Bat boxes: a review of their use and application, past, present and future

Loss of tree cavities presents a threat to tree roosting echolocating bat populations. Bat boxes have been used for over a century to provide artificial cavities. The aims of this review were to provide a synthesis of bat box use in temperate parts of the world, to discuss the applications and effectiveness of bat boxes, to provide box deployment recommendations and to identify areas requiring further research. The 109 publications reviewed originated from four regions. The majority were from Europe (70%) followed by North America (16%), Australia (12%) and Asia (3%). Publications reported box use for research (n = 67), conservation management (n = 42) and public bat awareness (n = 1). The most commonly used bat box designs could be divided into five basic types, four originating from Europe and one from North America. Woodcement as a box material was frequently used in Europe and was practically absent elsewhere with timber boxes most commonly used overall. Seventy-one species of bats have been recorded using boxes, although only 18 were identified as using boxes commonly and 31 species were reported to have formed maternity roosts. The lack of maternity and overwintering roost records in boxes is a concern. There is a need to test current box types across geographical regions and to develop designs further. Where boxes are used as a conservation tool, consideration should be given to the long-term maintenance costs of a box program. Unless known to be unsuitable to target species, boxes should be made from durable materials, be unattractive to non-target species and be ‘self-cleaning’. Deploying a variety of box designs in clusters, time since box installation, non-target species box competition and target species-specific box design elements are likely influencing box uptake. The provision of boxes that comprise different microclimates and box aspects are likely best suited to meet the varying needs of a given tree roosting echolocating bat community. No conclusive evidence was found that box installation height is important for box uptake. There is concern that boxes may provide a competitive advantage for bat species commonly using boxes. Bat boxes should not be used as a justification for the removal of trees that comprise potential roost cavities.