Barbastelle Bat

Taxonomy

The western barbastelle was described as a new species in 1774 by Johann Christian Daniel von Schreber, who placed it in the genus Vespertilio, with a species name of Vespertilio barbastellus. The holotype had been collected in Burgundy, France. In 1836 it was placed in the genus Barbastellus, and the first use of its current name combination of Barbastella barbastellus was in 1897 by Gerrit Smith Miller. The name Barbastella barbastellus might be coming from the Latin barba (beard) and stella (star). Viewed from the side, it seems that the upper lip has a beard, or a moustache.

Two subspecies are recognized by Mammal Species of the World (2005):

• Barbastellus barbastellus barbastellus: distributed from western Europe until the Caucasus, with isolated populations in Morocco
• Barbastellus barbastellus guanchae: only found in the islands of Tenerife and La Gomera, Canary Islands, Spain

In addition to morphological measurement, DNA analysis confirmed the presence of an endemic sub-species in the Canary Islands as well as a relatively homogeneous genetic structure among populations of the Iberian Peninsula and Morocco, and probably, across Europe as far as the Thrace region.

Description

The barbastelle is a medium-sized bat, with a characteristic pug-shaped nose. The ears are broad, joined across its head by skin, and covered in gingery-brown fur on the rear surface. The tragus is triangular – broad at the base but with a nearly parallel tip which starts about halfway along its length. Head and body length is between 40 and 55 mm and wingspan is between 260 and 209 mm. Forearm length is 35 to 45 mm and body mass is 6 to 13 g.

Habitat

Barbastelles roost in splits or behind loose bark of trees all year, generally in mature deciduous forests, as well as rock crevices and within human buildings. In central Italy, tall dead beech in unmanaged woodland were found to be preferred as roost trees. While barbastelles typically remain within a single roosting area, they move between individual roosts with great frequency.

Barbastelles migrate to underground roosting sites over the winter, although they may stay within arboreal roosts in the beginning of the season. Winter roosting sites include natural caves and human structures such as basements, mines and bunkers. Barbastelles are relatively resistant to cold conditions, and are typically found hibernating in cold sites and in exposed positions.

Hunting and feeding

Barbastelles feed chiefly on moths, as well as on flies. Research from Switzerland showed that the biologically most productive parts of the forest are exploited in priority by this species while hunting and that ca. 99% of prey by volume consisted of Lepidoptera. More recent studies confirmed this predominance of Lepidoptera, underlining that medium-sized and larger specimens are targeted in priority by the barbastelles. However, seasonal diet changes were recorded during autumn due to potential interspecific competition (with Plecotus austriacus) and strong decrease of flying larger moths.

The diet of the barbastelles appears to be one of the narrowest among European bats. This specialization in foraging habits probably points to a higher vulnerability of this species to negative changes in the abundance of moth populations. This could explain its current rarity throughout most of its range.

While foraging, barbastelles behave as typical aerial-hawking bat species despite the fact that they hunt exclusively just above the forest canopy. This peculiar foraging technique could be explained by the co-evolution with the defence system of its prey.

Specimens can travel up to 20km per night for foraging purposes and nonreproductive females forage at greater distances than reproductive females

Reproduction

Individuals reach their sexual maturity after one or two years. After total sexual segregation during most of spring and summer, the mating period starts at the end of summer, sometimes during swarming episodes. The mating period is often finishing with the start of the hibernation, but some cases of late mating during winter and early spring have been observed

Around May-June, each pregnant female gives birth to 1 or 2 newborn juveniles which she breastfeeds up to 6 weeks.

Echolocation

The barbastelle has two main call types used for echolocation. The frequency parameters of call type 1 lie between 30–38 kHz, have most energy at 33 kHz and have an average duration of 2.5 ms. The frequency parameters of call type 2 lie between 29–47 kHz, have most energy at 38 kHz and have an average duration of 4.1 ms.

Major prey for the bat order Chiroptera is the moth order Lepidoptera. To minimize the risk of the bats' echolocation, moths (and in rarest examples, butterflies) have evolved to detect the echolocation calls of hunting bats, and use evasive flight manoeuvres, or reply with their own ultrasonic clicks to confuse the bat's echolocation. The Arctiidae subfamily of Noctuid moths uniquely respond to bat echolocation with three prevailing mechanisms: startle, sonar jamming, and acoustic aposematic defence. All these defences depend on specific environmental settings and the type of echolocation call; however, these responses are not mutually exclusive and can be used by the same moth for defence.

In response some bat families are known to use clicks at frequencies above or below moths' hearing ranges. This is known as the allotonic frequency hypothesis. It argues that the auditory systems in moths have driven their bat predators to use higher or lower frequency echolocation to circumvent the moth hearing. Barbastelle bats have evolved to use a quieter mode of echolocation, calling at a reduced volume and further reducing the volume of their clicks as they close in on prey moths. The lower volume of clicks reduces the effective successful hunting range, but results in a significantly higher number of moths caught than other, louder bat species. Moths have further evolved the ability to discriminate between high and low echolocation click rates, which indicates whether the bat has just detected their presence or is actively pursuing them. This allows them to decide whether or not defensive ultrasonic clicks are worth the time and energy expenditure.

Distribution

This species is rare and most of the time decreasing throughout its range. Some historical data from the 19th century refers to the presence of western barbastelles in Senegal. This data is considered as doubtful.

Albania

So far, only four specimens of this species were recorded in Albania. The specimens were caught in 2005 near the Shebenik-Jabllanicë National Park, close to the border with Northern Macedonia. This national park is well known for its beech forest, part of the UNESCO site "Ancient and Primeval Beech Forests of the Carpathians and Other Regions of Europe".

Belgium

Barbastelle bats are known to occur within the Sonian Forest of Belgium.

Ireland

This species was reported in 1997 from the west coast of Ireland, based on echolocation calls. Recent surveys and researches assessed this data and concluded to a mis-identification of the echolocation calls, and the absence of this species from the island of Ireland.

Montenegro

The species is present during summer in both Mediterranean and Alpine biogeographic region of Montenegro, on altitudes as low as 80 m and up to 1.700 m a.s.l.

Netherlands

The barbastelle has been extinct in the Netherlands since 1984.

Norway

It was considered extirpated in Norway, having only been sighted in 1896, 1911, 1913 and 1949. However, it was again found in 2004 and 2008.

United Kingdom

In Britain, only a few breeding roosts are known; Paston Great Barn in Norfolk, parts of Exmoor and the Quantock Hills in Devon and Somerset (see Tarr Steps), Wimpole Wood in Cambridgeshire, the Mottisfont woodland in Hampshire and Ebernoe Common in West Sussex. The UK distribution can be found on the National Biodiversity Network website here.

Conservation

This species is protected in the European Union under the Habitats Directive, meaning that habitats and roosts use by this species may be considered for notification as a Site of Special Scientific Interest. This species is also listed in the Berne Convention and is specifically targeted by the UNEP-EUROBATS convention. Several national legislation are also protecting this species and its habitats in many countries and regions.

In order to highlight the importance of protecting this species at the European scale, this species was selected as bat species of the Year 2020-2021 by the pan-European NGO BatLife Europe.

Status

This species is classified as Near Threatened (NT) in the worldwide IUCN Red List, while it is considered as Vulnerable (VU) at the European and European Union scale and Near Threatened (NT) in the Mediterranean Red List.