Details the threats to bats, their need for conservation plus general and species specific guidance on habitat management.
Bats are intriguing animals – the world's only true flying mammals and one of the most diverse mammal groups on Earth – second only to the rodents in number of species, they occur on every continent except Antarctica. There are more native species of bat in the UK – 16 breeding and several vagrant visitors – than any other group of mammals.
Throughout Great Britain and Northern Ireland – as elsewhere in Western Europe – bat populations have declined dramatically in recent years. Conservation of bats is complex and needs to take account of several factors, including the protection of summer roost sites, the protection of winter hibernation sites, and the protection and appropriate management of habitats where bats feed. The bat workers' manual (see page 41) deals with roost site protection.
The aim of this manual is to provide land owners, land managers and their advisors with both general and specific guidance on how to manage areas to benefit foraging bats.
Research is increasing our understanding of bat biology and behaviour. Recently, new information has been uncovered about where bats feed and how to best maintain or enhance their favoured habitats. This book is divided into three main parts after this general introduction: the first (Managing habitats for bats) deals with general habitat management advice to assist foraging bats; the second part (Habitat management for bat species) provides specific habitat management advice for each of the 16 breeding bat species found in the UK. The final section and the annexes provide details of the law protecting bats in the UK, how and where to find more information and some sources of financial assistance for habitat management that can help bats.
Why do bat need our help?
During the 20th century, bat numbers have plummeted in parallel with dramatic changes in the countryside. Several species of bats are now seriously threatened, and in the last decade one species – the greater mouse-eared bat – became extinct as a UK breeding species. Even the more common bats have suffered dramatic declines. Pipistrelle numbers, for example, are estimated to have dropped by about 70% during the 15-year period 1978-1993.
In the UK, bats eat only insects and changes in agricultural practices appear to be an important factor in declining bat numbers. The change from hay making to silage, for instance, has resulted in fewer insects surviving to reach their adult (flying) stage, and hence less food available for foraging bats. Hedgerows and ponds, both widely used by bats, have been lost from the countryside at an alarming rate – even in recent years. For example 23% of hedgerows and 75% of ponds were lost during the period 1984 to 1990. Woodland habitats, including old trees, have declined also. While the overall extent of suitable habitat has been greatly reduced, habitats which remain are becoming more fragmented, and insect availability is falling. Favoured habitats which offer the appropriate conditions where bats can find and hunt their insect prey are essential for maintaining our bat populations. Habitat creation and enhanced habitat management can provide the right conditions to help the recovery of bat populations.
All bats are now protected by law (see Annex I). It is illegal intentionally to kill bats, to disturb them, or to damage their roost sites. Several European wildlife treaties give additional protection to important bat feeding areas. In addition, specific action plans have been prepared for some bats by the UK Biodiversity Group. These 'Species Action Plans' set out how the Government seeks, through partnerships between statutory agencies and voluntary organisations, to reverse the declines and help the recovery of bat populations (see page 41, Biodiversity: The UK steering group report).
Declining numbers is an obvious reason for conserving those bats that remain. But there are other compelling reasons to be concerned about bat conservation. The well being of bat populations mirrors the health of the environment generally. It is our responsibility and in our self-interest to look after the environment now and for future generations, and the conservation of habitats for bats will also benefit a wide spectrum of other wildlife.
Bats are also of direct benefit to land managers. During summer they eat vast numbers of insects each night, many of which are pests that damage growing crops. Pipistrelles for instance, are estimated to each consume up to 3,000 midges or other small flies a night and bats generally feed on the adults of various pest moths including cutworms, chafers, wireworms, and flies such as fever fly and crane fly.
Bats are intelligent, social mammals that can live for up to 30 years. All bats in the UK are relatively small – ranging from our smallest, the pipiestrelle, which weighs around 4-5 g (0.18 oz) and has a wingspan of 20 cm (8 in), to the 40 g (1.4 oz) noctule with a 40 com (16 min) wingspan. Bats sleep in the day and feed during the night, locating their prey by echolocation.
During the summer, bats group together to form colonies in roost sites. In most species, the summer roosts are mainly females gathered into 'maternity colonies' to have their young – bats usually have one young a year. They spend the day in their roosts, which can be found in a variety of buildings, under bridges, in caves or hollow trees, depending on the species (see page 4.1 Bats in houses). Bats are very loyal to particular roost sites and tend to return to the same sites each year. Most summer colonies disperse in September and October, once the young bats are old enough to fly, and many of the bats hibernate at an alternative site from November to April. All bat roosts are protected by law, even when they are unoccupied.
In the UK, bats feed exclusively on insects. Different species have different feeding behaviours. They may catch insects in flight, or pick them off the surface of open water, or from the ground or foliage. In summer, bats emerge from their roosts at dusk to feed. The distances travelled to feeding sites very considerably, both within and between species. While some species feed close to their roost site, like brown long-eared bats, which normally forage within 1 km of their roost, others fly long distances – noctules have been recorded flying more than 26 km to feeding areas. Bats use a number of foraging sites every night, moving between them to locate areas for high insect densities.
Bats frequently return to the same foraging sites on a regular basis, sometimes visiting the same site at the same time each night. However, a large number of feeding areas are needed throughout the year as feeding patterns change in response to insect availability, which, in turn, alters both seasonally and with local weather conditions. Particular foraging sites may be very important to a large number of bats and used by several species at the same time.