Bat Biology and Species Information

Family, Appearance and Lifestyle     

There are over a thousand species of bat worldwide, of which 16 are known to breed in the UK. Bats are the only mammals that are capable of true flight. They are extremely small animals and a pipistrelle bat will fit inside a matchbox. Their front limbs have become extremely modified and their finger bones, in particular, are very fine and elongated and support a thin skin thus creating wings. Of the British species, two belong to the Rhinolophidae, the horseshoe bats, and the other 14 belong to the Vesper or evening bats. In their roosts horseshoe bats can be distinguished from other species by hanging freely by their feet with their wings wrapped around their bodies, while the other species tend to roost out of sight in crevices.

Range, Habitat, Territory and Home

The places bats use for shelter are known as roosts and these are protected by law (see legislation) whether or not the bats are present. Roosts vary depending on species but can be roof spaces of houses, cracks in the walls of an old barns, disused factory buildings or tree hollows. They are most often found near feeding areas such as woodlands, hedgerows and water bodies. Bats hibernate in the winter, sometimes in hollow walls or otherwise underground in caves, mines, tunnels and cellars.

Activity (including hibernation) and Social System

As there is little food available for bats in the winter months, these animals hibernate, occasionally rousing on mild nights to feed. They emerge from hibernation in late March or early April and re-gain weight, lost in the winter, before the females collect to breed. Bats generally give birth in June and disperse from their maternity roosts when the young become independent. They mate in the autumn and go back into hibernation during October.

Food

All British bats are nocturnal and feed on insects, including beetles, moths, flies and midges most of which they hunt on the wing, navigating and locating their prey using echolocation, which means that they can forage even in complete darkness. These echolocation calls are species specific and thus can be used for identification. Some bats hang up to deal with large prey such as moths, discarding the scaly wings which have little nutritional benefit.

Breeding – mating, season, numbers

Bats spend most of the year in social colonies. Females form maternity roosts during the summer months, where they give birth and rear their single young. Mating takes place during the autumn and winter but the males’ sperm is not absorbed until the following spring, when bats have emerged from hibernation.

Threats

The greatest threats to bats are as a result of human activities. Bat roosts often occur in buildings and so construction, demolition and restoration works can be particularly harmful. In the past, timber treatments contained chemicals that were harmful and sometimes lethal to bats and, although safer alternatives are now being manufactured, bat populations have been severely affected.

Post-war agricultural intensification increased pesticide use, leading to a fall in the invertebrate fauna, reducing available prey for bats. Hedgerows are important to commuting bats and many were lost during this period, making it more difficult for bats to navigate around the countryside.

Further reading

Dean Waters and Ruth Warren (2003). Bats. The Mammal Society.

Tony Mitchell-Jones (2003). Focus on Bats. English Nature.

Frank Greenway and AM Hutson (1990). A Field Guide to British Bats. Bruce Coleman Books.

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