Brandt's / Whiskered

 Differences lie in the shape of the inner lobe of the ear (the tragus), penis and features of the teeth (the shape of the 3rd upper pre-molar). Brandt's has a large cusp at the base on the inside of this tooth. The cusp is bigger than the tiny tooth next to it. Whiskered bats have a small cusp  or no cusp.

In the paper "Identification of Whiskered and Brandt's bats" by Lene Berge from the 'Bat Ecology and Bioacoustics Laboratory', University of Bristol (presented at the National Bat Conference, University of Reading, September 2006) pdf 15Kb, Lene Berge says:

"I suggest that the best way of distinguishing between the two species is by using a
combination of upper jaw dentition, penis shape, tragus shape, thumb claw length and lower
jaw dentition. Identification should then be based upon how many features correspond with
each species. However, until a feature with no overlap between species has been detected or
identification can be verified using molecular methods, all identification of whiskered and
Brandt’s bats should be regarded with some caution. On the other hand, it is still important to
keep in mind that the five features mentioned above, used in combination, did classify 100%
of the bats correctly and that each of these features when used separately could classify over
80% of the bats to the correct species".

Whiskered and Brandt's bats were only separated as distinct species in 1970. Thus much of the information previously applied to Whiskered bats might relate to either species and the difficulties in telling them apart, even in the hand, makes the identification of differences in their behaviour and ecology also difficult.

Whiskered and Brandt's bats are found throughout England and Wales and Whiskered to southern Scotland. It is possible that Brandt's is actually more common and widespread than Whiskered in parts of Great Britain. Whiskered is also found throughout Ireland.

Both are found through most of Europe, occurring as far north as Scandinavia but absent from the south and west of the Iberian peninsula. DNA work in Germany has shown that there is a second, as yet unnamed, species of Whiskered bat there.

 Whiskered and Brandt's bats are vulnerable to the effects of modern agricultural practices and decline of woodland, which result in the loss of suitable feeding habitats and hollow trees for roosting. They are susceptible to pesticides, especially those used as remedial timber treatment chemicals. Disturbance and vandalism of their hibernating sites, caves and tunnels, is an additional threat.

flight & ultrasound

Both species emerge within half an hour of sunset and probably remain active throughout the night. Whiskered bats have a fast and fluttering flight, to a height of 20m, generally level with occasional stoops. They glide briefly, especially when feeding in the canopy. They frequently fly along a regular path over or alongside a hedgerow or woodland edge. Brandt's bats have a rapid and skilful flight, flying at a medium height and more often within woodland. Prey is occasionally picked off foliage.

Whiskered/Brandt's bats have an echolocation range of 35 - 80 kHz with a peak intensity at 60 kHz. Their calls are quieter than Daubenton's bat. On a heterodyne bat detector a regular series of clicks throughout the frequency range can be heard but the sound can sometimes be distorted when the bats are turning. May easily be overlooked as a Pipistrelle except for the higher frequency of peak intensity.

  Brandt's call on a Heterodyne bat detector.

  Whiskered call on a Heterodyne bat detector.

  Whiskered call on a Time Expansion bat detector.

breeding

Mating usually takes place in autumn but has been observed in all winter months. Adult females segregate from males in the summer to form maternity colonies. Summer roosts are occupied from April/May until July/August, sometimes until October with occasional winter records.

Females give birth to their single young in June or early July. The baby is fed solely on its mother's milk. By 3 weeks it is able to fly and by 6 weeks can forage for itself. Some females reach sexual maturity at 3 months (in their first autumn) but the majority do not mate until their second autumn.

summer roosts

Both species are regularly found in buildings, though colonies are more commonly found in the north and west. They are found in all types of houses including some modern ones but particularly in older buildings with stone walls and slate roofs.

Both species are mainly crevice dwellers. Roosts can be under hanging tiles, above soffits, in cavity walls, above roof under-boarding or along the tunnel under ridge tiles. They can also sometimes roost in exposed positions in the roof space under the ridge beams.

Droppings frequently accumulate in the roof below the ridge and especially below the favoured roost sites but not particularly at gable ends or on chimneys. Colonies of Whiskered and Brandt's bats may use separate parts of the same roof as Whiskered, Pipistrelles or Long-eared bats.

winter roosts

Brandt's bats are regularly found hibernating in caves and tunnels, but almost always in small numbers with only a few sites recording more than 20 individuals. Thus, in Britain, they seem to have a limited reliance on underground sites and the hibernation sites for most of the population remain unknown. Some of the regular sites in south-east England are barely underground; such as the exposed relict entrances to disused lime kilns.

Within cave sites, Whiskered bats are usually found in cold areas close to the entrance, but occasionally roost in the warmer interior. They may choose more humid situations than Brandt's bats. Whiskered bats more often hang exposed, whereas Brandt's bats often lodge in tight crevices and can be found among clusters of other species. Males may stay in the hibernation sites until well into May.

Description
Head and Body Length	35 - 50 mm
Forearm Length	30 - 39 mm
Wingspan	200 - 250 mm
Weight	5 - 9g
Colour	Fur dark grey or brown, golden tips on back, greyish underneath. Face and ears dark brown or black Brandt's bat's face and base of ears often pinkish.
Life Cycle
Mating Period	Autumn and winter.
Maternity Colonies	Established late spring. Young: 1 born end of June to early July, weaned at 6 weeks.
Colony Size	30 - 200
Longevity	Up to 20 years (Brandt's) and 20 years (Whiskered).
UK Status	Vulnerable.
Habitat and Food
Summer Roosts	Mainly buildings, trees.
Winter Roosts	Sometimes caves and tunnels.
Feeding Habitat	Wooded country, often near water.
Food	Moths, other small insects and spiders.

further reading

"Echolocation signals reflect niche differentiation in five sympatric congeneric bat species" (2004) (pdf 264Kb).

"Flight and echolocation behaviour of whiskered bats commuting along a hedgerow: range-dependent sonar signal design, Doppler tolerance and evidence for 'acoustic focussing' " (2006) details