Kylie Soanes

Evidence that a Highway Reduces Apparent Survival Rates of Squirrel Gliders

ABSTRACT. Roads and traffic are prominent components of most landscapes throughout the world, andtheir negative effects on the natural environment can extend for hundreds or thousands of meters beyondthe road. These effects include mortality of wildlife due to collisions with vehicles, pollution of soil andair, modification of wildlife behavior in response to noise, creation of barriers to wildlife movement, andestablishment of dispersal conduits for some plant and animal species. In southeast Australia, much of theremaining habitat for the squirrel glider, Petaurus norfolcensis , is located in narrow strips of Eucalyptus woodland that is adjacent to roads and streams, as well as in small patches of woodland vegetation that isfarther from roads. We evaluated the effect of traffic volume on squirrel gliders by estimating apparentannual survival rates of adults along the Hume Freeway and nearby low-traffic-volume roads. We surveyedpopulations of squirrel gliders by trapping them over 2.5 years, and combined these data with priorinformation on apparent survival rates in populations located away from freeways to model the ratio ofapparent annual survival rates in both site types. The apparent annual survival rate of adult squirrel glidersliving along the Hume Freeway was estimated to be approximately 60% lower than for squirrel glidersliving near local roads. The cause of the reduced apparent survival rate may be due to higher rates ofmortality and/or higher emigration rates adjacent to the Hume Freeway compared with populations nearsmaller country roads. Management options for population persistence will be influenced by which of thesefactors is the primary cause of a reduced apparent survival rate.Key Words: Australia; emigration; mortality; population persistence; road ecology; squirrel glider;survivalINTRODUCTIONThe global decline in biodiversity is directly linkedto anthropogenic activities such as the modificationof landscapes and environmental systems (Kerr andCurrie 1995, Lande 1998). Increasing humanpopulation size and technological advancementfuels the development of agriculture, housing,industries, forestry, mining, and transportationinfrastructure like roads (Turner II et al. 1990). Theimpacts of roads and traffic on the naturalenvironment are numerous and may extend formany hundreds or even thousands of meters beyondthe road (Forman and Deblinger 2000). Theseimpacts include mortality of wildlife due tocollisions with vehicles (Groot Bruinderink andHazebroek 1996, Huijser et al. 2009), pollution ofsoil and air (Bernhardt-Romermann et al. 2006,Bignal et al. 2007), modification of wildlifebehavior in response to noise (Parris et al. 2009,Parris and Schneider 2009), creation of barriers towildlife movement (Merriam et al. 1989, Kerth andMelber 2009), and establishment of dispersalconduits for some plant and animal species(Parendes and Jones 2000, Brown et al. 2006). Muchattention has focused on the rate, magnitude, andfinancial cost of mortality of wildlife due tocollisions with vehicles, particularly in Europe andNorth America where a collision with a large animalimpacts human welfare (e.g., Groot Bruinderink andHazebroek 1996, Huijser et al. 2009). However,factors such as the removal of roadkill by scavengers

Experimental study designs to improve the evaluation of road mitigation measures for wildlife.

An experimental approach to road mitigation that maximizes inferential power is essential to ensure that mitigation is both ecologically-effective and cost-effective. Here, we set out the need for and standards of using an experimental approach to road mitigation, in order to improve knowledge of the influence of mitigation measures on wildlife populations. We point out two key areas that need to be considered when conducting mitigation experiments. First, researchers need to get involved at the earliest stage of the road or mitigation project to ensure the necessary planning and funds are available for conducting a high quality experiment. Second, experimentation will generate new knowledge about the parameters that influence mitigation effectiveness, which ultimately allows better prediction for future road mitigation projects. We identify seven key questions about mitigation structures (i.e., wildlife crossing structures and fencing) that remain largely or entirely unanswered at the population-level: (1) Does a given crossing structure work? What type and size of crossing structures should we use? (2) How many crossing structures should we build? (3) Is it more effective to install a small number of large-sized crossing structures or a large number of small-sized crossing structures? (4) How much barrier fencing is needed for a given length of road? (5) Do we need funnel fencing to lead animals to crossing structures, and how long does such fencing have to be? (6) How should we manage/manipulate the environment in the area around the crossing structures and fencing? (7) Where should we place crossing structures and barrier fencing? We provide experimental approaches to answering each of them using example Before-After-Control-Impact (BACI) study designs for two stages in the road/mitigation project where researchers may become involved: (1) at the beginning of a road/mitigation project, and (2) after the mitigation has been constructed; highlighting real case studies when available.

How effective is road mitigation at reducing road-kill? A meta-analysis.

Road traffic kills hundreds of millions of animals every year, posing a critical threat to the populations of many species. To address this problem there are more than forty types of road mitigation measures available that aim to reduce wildlife mortality on roads (road-kill). For road planners, deciding on what mitigation method to use has been problematic because there is little good information about the relative effectiveness of these measures in reducing road-kill, and the costs of these measures vary greatly. We conducted a meta-analysis using data from 50 studies that quantified the relationship between road-kill and a mitigation measure designed to reduce road-kill. Overall, mitigation measures reduce road-kill by 40% compared to controls. Fences, with or without crossing structures, reduce road-kill by 54%. We found no detectable effect on road-kill of crossing structures without fencing. We found that comparatively expensive mitigation measures reduce large mammal road-kill much more than inexpensive measures. For example, the combination of fencing and crossing structures led to an 83% reduction in road-kill of large mammals, compared to a 57% reduction for animal detection systems, and only a 1% for wildlife reflectors. We suggest that inexpensive measures such as reflectors should not be used until and unless their effectiveness is tested using a high-quality experimental approach. Our meta-analysis also highlights the fact that there are insufficient data to answer many of the most pressing questions that road planners ask about the effectiveness of road mitigation measures, such as whether other less common mitigation measures (e.g., measures to reduce traffic volume and/or speed) reduce road mortality, or to what extent the attributes of crossing structures and fences influence their effectiveness. To improve evaluations of mitigation effectiveness, studies should incorporate data collection before the mitigation is applied, and we recommend a minimum study duration of four years for Before-After, and a minimum of either four years or four sites for Before-After-Control-Impact designs.

Monitoring the use of road-crossing structures by arboreal marsupials: insights gained from motion-triggered cameras and passive integrated transponder (PIT) tags

Abstract Context. Wildlife crossing structures are installed to mitigate the impacts of roads on animal populations, yet little is known about some aspects of their success. Many studies have monitored the use of structures by wildlife, but studies that also incorporate individual identification methods can offer additional insights into their effectiveness. Aims. We monitored the use of wildlife crossing structures by arboreal marsupials along the Hume Freeway in south-eastern Australia to (1) determine the species using these structures and their frequency of crossing, (2) determine the number and demographic characteristics of individuals crossing, and (3) use the rate of crossing by individuals to infer the types of movement that occurred. Methods. We used motion-triggered cameras to monitor five canopy bridges and 15 glider pole arrays installed at 13 sites along the Hume Freeway. The five canopy bridges were also monitored with passive integrated transponder (PIT)-tag readers to identify the rate of use by individuals. Key results. Five species of arboreal marsupial were detected using canopy bridges and glider poles at 11 sites. Our analysis suggested that increasing the number and the distance between poles in a glider pole array reduced the rate of use by squirrel gliders. The PIT tag and camera footage revealed that the structures were used by adult males, adult females and juveniles, suggesting that all demographic groups are capable of using canopy bridges and glider poles. At two canopy bridges, multiple squirrel gliders and common brushtail possums crossed more than once per night. Conclusions. Given that previous studies have shown that the freeway is a barrier to movement, and that many of the species detected crossing are subject to road mortality, we conclude that canopy bridges and glider poles benefit arboreal marsupials by providing safe access to resources that would otherwise be inaccessible. Implications. Although the factors influencing crossing rate require further study, our analysis suggests that glider pole arrays with fewer poles placed closer together are likely to be more successful for squirrel gliders. The individual identification methods applied here offer insights that are not possible from measuring the rate of use alone and should be adopted in future monitoring studies.

Quantifying predation attempts on arboreal marsupials using wildlife crossing structures above a major road

We review eight years of monitoring data to quantify the number of predation attempts on arboreal marsupials using canopy bridges and glider poles across a major road in south-east Australia. We recorded 13 488 detections of arboreal marsupials on the structures, yet only a single (and unsuccessful) predation attempt was recorded.

Radio-collared squirrel glider (Petaurus norfolcensis) struck by vehicle and transported 500 km along freeway

Roadkill (the mortality of animals through wildlife–vehicle collisions) is one of the main impacts of roads on wildlife. Studies quantifying the location and rate of roadkill to identify ‘hot spots’ are often used to guide the location of mitigation efforts, such as fencing or wildlife crossing structures. However, sometimes quantifying rates of roadkill can be challenging, particularly for species that are small and difficult to detect. In our study, a squirrel glider that was trapped and radio-collared in north-east Victoria was found as roadkill more than 500 km away, suggesting that a vehicle struck the animal and carried the carcass away from the site of impact. Our observation is the first evidence that this occurs for squirrel gliders.

Development of nine polymorphic microsatellite loci in the squirrel glider (Petaurus norfolcensis)

We designed nine polymorphic markers for the squirrel glider (Petaurus norfolcensis), an arboreal marsupial in eastern Australia. These markers will assist in the management of isolated populations and the evaluation of wildlife corridors.

Correcting common misconceptions to inspire conservation action in urban environments: Urban Conservation

Abstract Despite repeated calls to action, proposals for urban conservation are often met with surprise or scepticism. There remains a pervasive narrative in policy, practice, and the public psyche that urban environments, although useful for engaging people with nature or providing ecosystem services, are of little conservation value. We argue that the tendency to overlook the conservation value of urban environments stems from misconceptions about the ability of native species to persist within cities and towns and that this, in turn, hinders effective conservation action. However, recent scientific evidence shows that these assumptions do not always hold. Although it is generally true that increasing the size, quality, and connectivity of habitat patches will improve the probability that a species can persist, the inverse is not that small, degraded, or fragmented habitats found in urban environments are worthless. In light of these findings we propose updated messages that guide and inspire researchers, practitioners, and decision makers to undertake conservation action in urban environments: consider small spaces, recognize unconventional habitats, test creative solutions, and use science to minimize the impacts of future urban development.

An evaluation of pipe traps for the capture of small arboreal mammals

Optimal wildlife survey techniques should maximise detectability or capture rates of target species and minimise potential harm to animals. We compared the effectiveness of Elliott and PVC pipe traps for the capture of small arboreal mammals in the Victorian Central Highlands and found that pipe traps were less effective at capturing small arboreal mammals than Elliott traps.