Context . The presence of large mammals on roads poses a serious risk to both the animals and motorists if collisions with vehicles occur. Fencing roads can reduce this risk, and it also limits the landscape-scale movements of animals. By also constructing fauna underpasses it may be possible to avoid collisions with vehicles, while, at the same time, allowing the natural movement of animals across the landscape.
Aims . We aimed to determine whether western grey kangaroos (Macropus fulignosus) would use fauna underpasses and to determine how this may affect their home range.
Methods . We used motion-activated infrared cameras to monitor the use of one large 8 × 3 m arched underpass and two 0.9-m-diameter fauna underpasses over 342 days between March 2011 and March 2012. The underpasses were situated between reserves separated by a four-lane fenced highway, with one reserve surrounded by residential properties. At the same time, 20 kangaroos (10 males and 10 females) were radio-tracked to determine the size of their home range and to test whether the animals incorporated the fauna underpasses into their daily movements.
Key results . The large fauna underpass was used 3116 times by individual kangaroos in groups of up to 21 animals, whereas the two smaller underpasses were used only twice. In total, 14 of the 20 radio-collared kangaroos used the large underpass over the course of the study, but underpass use did not affect home-range size. Kangaroos that did not use the underpass had a significantly higher proportion of their home range on residential properties surrounding one of the reserves than did those kangaroos that used the underpass.
Conclusions . The use of the underpass did not affect the size of the home range of the kangaroos, but it allowed the kangaroos to access grazing areas that would have been otherwise inaccessible. Fauna underpasses allow the safe passage of kangaroos between isolated remnant vegetation patches and may reduce significantly the risks posed to motorists and kangaroos from collisions.
Implications . Fencing roads and constructing fauna underpasses is a viable solution to reducing some of the problems of managing large kangaroos in peri-urban areas.