British Bats
Bat Conservation
Introduction
Bats are the most endangered group of mammals in Britain. Their numbers have steadily declined throughout Britain in the past 100 years. The most significant factor contributing to this decline has been the loss of suitable habitat, and the destruction of existing roosts. The lifestyle that bats possess makes them particularly vulnerable to change. The collecting together of large numbers of individuals in one location, as happens at the roosts, means that many bats can be affected at once if these places are damaged or disturbed. Roosts tend to be the focal point for bats which range over a large local area, so if only one roost is lost bats may become extinct over a relatively large local area.
Whereas loss of roosts can cause a sudden large decline in bat numbers, the effect of habitat change is more gradual and subtler, but is equally devastating. Bats like to hunt along hedgerows, woodland edges, and woodland clearings and over ponds. These habitats have declined in number and quality in recent decades due to changes in agriculture. Agriculture is now much more intensive, and there is no space left for 'scrub' areas, and old techniques such as hedge laying have been replaced by machinery. The result is that habitats have changed. These, and other factors will be discussed in this chapter, as well as ways in which you can help bats.
Bats reliance on man
Bats have a complex relationship with man. Although rarely seen many species of bat are dependent to a lesser or greater extent on man. They rely on us to provide them with suitable habitats in which to forage, and safe places in which to roost. Any changes in how we manage our landscape, or even build our houses can therefore have an unintentional effect on the bats that live around us.
A good example of this is the reliance on man seen by the Daubenton's bat. This species feeds over ponds and lakes.. How we care for and maintain stretches of open water will have an effect on Daubenton's numbers. If we fill in lakes and ponds, less habitat for this species will be available, if we create more water then habitat for Daubenton's Bats will be created. Strangely enough, polluting water courses can help Daubenton's bats, as eutrophication, the enrichment of the water caused by too many nutrients running into the water from agriculture, help provide the food which the insects the Daubenton's bat feeds on needs.
Man often has a beneficial effect on bats. The homes we build, along with other built structures such as bridges, tunnels, mines, and farm buildings have all provided alternative roosts for a variety of bat species. These artificial roosts have undoubtedly s natural roosts, which are often in short supply, and have allowed species to supplemented new areas, or occur at higher densities, than would occur naturally. Some species such as the Lesser Horseshoe Bat, would originally only hibernate in caves, but have been able to adapt to use human structures instead.
We have altered our natural environment considerably, ten thousand years ago, much of Britain was forested, most of which was felled to make way for agricultural land. This has not necessary been bad for all species, some animal species that prefer more open habitats have benefited. A good example of this is the Greater Mouse Eared Bat. Originally this species was probably found only in the south of Europe, and at the edges of the great forests. Man opened up the forests, creating a patchwork of woodland, fields and hedgerows, providing ideal habitat for the Mouse eared bat to expand into. The Greater Mouse Eared Bat is now found over much of central Europe. However, other purely woodland dwelling species such as the Bechstein's Bat probably suffered, as the habitat they preferred was lost.
Why Bat Populations Have Declined
Changes in Farming
Farming has changed substantially in the past 60 years. Farming is a business like any other industry and farmers have had to modernize and change their practices to cope in the modern world. Unfortunately many of these changes have been to the detriment of wildlife. Subsidies encourage farmers to be much more intensive. This has meant that scrub areas have been cultivated and valuable areas for wildlife lost. Mechanization has meant that larger fields are easier and more economical to manage, and so hedgerows that provide ideal bat hunting grounds have been lost to enable fields to become bigger. Ponds have been lost because they are no longer needed for providing drinking water for livestock. Farming in the modern era is now much more specialized, with mixed farms being relatively uncommon, and the mosaic of habitats that they produced disappearing. All this has resulted in farms that are much more uniform and a lot less varied.
These changes have not killed bats directly, but the use of pesticides and insecticides has. From the 1940s many new chemical compounds were developed to use on crops to kill pests and weeds. Many of these chemicals were poisonous to wildlife. DDT being amongst the most famous of them. These did not kill bats immediately, but instead built up slowly in their bodies when they ate contaminated insects. The DDT would be deposited in their fatty tissues over time. During the winter hibernation as the fat was broken down to keep the bat alive, the DDT was then released, eventually giving the bat a lethal dose. Another problem caused by insecticides is that they kill many of the insects that the bats rely on for food, thus by using insecticides the food supply of bats is reduced. Since the 1970s the problems wit inorganic pesticides has gained much attention and they have been gradually banned. Despite the banning of most of the very dangerous chemicals, less deadly pesticides and insecticides are still widely used.
Changes around our homes
Unfortunately bats are being made increasingly unwelcome in and around our homes, mostly unintentionally rather deliberately. For a variety of reasons our homes are being put into a better state of repair. This could be because we are wealthier, the rise in interest in DIE programs, or because longer lasting building products and fixtures such as PVC doors and windows are now common. Many loose tiles or gaps between eaves, which offer chances for bats to roost, are being sealed up or blocked. PVC window frames and facias are more durable than the old wooden ones, which used to provide plentiful opportunities for bats to gain entry. Another problem are converted buildings. Abandoned buildings such as derelict outbuildings and barns are now much less common that they used to be. Many are being converted into housing, while others are being demolished. These buildings used to provide ideal roosting areas for bats but are now disappearing.
Another problem associated with the increased interest in keeping our homes in good repair is that now many people use wood preservatives in their lofts and attics. Many of these people unwittingly use preservatives that are toxic to bats, and so end up killing bats that they did not even know were present. Lastly there are a small number of people who either do not like bats, either because they believe they carry disease, or because they believe they will cause damage to their property. Many people are unfortunately intolerant of wild animals, and believe they belong 'outside'. Often these people are misinformed or ignorant about bats, and will often change their position if they are educated about bats and the time is spent in educating them about why bats need these areas in which to roost. However, these are the type of people who will kill bats or try to prevent them access to their homes, even though this is now illegal.
Changes in Forestry
Although many bats use the opportunities offered by man, and will happily inhabitant human dwellings, most bats still hunt in woodland areas, and some such as the Bechstein's Bat are still predominately woodland living. Woodland remains an important habitat for bats, and the way it is managed will have important effects on the bats that live there. Only a few thousand years ago Britain was for the most part completely forested. This provided ample roosting sites for bats. As the forests were unmanaged, dead and decaying trees were left to rot in situ, providing excellent accommodation for woodland roosting bats. However, since this time, substantial area of forest have been cleared, mostly to provide agricultural and pasture land, and also for timber. This has led to Britain becoming one of the least forested countries in Europe. Although these changes helped some species by creating habitats they preferred such as open meadows or woodland edges, many of the purely woodland living species of bat suffered.
Woods have also become increasingly managed. Forests were heavily managed to try to provide steady supplies of timber, and also to fit in with Victorian ideals of order. Dead trees were removed, thus depriving bats of valuable roosting places. Trees began to be planted in uniform stands, all of the same age, because this eased management, but which also provided much less varied habitats for wildlife. Clearings and breaks in the tree canopy were discouraged, thus reducing the amount and number of valuable 'woodland edges' many species of bat use for hunting. It is only in recent years that forestry management has become much more sympathetic to the needs of wildlife. Now it is common for dead trees to be left standing, and gaps and rides are now often artificially created in order to provide the varied habitats that many species of animals, not only bats require. Altogether woodlands are now much more naturally managed. Despite this Britain still has a low amount of woodland, but many local authorities and conservation organizations are now working to increase the amount of forested land.
To read about a bat conservation project that I took part in in Berlin please click here.