Roads can disrupt the population processes of vertebrate wildlife species through habitat fragmentation and vehicle collision. The aims of this review were to synthesise the recent literature on road impacts on wildlife, to identify gaps in our understanding of this topic and to guide future research and management in Australia. We reviewed 244 published studies from the last decade on road and vehicle impacts on wildlife conducted worldwide. A geographic bias was evident among the studies, with 51% conducted in North America, 25% in Europe, 17% in Australia and 7% across several other countries. A taxonomic bias was evident towards mammals (53%), with far fewer studies on birds (10%), amphibians (9%) and reptiles (8%), and some (20%) included multiple taxonomic groups. Although this bias is partly explained by large insurance and medical costs associated with collisions involving large mammals, it is also evident in Australia and signals that large components of biodiversity are being neglected. Despite a prevalence of studies on wildlife road mortality (34%), population impacts are poorly described, although negative impacts are implicated for many species. Barrier effects of roads were examined in 44 studies, with behavioural aversion leading to adverse genetic consequences identified for some species. The installation of road-crossing structures for wildlife has become commonplace worldwide, but has largely outpaced an understanding of any population benefits. Road underpasses appear to be an important generic mitigation tool because a wide range of taxa use them. This knowledge can guide management until further information becomes available. Global concern about the decline of amphibians should lead to a greater focus on road impacts on this group. Priorities for research in Australia include (1) genetic studies on a range of taxa to provide an understanding of life-history traits that predispose species to barrier effects from roads, (2) studies that examine whether crossing structures alleviate population impacts from roads and (3) studies that describe the behavioural response of frogs to crossing structures and that identify factors that may promote the use of suitable structures. A national strategy to mitigate the impacts of roads on wildlife populations is long overdue and must ensure that research on this topic is adequately funded.
Artificial tree hollows (nest or roost boxes) may be of considerable importance to the conservation and management of Australian hollow-using birds and microbats. This is suggested by recognition that the rate of collapse of hollow-bearing trees may exceed replacement in some landscapes. We review the published literature to synthesise current information on the use of artificial hollows by Australian birds and bats, and to provide guidance to future research and management. The use of artificial hollows has been documented in some detail for 15 native bird and eight microbat species. A range of hollow designs has been employed but there is a limited understanding of favoured designs. General designs (e.g. front-entry plywood boxes) have been used extensively by some species and should continue to be used until more effective designs are identified. Species tend to use artificial hollows that have entrance sizes just sufficient for their body size, and this should guide hollow design. Competitive interactions with a range of non-target species (native and non-native) may have a pronounced influence on artificial hollow use and must be considered in any management program involving artificial hollows. We highlight some design elements that may reduce interference by non-target species. Temperature inside artificial hollows may have a particular influence on their use by bats due to the role of microclimate in bat thermoregulation. Trials are needed to investigate this factor and to inform general approaches to positioning of artificial hollows. Several distinct management uses exist for artificial hollows, including assisting threatened species recovery, e.g. Kangaroo Island glossy black-cockatoo (Calyptorhynchus lathami halmaturinus) and orange-bellied parrot (Neophema chrysogaster). Artificial hollows offer an interim solution to hollow shortage but their full potential will only be realised when preferences for different designs are better understood. This will require a commitment to monitoring and should be conducted in an adaptive management context. Increased knowledge of the use of artificial hollows by Australian birds and bats should be of global relevance to the management of hollow-using species because it provides an independent test of ideas and strengthens any generalisations.
Nest boxes have been recognised as research and management tools for arboreal marsupials in Australia for over 20 years. We review the published literature with the aim of describing the scope of studies conducted in Australia thus far and providing guidance to future research. We recognise three types of application in research: (1) detection of species, (2) study of a species’ ecology, and (3) investigation of box designs preferred by different species. Several species of arboreal marsupial may be detected more readily in nest boxes than by conventional survey techniques, allowing description of key aspects of their ecology; e.g. feathertail glider (Acrobates pygmaeus), eastern pygmy possum (Cercartetus nanus) and brush-tailed phascogale (Phascogale tapoatafa). Identifying the most favoured nest-box design for any species has implications for detection and management uses of nest boxes. More research is needed but preliminary findings suggest that species prefer narrow entrance holes, while height of the nest box above 3 m may be inconsequential. We recognise three types of management application: (1) species introduction, (2) support of populations of endangered species, and (3) strategic placement such as to enhance habitat connectivity. Currently there have been few attempts to use nest boxes to manage arboreal marsupials but further research is needed to realise their potential as a management tool.
Although vehicle-induced mortality of wildlife is well known on roads throughout Australia, few empirical studies describe the extent of this mortality or assess the potential effects on wildlife populations. We recorded 529 roadkills of 53 vertebrate species along a 100-km circuit of three major roads during 20 weekly surveys across winter, spring and summer. This equates to 0.3 road-kills km–1 week–1 or one road-kill every 3.8 km week–1. The most frequently killed native species were the northern brown bandicoot (4 per week), the mountain brushtail possum (2 per week) and the Australian magpie (2 per week). These values are underestimates because our survey technique could not detect all road-kills and ~40% of those left on the roadside disappeared within 7�days. Detailed study of the local population of the brown bandicoot is needed to determine whether such a level of road mortality is sustainable.A logistic regression analysis was used to determine whether any of 10 road and landscape attributes were closely associated with the presence of specific groups of road-kills. Bandicoots were not associated with any measured attributes. Possums were more likely to occur along roads on mid-slopes and ridge-tops. Magpies were associated with roads on ridge-tops. Canopy-dwelling birds were more likely to be killed on 3-lane roads surrounded by dense vegetation.Road-kill surveys such as this are needed to identify species for which road mortality is unsustainable, to determine the influence on threatened species, and to identify important crossing points where road-kills are high. The frequency of road-kill of many ground-dwelling or arboreal mammal species in this study highlights the importance of impact mitigation by road authorities.
Tree‐cavity‐dependent wildlife faces future shortages of cavities due to a decline in the abundance of large, old trees in many parts of the world. Nest boxes are proposed as a tool to restore habitat value but evidence of their effectiveness for arboreal mammals remains equivocal. This may arise from a poor understanding of design preferences. We conducted investigations in two landscapes in eastern Australia to determine whether species show a preference for specific designs. We observed a preference by some mammal species for particular designs (33–78% occupied/used), suggesting that design refinement can improve the frequency with which nest boxes are used. Although feral species may out‐compete target species for nest boxes, we did not observe this. We recorded feral honeybees (Apis mellifera) in 6–9% of nest boxes but they did not remain, and many occupied boxes were later used by mammals. The introduced common myna bird (Acridotheres tristis) was prevalent in one landscape, but competition for nest boxes was localized. For nest boxes to be an effective habitat restoration tool, they must be able to be occupied over long periods of time. We investigated this for the squirrel glider (Petaurus norfolcensis), an arboreal marsupial threatened through part of its geographic range. Squirrel gliders occupied and bred within nest boxes (100% used) at two locations continuously over a 10‐year period with minimal nest box maintenance. Individuals occupied boxes for up to 7 years. This confirms that targeted nest box programs can be an effective restoration tool for cavity‐dependent arboreal mammals.
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