Cutting the carnage: wildlife usage of road culverts in north-eastern New South Wales
Taylor, BD, & Goldingay, RL 2003, Wildlife Research, vol. 30, pp. 529-537.
Culverts may allow animals to move safely between two habitats that have been separated by a road or other linear infrastructure. Culverts installed along the Brunswick Heads section of the Pacific Highway in New South Wales provide safe passage for local wildlife, most frequently wallabies, bandicoots and rodents. Surveys also detected the use of culverts by arboreal mammals such as koalas and possums. In contrast, frogs and reptiles experience less benefit from culverts than other animals as exclusion fencing is ineffective for funnelling small-bodied animals into the culvert. Additionally, vegetation structure in and around culverts seems to influence whether or not an animal uses a culvert structure.
Seventeen vertebrate species, including 12 mammals, were detected using the culverts in a survey conducted over two eight-day periods in Spring and Summer of 2000. As reported in other studies, of all the animals observed, wallabies, bandicoots and rodents were the most frequent users of the culverts. Furthermore, house mice and a number of unidentifiable small mammals, presumably Antechinus species, common dunnarts and/or common planigales, were also detected using the culverts commonly. The detection of arboreal mammals such as koalas, ringtail and brushtail possums in culverts provides further evidence that the instalment of culverts and exclusion fencing along roads is an effective means to provide safe passage for these animals and prevent road mortality. Among all the animal groups detected using the culvert, frogs and reptiles were the least frequently sighted. With a high number of frog road kills also recorded during the survey period, this suggests that culverts are not appropriately designed to address the movement and dispersal needs of these small animals. The authors attributed this finding to the ineffectiveness of exclusion fences in preventing frog thoroughfare as well as the lack of suitable vegetation and habitat furnishings such as rocks and logs in the culverts to make them appeal to reptiles and amphibians.
Although this study cannot confirm that road culverts result in a direct reduction of road mortality for wildlife, the findings suggest that many fauna species make use of culverts to avoid entering the road surface and this reduces their risk of mortality. The authors propose that culverts be adopted more widely in areas where roadkill is a conservation concern, but with design alterations to encourage use by small-bodied animals.
Summarised by Cherie Chan
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