bat boxes intro

The steady deforestation of much of Europe this century has led to loss of wildlife. Concerned conservationists became interested in replacing some of the lost natural habitat with artificial habitat through the 19th and 20th centuries. The first design for an artificial roost box for insectivorous bats was published in France in 1918. In central and eastern Europe between the world wars, many boxes were established for birds and also for bats. Much of the motivation was economic, to help control insect pests of tree crops. There was much experimenting with designs

Experiments in Britain started in May 1968 where 26 boxes were positioned in Dorset. Within 5 months, the first bat was found using a box and even earlier, droppings found in boxes showed bats had visited. In the 1980s, a large experiment involving 3000 boxes right across the UK was coordinated by the Institute of Terrestrial Ecology, with the Forestry Commission and the World Wildlife Fund

In 1993, Bat Conservation International developed The Bat Builders' Handbook, describing a variety of box designs that had been tried in the USA

Use of bat boxes in Australia developed out of these projects, with designs that had been published in the UK being circulated in various publications and leaflets in Australia.

One project started at Organ Pipes National Park in Victoria (26 km northwest of Melbourne) in 1992, with 10 boxes. The first sign of use by bats was observed just over 2 years later, and a monitoring and banding project started in November 1994, which is still continuing. More boxes have been positioned on trees in the valley of Jackson's Creek which flows through the park, so now there are 34. Early results were reported in the Victorian Naturalist in 1995 vol 112 (5), and a poster displayed at the ABS conference at Naracoorte in 1996. This brought into contact other people interested in bat roost boxes, conducting projects with results as yet unpublished.

Further papers about the Organ Pipes project presented at the 1998 and 2000 ABS conferences aroused more interest, and a growing correspondence started with people elsewhere in Australia who were already conducting bat box projects or intending to get started and wanting advice.

In 2000 the Field Naturalists Club of Victoria branch in the Latrobe Valley (250 km east of Melbourne) initiated a project to publish a kit of materials to assist anyone interested in starting a bat roost box project. A small team sought help from various people on bat biology, bat species known to live in their area, bat box design and monitoring. A launch of the initial kit produced was held in Morwell National Park in February 2001. The West Gippsland Catchment Management Authority took on responsibility for funding the project, publishing and disseminating the kit, which was eventually ready for release in November 2000. It can be obtained, free of any charge in Australia, via Lorraine Wregg at the WGCMA, and ordered via email at westgippy@wgcma.vic.gov.au

Regrowth forest is becoming increasingly widespread around Australia. Often there are no, or very few, remaining old trees with natural hollows, so if hollow-roosting bats are to have roosting sites, these must be supplied artificially. This practice is likely to increase in future years. Very little is known about the preferences of various hollow-roosting species in terms of box height, entrance slit size, timber thickness, or roost density per hectare. All of this is information which could be obtained from projects monitoring sets of roost boxes

In April 2001 a Bat Roost Box Network was set up, to bring into contact people with an interest in bat roost box projects or in making and selling boxes. To date it has a mailing list of 45, over half in Victoria and most others in the remaining eastern states: 5 in NSW, 4 in QLD, 1 in Tas, with just one in WA. There are sure to be other projects we have not yet heard of, especially in WA

A newsletter is issued irregularly - 15 by mid-2003 - to inform members of what others are doing and to exchange ideas and designs. Most are issued via email, and a few paper copies by post. There is no membership fee at present.

The bat roost box design shown is similar to that used by Robert Bender and Robert Irvine as part of their project in Organ Pipes National Park. It is designed to simulate the roosting habitat of species that roost in tree hollows or behind loose bark. 10 of these roost boxes were installed in 1992, with more added in later years.

Pinus radiata was used in their construction and the expected life of the roost box seems to be less than 10 years. Research in Organ Pipes National Park has shown the width of the entrance slit to be important in the colonisation of roost boxes by microbats, and what species inhabit them (Bender and Irvine, 2001). The most common species found is Gould's Wattled Bat, and this species seems to prefer roost boxes with entrance slits larger than 15mm, although younger bats sometimes use boxes with smaller slits. On a few occasions, White-striped Freetail Bats, (much larger that Gould's) have been found in boxes and these also show a preference for entrances larger than 15mm. The one Mormopterus bat found also occupied a box with entrance slit of 15mm. Forest Bats (Vespadelus species) are most commonly found in boxes with smaller entrance slits, around 12mm. Large and Southern Forest Bats are often found together in these boxes

Bats prefer an entrance at the bottom, hence the alternative design. Roughen all internal surfaces with shallow horizontal saw cuts. Use 25mm rough-sawn timber. You could experiment with hanging some hessian from the inside roof or reduce the cavity. Shape and size of your bat home is not critical, but front and back depth should not exceed 100mm because bats like narrow spaces.
Install on a tree clear of branches, or on a wall of the house under the eave. Internal dividers and greater dimensions will potentially house a larger colony. Bats prefer tight surrounds. Don't open the box when it is occupied by bats. Watch at dusk for exit of bats. Spraying the box with guano (bat droppings) and water may help to attract bats. There must be a tight seal at all joints to avoid draughts.
Reproduced with permission. These designs are part of the Bat Roost Box Kit, 2nd edition 2003 and published by the West Gippsland Catchment Management Authority. The Kit is available free of charge by contacting the Authority. WGCMA PO Box 1374 TRARALGON VIC 3844 Ph. (from within Australia) 03 5175 7810, email: westgippy@wgcma.vic.gov.au

Stebbings, R. E. & Walsh, S. T. (1991) Bat Boxes: A Guide to the History, Function, Construction and Use in the Conservation of Bats, Bat Conservation Trust, London, 3rd ed.

Tuttle, M. D & Hensley, D. L. (1993) The Bat Builders' Handbook, Bat Conservation International, Texas

Irvine, R. & Bender, R. (1995) Initial Results from Bat Roosting Boxes at Organ Pipes National Park, Victorian Naturalist 112 (5) pp. 212-217

Bender, R & Irvine, R. (2001) Bat boxes at Organ Pipes National Park, Australasian Bat Society Newsletter 16, March

De Souza-Daw, R. (2000) Bat Roost Box Kit, West Gippsland Catchment Management Authority

Rhodes, M. (2001) Roost ecology and conservation of insectivorous bats in suburban Brisbane: An assessment of natural roost habitat of the White-striped Freetail-bat (Tadarida australis), and artificial roost habitats (bat boxes) for insectivorous bats in Brisbane, Australasian Bat Society Newsletter 16, March.