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Lesser horseshoe bat

The lesser horseshoe bat (Rhinolophus hipposideros) belongs to the family of horseshoe bats (Rhinolophidae). Scientists distinguish only one, sizeable genus (Rhinolophus) within the horseshoe bat family. Currently, the genus consists of 77 species, five of which inhabit Europe. The geographical range of the lesser horseshoe bat covers the area from the Iberian Peninsula in Europe to Kashmir in Asia. The species also inhabits North Africa. It lives in uplands and lower regions of mountain areas. In Europe, the most numerous population of the lesser horseshoe bat lives in the Mediterranean Sea area. The northernmost sites have been reported in Western Ireland. In Poland, the habitat of the lesser horseshoe bat covers the Kraków-Częstochowa Highland, the Polish Carpathian mountains (excluding the Tatras) and the Polish Sudety mountains. Single specimens have been spotted in Podkarpacie and Śląsk Opolski area. The most numerous population inhabits the Beskidy mountains.

The lesser horseshoe bat (average weight: 4-8 grams) is one of the smallest bats living in Poland. Its fur is soft and fluffy, light brown or greyand- brown on the dorsal side; the bat's ventral fur is paler and greyish. Juveniles are coloured darker than adult bats. The lesser horseshoe bat has wide and short wings, which are grey and brown in colour. There is also a larger horseshoe bat (average weight: 19-30 grams) in the Polish fauna. It is much bigger and can be found very rarely.

The lesser horseshoe bat's nose is covered with a fleshy growth; its part, surrounding the bat's nostrils, is called a horseshoe - hence the name of the bats. The lesser horseshoe bats send echolocation signals of a frequency of 108-114 kHz through their nostrils, and the flap of skin around the nose helps intensify and direct the signals. The horseshoe bats are able to move their ears, and ear movements are synchronised with the echolocation signal emission.

The lesser horseshoe bat usually roosts in warm attics, mainly in churches, where it forms small colonies (usually consisting of 10-200 bats) - allowing an ideal nursery roost. In the past, the species roosted also in caves and fortifications. The horseshoe bat winters alone or in colonies, always at a distance from other individuals, wrapping wing membranes around its body. The bat's hibernacula include caves, disused mines, abandoned quarries or fortifications. The lesser horseshoe bat chooses rather warm places (6-9oC), where the relative air humidity is high. It is loyal to its roosts and uses them year after year.

The gestation period of the lesser horseshoe bat lasts approximately 75 days. Delivery of the young usually occurs between mid-June and mid- July. A female gives birth to one offspring which becomes self-sufficient after six to seven weeks. Representatives of the species attain sexual maturity in autumn at the beginning of the second year of their lives. In the natural habitat the lesser horseshoe bat's average life span is four to five years although its maximum life span is 29 years and 5 months.

The lesser horseshoe bat is a sedentary species, and it stays in the same area throughout the year. Its feeding areas include forests, orchards, parklands, tree-covered pastures and stony hillsides, invariably within the range of 2,5 km from its roost. The peak of the lesser horseshoe bat's hunting activity is in the early hours of the night. It shows preference for small insects (taxonomic orders of Diptera, Hymenoptera, Lepidoptera, Neuroptera, Coleoptera). It snatches them in mid-air or collects them from the surface of rocks, walls, leaves and tree trunks. Its flight is agile and resembles that of a butterfly. Young bats learn flying while clinging to their mothers.

On the European Red List, the lesser horseshoe bat has been classified as vulnerable (VU), i.e. considered to be facing a high risk of extinction. According to the Polish Red Data Book of Animals, the species is classified under EN category, i.e. endangered species. A dramatic decline in the population of horseshoe bats in Europe (in Poland, reaching over 90%) took place in 1950s-1980s. This came as a consequence of a widespread use of highly toxic pesticides, both in agriculture and forestry. Currently, the population of the lesser horseshoe bat appears to have reached a stable number, and showing an increase in some locations. Nevertheless, it remains a species highly in danger of extinction. The main threats to the existence of the lesser horseshoe bat are: human disturbance in the bat's hibernacula, decreasing number of nursery roosts (improperly conducted renovation of churches) as well fragmentation and loss of foraging habitats, mostly as a consequence of ill-planned infrastructure development.

Wiesław Bogdanowicz
Museum and the Institute of Zoology
Polish Academy of Sciences