Bat box
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A bat box is an artificially created roost for bats , in which the nocturnal animals stay and sleep during the day , in which they give birth and raise their young, or in which they mate or hibernate . The design and location of the box differs significantly depending on which bat species and what use the box is intended for.
history
Unlike nest boxes for the songbirds popular with the population, which have been known for a long time, bat boxes did not spread until the second half and especially towards the end of the 20th century. This is probably due to the fact that bats were viewed with reservations by many people in the past. For a long time, bat protection remained the area of interest of only a few, specialized conservationists, and so bat boxes remained largely unknown to the general public, although the first ideas were developed in the 19th century. Only in the course of the strengthening nature and environmental protection movement were bats recognized by more and more people as a species group worth loving and protecting, and bat boxes were therefore also popular.
From the mid-20th century onwards, the design of bat boxes was influenced by a .:
- Brigitte and Wilhelm “Willi” Issel, researcher couple, zoologists of the working group for bat research in Bavaria
- Bodo Stratmann , teacher and conservationist from Saxony-Anhalt (at the time part of the GDR)
- Alfred Nagel , bat expert at the Zoological Institute of the University of Frankfurt
These pioneers developed a number of construction principles and type designations for boxes that have been tried and tested to this day for self-construction and are also offered ready-made for sale by various commercial manufacturers (Schwegler, Strobel, ...).
Requirements for design and location
Requirements for the target group's habitat
The bat species occurring in Europe are roughly divided into two groups, the "forest" and the "building bats", depending on their summer roost. For both groups, the "living space" has become increasingly scarce due to human behavior in recent times. Man tries to counteract this scarcity with artificially created quarters:
Boxes for forest bats
Forest bats live mainly in the wild outside of human settlements, where they either inhabit abandoned woodpecker holes in living trees or cavities in rotten trees or narrow crevices behind the peeling bark of dead trees. However, due to modern forestry , the stock of old and dead wood in forests has decreased significantly. As a result, on the one hand, there are fewer cavities and crevices in rotten trees and, on the other hand, the food sources of the woodpeckers and thus the number of woodpeckers and the available woodpecker holes are reduced.
Boxes for forest bats either imitate the shape of woodpecker or rotting holes in the wood of trees as a round or deep box or, as a flat box, the narrow gaps behind the protruding bark of a tree (→ for details see below in the construction methods section ) or gaps created by wind breaks or lightning strikes .
Boxes for forest bats are usually attached to trees at a height of at least 3–4 m, and more rarely to free-standing stakes. The height makes it more difficult for predators (especially domestic cats ) to access the box and also makes it easier for bats to approach and take off. For the latter, it is also helpful if the area in front of / below the box is free of branches or other flight obstacles. When choosing a location, it is also important to be close to the bat hunting areas with a rich supply of insects. These are found particularly in near-natural forests and in the vicinity of wetlands.
Boxes for building bats
Building bats (also called house bats ) originally come from nature - like all animals - but as a cultural successor they also inhabit human buildings today, where they find shelter in cracks and crevices in the facade or roof cladding or in the beams of open attics . The construction methods of new buildings that are common today and the increasing energy-efficient renovation of older buildings are aimed at sealing the building envelope as completely as possible against drafts and heat loss. As a result, building bats find fewer and fewer gaps in facades and roofs, and open attics are also becoming increasingly rare.
Boxes for building bats are mostly flat or deep boxes (see below) or large-capacity boxes:
The flat boxes, for crevice-dwelling species, are attached to the outside of the building envelope. To facilitate arrival and departure, the box should be hung as high as possible (at least 4 m) and the space below the box should be free of flight obstacles. Depending on the purpose of the quarter (see below), a warm, sunny to partially shaded location, preferably protected from wind and rain, on the south or east side of the house is suitable.
Large-capacity boxes, for species that live in open attics, are erected or hung on / in high structures (bridges, towers, ...). Here, too, a warm location with the best possible weather protection and as free an approach and departure area as possible is advantageous.
Requirements according to the target group's space requirements
The body size (without wings) of the different bat species in Central Europe varies from thumb (e.g. pipistrelle ) to the size of the palm of the hand (e.g. great noctule ). In addition, the number of animals that live together in a colony in a sleeping group varied greatly from species to species and within a species even after the roost was determined (see below). There are species in which the animals like to hang out individually and other species in which - especially in the nursery (see below) - dozens or even hundreds of animals hang tightly together in close physical contact in clusters. There are types that like to hang in narrow gaps with direct back or stomach contact with the wall, and there are other types that need more space because they like to hang freely.
Due to the wide variation in body / group sizes and space requirements, there is not one size and shape for bat boxes that meets the preferences of all species. With a few constructive tricks (see below) you can expand the range of species a little, but the target group is basically limited.
Requirements after determining the quarter
Different requirements apply to bat boxes depending on the type of roost for which the box is intended:
- Winter quarters
- The roost in which bats hibernate must be quiet, have a high level of humidity and be frost-free, but must also not be too warm to ensure hibernation . These complex requirements are usually only met by natural or artificial cavities under the ground or in thick-walled trees or in massive structures. Only special hibernation boxes with particularly thick walls come into question; “Normal” bat boxes, on the other hand, are hardly suitable and are therefore rarely used for wintering. This enables the control and maintenance (see below) of the boxes in the winter months without disturbing the bats.
- Maternity roost
- For the nursery , in which the female animals give birth and raise their young from late spring to summer, a particularly warm and weather-protected location is important, as the newborns are very sensitive to cold and drafts. Since the females in the nursery usually live in groups of at least 20 or, depending on the species, significantly more animals, the box must be large enough to accommodate a correspondingly large colony.
- Summer quarters
- In the summer roost, the males live in spring when they leave the winter roost, the females and their young when they leave the nursery. The summer quarters are inhabited until autumn; some species seek out special mating roosts before flying to their winter quarters. A partially shaded location (e.g. under a roof overhang) is preferable for the summer roost, as the boxes can heat up so much in the blazing sun of midsummer that this would be disadvantageous for some species.
- Mating roost
- In many bat species, mating takes place from autumn onwards, either in summer or in winter. H. no special boxes are needed as mating roosts. In the case of some species (e.g. great noctule bat ), on the other hand, the males seek out their own mating roosts, to which they lure females ready to mate with scent markings and mating calls. These mating dens are occupied by the males, who are sociable during the rest of the year, and defend them against possible rivals. In principle, a box is suitable as a mating den, as is also used as a summer or nursery roost. Since the mating cave only has to offer space for two specimens - males and females - a correspondingly small box is sufficient; so large-sized species also occupy boxes that are dimensioned for an entire colony of a small species.
Construction methods
When building a bat box, many aspects have to be taken into account with regard to its design, which are derived from the requirements listed above for the intended use in each case. In the literature and on the Internet there are a large number of building instructions for the different types of boxes:
Size and shape
Flat boxes
Flat boxes are designed to meet the needs of crevice bats who prefer close contact with the walls. These can be forest bats as well as building bats; accordingly, these boxes can be hung on trees as well as buildings.
If the interior tapers towards the top, then the box is suitable for species of different sizes. By varying the width, a flat box can also accommodate larger colonies and is therefore also suitable as a nursery room.
The slot-shaped opening is usually directed downwards. This allows feces to fall out, arrival and departure are made easier and the box is less often used by birds.
Deep / round boxes
Round boxes or deep boxes (with a rectangular cross-section) imitate the size and shape of tree or woodpecker holes.
Many round boxes are similar to nesting boxes for cave-breeding birds with the difference that the front wall has an elongated hole or slot in the lower area instead of a round hole in the upper area. In fact, there are models on the market that can be converted into a bird or bat box by replacing the front panel as required.
Some deep boxes are divided into several smaller rooms by the use of partitions. The transition to the large-capacity box (see below) is fluid here.
Large capacity boxes
Large capacity boxes are aimed at large species in which a large number of animals live together in a colony. Often the interior is divided by partitions that the animals can cling to.
The size of such boxes ranges from larger deep boxes (border flowing) to small huts (based on open attics or caves), which are either erected on stilts or attached to high structures such as houses, towers or bridges.
Materials and construction
Natural or near-natural materials such as wood or wood-concrete are particularly suitable as building materials for bat boxes . In the case of wood, it is strongly recommended to use it in its natural state without treatment with wood preservatives , as the animals are very sensitive to even the smallest residues of the chemicals. The shorter lifespan of the untreated wood should be accepted.
It is important that the box is well sealed against drafts and rainwater. Caution is required when processing roofing felt ("tar paper"): It must be ensured that the animals cannot be stuck together by bitumen ("tar") dripping down if the cardboard becomes too hot in the sun and thus soft.
Ideally, bat boxes should be constructed in such a way that the animal's droppings can fall out; this reduces the effort for the annual cleaning and inspection of the box (see below).
The rear wall (as well as any intermediate partitions) of the box should be made of softwood so that the animals can more easily claw them to hang and / or the surface should be roughened (at least rough sawn) or provided with transverse grooves. Similar aids for holding on during landing and for climbing into the box are to be provided below the access opening.
The access opening to the box should be kept as narrow as possible; H. just as big as necessary for the species the box is intended for. Most small and medium-sized bat species can easily get into the box through a gap of 20 to 25 millimeters wide; however, the entrance is too narrow for larger, cave-dwelling animals (e.g. cave-breeding birds), for which the box is not intended. Climbing predators (cats, martens, ...) can also reach the bats less easily through the small opening. The disadvantage to be considered is that if the opening is too small, larger bat species that are actually desired are "locked out" of the box.
colonization
Bat boxes are far less likely to be accepted by bats than bird nesting boxes by birds. Since bats prefer to roost in the vicinity of their roost from the previous year, it can take years before a newly hung box is inhabited by bats for the first time. Some boxes are never settled - without a clear reason for this being clear.
Many species frequently change roosts within their territory; it is not uncommon for a box that is occupied one day to remain empty the next day - or vice versa. Such changes can occur even in the nursery phase; the young animals that are not yet able to fly are carried to their new roost by their mothers.
There is some evidence that putting some bat droppings in front of a newly hung box increases the chances of colonization. This is probably explained by the fact that the bats, as sociable animals , prefer to choose places that are already inhabited by other animals of the same species when they are looking for a new roost, and the animals apparently also identify these places on the basis of the droppings that are below the Entrance and exit can be found. For the same reason, it has a positive effect if you hang several boxes of the same type close together.
Control and maintenance
Some types of wood and wood-concrete are well suited for the needs of bats, but they are not very durable and weather-resistant. The boxes can be damaged by moisture, frost, solar radiation and also by excrement or pests. The boxes should therefore be checked and cleaned regularly, at least once a year, and repaired or even replaced if necessary. The time of year for the work should be chosen so that the bats are not disturbed, i.e. preferably in the winter months between November and February, when the bats are usually in their winter quarters.
Bat boxes are sometimes populated by cave-brooding birds , colonizing hymenoptera (wasps, hornets, bees, ...) or by small mammals ( dormouse , dormouse , squirrels , ...), who build their nests in them. Such nests must be removed during the annual inspection. Here, too, it is important to ensure that the foreign nest is not inhabited, as many of the aforementioned animals are protected as well as bats. With regard to foreign nests, self-cleaning flat boxes should also be checked regularly, at least once a year.
If the bats' droppings cannot fall down, depending on the size of the colony, significant amounts of droppings can accumulate within a few months or weeks. This can attack the material of the box and gradually reduces the interior volume until it is uninhabitable. In particular, boxes that are not self-cleaning must therefore be checked, emptied and cleaned once a year. A dry sweep is usually sufficient for cleaning; chemical cleaning agents should be avoided.
In rare cases, bat boxes are infested with pests / parasites ( bed bugs , etc.) in such large numbers that specific cleaning is necessary. However, insecticides should never be used, as the bats are very sensitive to them. Instead, a weak soapy solution should be used.
literature
- Klaus Richarz, Martin Hormann: Nesting aids for birds and other domestic animals . Aula-Verlag, 2010, ISBN 978-3-89104-734-7 .
- Björn M. Siemers: Bats: The practical book . BLV, 2000, ISBN 3-405-15930-X .
- Jürgen Gebhard: Bats . Springer-Verlag, 2013, ISBN 978-3-0348-5037-7 .
- Christian Dietz, Andreas Kiefer: The bats of Europe: know, determine, protect . Kosmos, 2014, ISBN 978-3-440-14649-1 .
- Birgit Gessner: Fledermaus-Handbuch LBM: Development of methodical standards for recording bats in the context of road projects in Rhineland-Palatinate . Ed .: Landesbetrieb Mobility Rhineland-Palatinate, Section Environment / Land Care. Landesbetrieb Mobility Rhineland-Palatinate, Koblenz 2011 ( hochmoseluebergang.rlp.de [PDF]).
- Gerhard Hübner: Bat boxes as replacement roosts: possibilities and limits . In: Reports of the ANL . tape 26 . Bavarian Academy for Nature Conservation and Landscape Management, 2002, p. 151–161 ( anl.bayern.de [PDF]).
- Sarah Hötzl: Guide to bat roosts on buildings . for the diploma thesis "Bat summer quarters on selected building types". Eberswald University of Applied Sciences, October 1, 2009 ( s30a851c338e41b11.jimcontent.com [PDF]).
Web links
- Attaching bat boxes. with instructions for a bat box. In: Fledermausschutz.de. State Committee for Bat Protection in North Rhine-Westphalia in the German Nature Conservation Union (NABU), accessed on August 5, 2016 .
- Bat box tips. (PDF) In: www.all-about-bats.net. BUND Nature Conservation Center Westlicher Hegau, accessed on September 4, 2015 .
- Leaflet for hanging bat boxes. (PDF) In: www.fledermaus.info. March 6, 2007, accessed September 4, 2015 .
- Practical tips and aids for bats in the house and garden. (PDF) Deutsche Umwelthilfe, accessed on June 16, 2016 .
- Bat box. (PDF) Association for animal and environment Nature conservation in Austria, accessed on June 16, 2016 .
Individual evidence
- ^ Gerhard Föhr: History of bird protection and development of nest boxes. In: nistkastenmuseum.de. Retrieved June 16, 2016 .
- ↑ Hübner: Bat boxes as replacement roosts: Possibilities and limits. 2002
- ↑ bat research. Pension "Zur Fledermaus", accessed on June 16, 2016 .
- ↑ Scientific staff. (No longer available online.) Prof. Dr. Roland Prinzinger, archived from the original on August 14, 2016 ; accessed on June 16, 2016 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Overview of bat boxes. A collection can be found in the Julianenhof International Bat Museum . Information sheet. NABU Regional Association Strausberg-Märkische Schweiz eV ( fledermausmuseum-julianenhof.de [PDF]).
- ↑ Commercial bat roosts. In: www.fledermauskunde.de. H.-J. Martin, accessed June 16, 2016 .
- ↑ Building a bat box. In: www.nabu.de. Naturschutzbund Deutschland eV, accessed on September 4, 2015 .
- ↑ Tips for building bat boxes. (PDF) Berne Information Center for Bat Protection, accessed on June 16, 2016 .
- ↑ Build a bat box yourself. Working group environmental protection Bochum e. V. (AkU) in the Environment Center Bochum, July 23, 2000, accessed on September 4, 2015 .
- ↑ Clean bird nest boxes and bat boxes. (No longer available online.) Lower Nature Conservation and Excavation Authority, Kreisfachberatung Landratsamt Ebersberg, archived from the original on September 16, 2016 ; accessed on June 16, 2016 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
