Michael J. Harper

The use of nest boxes in urban natural vegetation remnants by vertebrate fauna

Nest boxes are routinely installed as a substitute for natural tree hollows to provide den and nest sites for a range of hollow-utilising fauna. We installed 120 nest boxes in 20 patches of indigenous vegetation (remnants) across the urban/suburban landscape of Melbourne, south-eastern Australia, and investigated their use by indigenous and exotic vertebrate species over a period of 12 months. Nest-box use was dominated by the common brushtail possum (Trichosurus vulpecula), the common ringtail possum (Pseudocheirus peregrinus) and the common myna (Acridotheres tristis), an aggressive introduced bird. We found that brushtail and ringtail possums utilised nest boxes all year round but more frequently in cooler months (May–August). Common mynas dominated nest-box use during spring/summer, potentially reducing the availability of this resource to indigenous species. We found evidence that the probability of a nest box being occupied by either species of possum was greater in remnants with abundant possum populations. Brushtail possums preferred thick-walled pine nest boxes over thin-walled plywood nest boxes, most likely owing to differences in their thermal insulation properties. Although considerable economic costs would be involved in using nest boxes as a long-term substitute for hollow-bearing trees, nest boxes may provide a temporary hollow resource until hollow-bearing trees are recruited in urban remnants.

Home range and den use of common brushtail possums (Trichosurus vulpecula) in urban forest remnants

The common brushtail possum (Trichosurus vulpecula) is an arboreal marsupial that has adapted well to urban landscapes. Fifteen adult possums (12 female, 3 male) caught in small patches of indigenous vegetation (remnants) in the south-east of metropolitan Melbourne were radio-tracked over a three-month period to investigate nocturnal behaviour and den use. Minimum convex polygon (100%) home-range estimates of both female (1.02 ± 0.28 ha) and male (1.19 ± 0.33 ha) urban brushtail possums trapped in urban forest remnants appear to be smaller than those previously reported for urban brushtail possums. All the brushtail possums foraged extensively in remnants but made repeated forays into adjacent residential areas. The use of few dens, by both female (2.21 ± 0.35 ha) and male (2.51 ± 1.45 ha) brushtail possums, in close proximity to their nocturnal ranges is similar to the behaviour of non-urban brushtail possums

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