Factors associated with road mortality of the
Bare-Nosed Wombat (Vombatus ursinus)
in the Nowendoc “hot spot” region

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by Natasha Crook

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Summary

Road mortality has reduced many wildlife populations globally. Understanding animal ecology in road-affected environments has become a high priority in order to develop effective mitigation strategies. Thunderbolts Way is a road located within the Northern Tablelands, New South Wales and has been identified as a hotspot for road deaths of the bare-nosed wombat (Vombatus ursinus). Although it is known that wombat populations throughout NSW have been reduced because of high road mortality, an understanding of the particular characteristics of wombat populations within hotspots is limited. Increasing such understanding could help increase the effectiveness of measures to mitigate wombat road kill within hotspots.

This study aimed to assess a wombat population within a hotspot location and to evaluate if existing road structures can be used as effective mitigation measure to reduce wombat road mortality. The study examined aspects of wombat ecology, specifically, burrows density and occupancy, and assessed the use of drainage culverts by wombats. Should it be shown that wombats do use such culverts, their appropriate installation could provide a cost effective and safe road-crossing for wombats.

The two hypotheses tested in this study which aimed to better understand wombat ecology were: that burrow density would be high in areas of high forest cover and burrow occupancy would be low compared with wombat occurrence at burrows locations. The hypothesis that was tested with respect to mitigation measures was that wombats would use the available culverts to cross the road.

The wombat ecology hypotheses were tested using two methods: distance sampling to determine wombat burrow density; and camera trapping using the detection/non-detection method to determine occupancy estimations of burrows and wombat presence. Culvert use was assesses by using cameras and tracks, as well as the detection/non-detection method.

The wombat ecology hypotheses were tested using two methods: distance sampling to determine wombat burrow density; and camera trapping using the detection/non-detection method to determine occupancy estimations of burrows and wombat presence. Culvert use was assesses by using cameras and tracks, as well as the detection/non-detection method.

The high burrow densities, determined by distance sampling, and study results that show based on the averaged-model estimate from camera-trapping which show that half of the burrows are being occupied, suggests that there is a high wombat population in the areas around Thunderbolts Way. The indications are that wombat habitat preference found in the habitat characteristics along Thunderbolts Way have resulted in the road being a hotspot for wombat road mortality.

Drainage culverts look promising as a tool for providing wombats with a safe passage across the road. A further benefit of this study is the finding that the detection/non-detection method can be used as a monitoring tool.

Further studies are required to determine: if road mortality does in fact have a significant negative impact on wombat populations; and whether culverts can be made more attractive for wombat use. Such studies would further increase knowledge of wombat ecology in hotspot locations and facilitate the development of effective mitigation strategies to reduce wombat road mortality.


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