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Whiskered Bat

The Whiskered Bat is one of the small Myotis species of bats, three of which occur in Britain and two are known in the region. Brandt’s Bat Myotis brandtii is very similar to Whiskered Bat: indeed Brandt’s Bat and Whiskered Bat were only separated in 1970 and so any historical data referring to Whiskered Bats could be either Whiskered Bat or Brandt’s Bat. Whiskered Bats and Brandt’s Bats, while very similar morphologically, have been shown by genetic studies to be more closely related to other Myotis species than to each other (Agirre-Mendi et al, 2004; Niermann et al, 2007). Alcathoe Bat Myotis alcathoe, the third small Myotis bat, was identified in 2001 in Greece and was confirmed as breeding in Britain in 2010. Alcathoe Bat has been recorded in the North York Moors but not yet in the North East. This is a cryptic bat species and with increased survey effort it is possible that it will be found to be present in our region as suitable habitat is likely to be available.

Whiskered Bats are small Myotis bats, distinguished from Daubenton’s Bats Myotis daubentonii and Natterer’s Bats Myotis nattereri by their smaller size, small feet, shaggy dorsal fur and a short calcar which is half the length of the tail membrane. Whiskered Bats have a long pointed tragus with a straight or concave outer margin. The face, ears and membranes of Whiskered Bats are dark brown or black, usually darker then Brandt’s Bat, and the fur is dark or reddish brown, sometimes with golden tips. Differences in the teeth are widely used to separate Whiskered Bat and Brandt’s Bat: in Whiskered Bat the cusp on the interior angle of the fourth premolar is lacking or smaller than the third premolar, whereas in Brandt’s Bat the cusp is obvious and often reaches the same height as the third premolar. This can be seen with the bat in the hand but is hard to determine and dentition can even differ between either side of the bat’s jaw (Harris and Yalden, 2008). Penis shape is also helpful in separating male Whiskered Bats and Brandt’s Bats: Whiskered Bats typically have a thin, straight penis whereas Brandt’s Bats have a club-shaped penis. However this method of identification is uncertain, as a recent study showed that whilst all Whiskered Bats had a thin, straight penis so did 30% of Brandt’s Bats; only 70% had a club-shaped penis (Harris and Yalden, 2008).

Whiskered Bats use buildings for summer roosts, using small crevices such as behind cladding and they are known to hibernate within caves and disused mines. Tree roosts are rarely used. The adult males seem to be solitary and the females form maternity colonies to give birth and to raise their young. Maternity colonies usually comprise 20-60 females, rarely up to several hundred (Dietz et al, 2009). Roost sites can change frequently (every 10-14 days) and in roosts that are occupied for longer there is a high turnover of individuals (Dietz et al, 2009). Whiskered Bats emerge within half an hour of sunset and are known to hunt along regular flight paths when foraging. Whiskered Bats forage in edge or cluttered habitats favouring open areas with patches of woodland or hedges and damp areas; they also use woodland for foraging and will hunt along streams and over water bodies. They have a level flight, often not far above ground level and they are also seen to forage in the tree canopy layer. The echolocation calls of Whiskered Bats and Brandt’s Bats cannot be reliably separated.

The maximum known age for a Whiskered Bat is 23 years (Harris and Yalden, 2008) with an average life span of three and a half to five years (Dietz et al, 2009).

Bolam (1926) notes that the only published record for County Durham for a Whiskered Bat is mentioned by Mennell and Perkins (1864), simply recorded as “Shotley Bridge (?Darlington) W. Backhouse”. Bolam notes that the identification of this specimen was not quite accepted at the time, “a scepticism which subsequent knowledge has proved to be quite unfounded, the Whiskered Bat having now been found to be one of the commonest species in County Durham” Bolam (1926). Bolam found the first specimen of Whiskered Bat for Northumberland lying dead on the grass at Houxty, near Bellingham, on 24 May 1915. He went on to say that this bat was then proven to be numerous in that area as well as Redesmouth, Sidwood, Beaufront and Stocksfield (Bolam, 1926). Current knowledge of Whiskered/Brandt’s Bat suggest that this bat is neither currently widespread or numerous in the region.

As detailed above, Whiskered Bat and Brandt’s Bat are very difficult to separate reliably and the similarities between the two species mean that the existing records need to be treated with care; in the absence of further information the records should all be considered as Whiskered/Brandt’s Bats rather than identified to species level. As a consequence, all specific records referred to in this account are supported by identification criteria.

Whiskered/Brandt’s Bats have a central to western distribution within County Durham and a small number of hibernacula are known to the west of the county. Whiskered/Brandt’s Bats are fairly uncommon in Cleveland with few known roosts and are so far unrecorded in the borough of Hartlepool (Ian Bond pers. comm., 2012). Whiskered/Brandt’s Bats are known from two sites in Middlesbrough.

In Northumberland there are records of Whiskered/Brandt’s Bats spread throughout the county with more records from the southeast section of Northumberland, along the east coast and in the Tyne valley, although it is likely that this reflects survey effort rather than bat distribution. The largest known Whiskered/Brandt’s Bat roost in Northumberland is of 275 bats in Haydon Bridge.

Recent advances in DNA identification techniques have allowed bat droppings to be tested to determine the species of bat present. There have been limited local studies done using this technique, the largest of which was an MSc project undertaken by Helen Jameson in 2010 when droppings were collected from suspected Whiskered/Brandt’s Bat roosts (Jameson, 2010). Bat droppings were collected from 18 sites and 15 samples were DNA tested. Of these, 13 samples produced definitive results: nine samples were Brandt’s Bat, one was Whiskered Bat, one was Natterer’s Bat and two were Daubenton’s Bat. These findings did not reflect the previous understanding of the relative abundance of these small Myotis bats in the survey area. “The most commonly encountered species was M. brandtii which DNA analysis confirmed was present at nine (69%) of the sampled roost sites, despite having only been confirmed previously at three (23%). From DNA analysis alone, M. mystacinus was confirmed as present at only a single site (8%), whereas it had previously been confirmed at seven (54%)” (Jameson, 2010). Selected bat roosts in County Durham that were believed to have been Whiskered Bat roosts were found to have Brandt’s Bat present at the time of this DNA analysis study. This suggests that Brandt’s Bat may be more widespread than previously thought and Whiskered Bat less widespread, although further investigation is required to confirm this. Of the roosts identified in Jameson’s study the Whiskered Bat roost was in Escomb, Durham and five Brandt’s Bat roosts were in Durham and four in Northumberland.

In Northumberland, one site in Hexhamshire is a confirmed Whiskered Bat maternity roost; a female bat which came into captivity was identified by the author on teeth and a DNA test confirmed the species. A single Whiskered Bat, confirmed by DNA, has been found roosting in Cockfield, County Durham.

MARS Whiskered Brandt's bat (2)

Whiskered Bats were caught and tracked as part of a National Trust project at Gibside in 2009-10. The bats were identified in the hand using morphological characteristics. This study confirmed male Whiskered Bats roosting singly or in pairs and also found a maternity roost of around 20 individuals. Five individual Whiskered Bats were radio tracked and a total of eight different Whiskered Bat roosts were found. Of the 70 bats caught during the two year project 16 were identified as Whiskered Bats, suggesting the Derwent Valley holds a good population of these bats. Subsequent catching at this site by the author has confirmed the presence of Brandt’s Bat, based on dentition and a bulbous penis shape.

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Written by Tina Wiffen (last updated Nov 12)