Alcathoe bat

GB: Data deficient

England: Data deficient

Scotland: Data deficient

Wales: Data deficient

Global: Data deficient

Head & body length: 30.8-34.6 mm

Wingspan: around 200-250 mm

Forearm length: 29.7mm – 34.6mm

Weight: 3.5g – 5.5g

Colour: Fur dark grey or brown, reddish hue on the back of mature bats, greyish underneath. Face and base of ears often pinkish.

Alcathoe bat looks so like others in the Myotis group, especially Brandt’s bat and whiskered bat, that it was only first recognised in 2001 as a separate species by bat scientists in Greece and Hungary, followed by reports of it being found across Europe.

Then by using genetic analysis a number were identified in the UK, both in Yorkshire in the North York Moors National Park, and also on the South Downs in Sussex. As these sites are 350km apart, the researchers believed the bat to be resident in the UK but had not been spotted before because it looks so similar to other bat species. Since then, Alcathoe bats have been discovered in a number of other sites in the UK; we even know they can be more common than the other small Myotis species in some places.

Covid restrictions stopped studies for two years, but plans are being made for national small Myotis surveys to start again. They will be looking for the location of colonies and presence of all three small Myotis species, Alcathoe, Brandt’s and whiskered, and hoping to learn more about them.

Although all three are woodland bats, we have to understand their different needs in order to plan for their conservation.

This species forages in densely deciduous woodland areas. They have been found roosting in trees in summer, not far from water; in the autumn they have been seen swarming outside caves.

Alcathoe bats love moths, mosquitoes, other small insects and spiders.

Mating usually takes place in autumn, but Alcathoe bats have been observed to mate in all winter months. Adult females form maternity colonies in the summer, giving birth to their single young in June or early July. The baby is fed solely on its mother’s milk: by three weeks it can fly and by six weeks it can forage for itself.

Some females reach sexual maturity at three months (in their first autumn) but the majority do not mate until their second autumn.

Alcathoe bats echolocate between 120kHz and 43kHz, sounding loudest at 45kHz. Their calls sound like dry clicks (similar to Daubenton’s but not as regular and often slower); they are sometimes mistaken for pipistrelles but their frequency range is much wider.

Alcathoe bats are vulnerable to the effects of modern agricultural practices and decline of old forests, in particular natural riparian hardwood forests and mountain forests. Resulting in loss of suitable feeding habitats and usually oak trees for roosting.

They are susceptible to pesticides, especially those used as remedial timber treatment chemicals. Disturbance and vandalism of their hibernation sites (caves and tunnels) is an additional threat.