Highway effects varied across native mammal species in a conservation reserve

What the study found: A highway through a conservation reserve in north-east New South Wales was associated with different responses among eight native mammal species. The strongest occupancy response was seen in the vulnerable parma wallaby, while the mountain brushtail possum was detected more often near the highway than farther into the forest.

Why the authors say this matters: The authors conclude that an occupancy approach can be used to investigate wildlife responses to roads, and they say further studies are needed to better understand whether major roads through conservation reserves adversely influence wildlife populations.

What the researchers tested: The researchers used camera trapping over 17 months at sites along a highway and at sites 0.5–10 km away along service roads through adjoining forest. They examined whether eight native mammal species were influenced by the highway, using occupancy and detection probability.

What worked and what didn't: For the vulnerable parma wallaby, occupancy increased from 0.5 at highway sites to 0.96 at sites more than 3 km into the forest interior. For the vulnerable long-nosed potoroo and the swamp wallaby, detection probability increased by 10% from the highway to the forest interior, but season or recent wildfire caused larger changes in detection. The mountain brushtail possum showed the opposite pattern, with higher detection near the highway than in the forest interior, and the endangered spotted-tailed quoll was too infrequently detected to assess its highway response adequately.

What to keep in mind: The abstract does not provide a direct conclusion that the highway harmed all species, and it notes that some species were affected by other factors such as season and recent wildfire. The spotted-tailed quoll was detected at many sites, but not often enough for a clear response estimate.

Key points

• The study examined eight native mammal species along a highway in a conservation reserve in north-east New South Wales.
• Parma wallaby occupancy was lowest at highway sites and highest more than 3 km into the forest interior.
• Long-nosed potoroo and swamp wallaby detection probability rose by about 10% from the highway to the forest interior.
• Mountain brushtail possums were detected more often near the highway than in the forest interior.
• Spotted-tailed quolls were detected at 80% of sites, but not often enough for a clear highway-response estimate.