Image: © NBSG Malcolm Fisher
Image: © Bat Conservation Trust Hugh Clark
Image: © NBSG

The Barbastelle Bat Barbastella barbastellus

Barbastelle, Rose Hill Farm, Leavenheath, Essex, April 2012
Image: © Catherine Dew

The Barbastelle is one of 17 species of bats known to breed in the UK.

It is regarded as rare, with the UK population estimated at only 5,000. It is found mainly in southern England, but also in South Wales, not in Scotland or Northern Ireland. Because of its rarity, the Barbastelle is strictly protected, and is also a UK and Norfolk Biodiversity Action Plan Species.

The barbastelle is also considered to be something of a Norfolk speciality - with the population in East Anglia considered to be 'highly significant in context of national distribution'.

The Barbastelle is a medium sized bat weighing 6-13gms with a wingspan of 26-29cms. Its distinctive features are the dark brown/black fur with yellow or cream tips giving it a frosted appearance, and its short, flat face (pug like) with large, almost square ears joined together at forehead.

Barbastelles are woodland specialists. They depend very much on trees in which to roost during the day. Roost sites are usually under flaking bark or in natural cracks and fissures so that dead, dying and damaged trees are very important. The bats can squeeze into very small spaces, only 1-2cms high, where they are safe from predators. After sunset, they emerge from the tree roost to feed, flying through the woodland until dark and then following woodland rides, woodland edges, hedges and watercourses into the wider countryside. Females typically forage up to 7-8kms from their roost, but Barbastelles have been known to forage up to 22kms from the roost.

Like all British bats, Barbastelles feed on flying insects, mainly small moths which they catch in flight. This is known as hawking, whereas some bat species glean insects from foliage at night. They catch their moth prey by echolocation, shouting out high frequency sounds above our audible range, and listening to the echoes bouncing back in their specially adapted ears. This allows them to 'home in' on the moth.

In June, the pregnant female Barbastelles gather together in their maternity roosts in trees, in small groups of 10-20 bats. They usually select a roost which is a suitable temperature to help the developing babies (known as pups); not too cold and not too hot. This is one of the reasons why female barbastelles regularly change roosts, often using several trees in the same area of woodland. The pups are born in late June to early July, usually only one for each mother, (twins are rare), and will quickly learn to grip the nipple under the mother's armpit. They are blind and naked at birth, but the eyes open within the first few days and the fur grows rapidly. The pups stay in the roost while the mothers go out to forage at night, although the mothers may return during the night to feed their young. The pups have to cling tight to the mother if she moves to another roost. The males play no part in raising the young.

The young are fully developed and ready to fly in late July to early August. They will have practiced wing stretching in the roost, but often take some persuading by the mothers to take the first flight.

Autumn is an important time for Barbastelles to feed and put on weight to survive the winter. It is also the mating season, but pregnancy is delayed until the following spring when conditions are favourable and bats can feed again.

Because they are dependent on insects for food, bats hibernate in winter when there are few insects around. They need sufficient body fat to survive the winter period. Barbastelles hibernate in trees, but are sometimes found in barns and underground structures such as ice houses, caves and tunnels. If the weather becomes mild, they may arouse from hibernation and go out to forage and drink. From March, Barbastelles will become more active as temperatures increase and insect prey becomes available. By May, Barbastelles usually forage every night, except when the weather is very wet or cold.

Pregnancy starts in May, and the females will start to seek out the nursery roosts. The males roost singly or in small groups.

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