Brandt’s Bat Myotis brandtii is one of the small Myotis species of bats. They are very similar to Whiskered Bats Myotis mystacinus and this is discussed in detail in the account for Whiskered Bat.
Brandt’s Bats have lighter brown fur than Whiskered Bats and older Brandt’s Bats can have gold tips to their fur. The face, ears and membranes of Brandt’s Bats are brownish and the lower part of the tragus and the ear, including inside the auricle near the base, is paler. Brandt’s Bats have a convex outer edge to their long pointed tragus. The maximum known age for a Brandt’s Bat is 41 years (Harris and Yalden, 2008); this is the oldest recorded age for a bat, discovered from ringing studies in Central Siberia.
Brandt’s Bats roost in trees and buildings but have also been found using bridges and bat boxes; if the roosts are in buildings they are usually close to woodland edges, although two of the three known Brandt’s Bat roosts in the Tees Valley are in suburban houses in Darlington and Guisborough. Like Whiskered Bats, 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 and usually less than 100 animals. Brandt’s Bats hibernate in disused mines and caves and a study has shown that male Brandt’s Bats hibernate for longer than male Whiskered Bats, until May and March respectively (Harris and Yalden, 2008). Brandt’s Bats also choose drier hibernation sites than Whiskered Bats.
Brandt’s Bats tend to have a lower wing loading than Whiskered Bats which may allow them to be more manoeuvrable in flight within a cluttered environment (Harris and Yalden, 2008). Brandt’s Bats are more strongly linked to forests than Whiskered Bats and forage within woodland, on moorland and in damp areas including damp woodland (Dietz et al, 2009).
Whiskered Bat and Brandt’s Bat are very difficult to distinguish reliably and the similarities between the two species mean that the existing records need to be treated with care.
A recent MSc project has suggested Brandt’s Bat to be more widespread in Durham than previously realised (Jameson, 2010). The known Brandt’s Bat roosts have a westerly distribution within the county and the largest count of a known Brandt’s Bat roost was of 300 individuals near Lanchester in 2011.
Durham Bat Group has been monitoring the field centre in Middleton-in-Teesdale in June since 1984 and this site has held varying numbers of Whiskered/Brandt’s Bats. Jameson (2010) confirmed Brandt’s as present by DNA anlaysis of droppings, though an earlier series of DNA samples taken from the Field Centre by Lene Berge had found both Whiskered and Brandt’s to be present (Noel Jackson, pers. comm., 2012). The highest count was 271 bats in 2005 with the lowest counts of 42 in 2009 and 2010.
In Northumberland, four Brandt’s Bat roosts were confirmed by the same MSc project. These roosts are in central and northern Northumberland, with two along the river Wansbeck corridor (Jameson, 2010). In 2011 Brandt’s Bats were caught by the author in Gosforth Park, on the northern outskirts of Newcastle, foraging within woodland but in a suburban setting. These bats were identified by dentition and by penis shape: the male bats caught all had a bulbous penis which currently identifies them as Brandt’s Bats.
Written by Tina Wiffen (last updated Nov 12)