia (Turkey), there is a population that has adapted to steppe habitats. It usually hunts near its roosts, with maximum displacements of about 20 km.
This species primarily feeds on nocturnal lepidopterans (moths) but also consumes dipterans, crane flies, and small midges, as well as occasionally beetles and spiders. The barbastelle specializes in hunting tympanate moths, using its auditory organs, which is why it exhibits it's characteristic echolocation. The barbastelle hunts early in the evening and always hunts near forest vegetation, mainly at edges and clearings, although it also forages within forests. Its flight is agile and fast, capturing its prey in mid-air.


Echolocation

Its echolocation is characterized by alternately combining two types of calls at different frequencies and with distinct structures or shapes. Type 1 has a frequency of maximum energy (FME) around 35 kHz and is a concave call, while type 2 is around 40 kHz and is convex. Type 1 is much more intense than type 2 and is typically the more frequently recorded. Both types of calls are generated in the larynx, but while type 1 is emitted through the mouth, type 2 is emitted through the nostrils. During emergences, it emits only type 2 calls through the nose. The pulse duration ranges between 1 and 5 ms. Only confounded with other species of the genus Barbastella, this species is easily identifiable through its acoustic signature.


Status

According to the IUCN Red List, it is considered Near Threatened, with a negative population trend, and is protected by the Eurobats agreement, the Bern Convention, and the European Union's Habitats and Species Directive. Due to this, various conservation projects have worked towards the protection of this species at the European level. It is a rare species throughout its distribution. Its main threats are related to being a sedentary species, the disappearance of its main habitats (mature forests), the adoption of new forestry practices, the use of insecticides, and disturbances caused by tourism and caving in caves, mines, and other hibernation shelters.