New evidence suggests that road underpasses are actually quite effective in protecting vulnerable Australian wildlife.
The evidence comes from Southern Cross University (SCU) in the first long-term study of road underpasses in Australia.
New research explored whether highway underpasses are used by animals to cross roads safely and if there were unknown dangers to funnelling animals through a confined space where it could be easier for predators.
The research was published in the journal Ecology and Evolution, based on a study of underpasses in north-east New South Wales.
Wildlife cameras were used to monitor 12 underpasses for more than two years, five under the Oxley Highway at Port Macquarie and seven under the Pacific Highway south of Grafton.
The researchers were surprised by the unexpected number of animals that were using the underpasses.
“More than 4,800 detections were made; that number was quite astounding,” said Ross Goldingay, the lead researcher and SCU Lecturer in Wildlife Conservation and Biology.
“These crossing rates suggests animals used the underpasses to forage on both side of the freeways.”
The footage gathered showed underpasses were crossed more than once a week by species such as eastern grey kangaroos, swamp wallabies, red-necked wallabies, red-necked pademelons and lace monitors.
The study also addressed concerns that the underpasses could be a “prey-trap” for these animals.
“What we found was feral cats were very rare at both sites. We did have dingoes at both sites, but they weren’t very frequent in the underpasses,” said Professor Goldingay.
He said the red fox is the main concern, especially in Port Macquarie, where three of the five underpasses there were used by foxes.
“However, the fox activity coincided less than expected with the activity of the mammals most at risk and it seemed potential prey were possibly avoiding using the underpasses when foxes were about,” he said.
Despite finding these positive results, Professor Goldingay says caution needs to be exercised with any road network expansions.
“Australia’s wildlife species are increasingly threatened with extinction by habitat clearing and fragmentation,” he said.
“One leading cause of this is the expansion of our road network, particularly the upgrade and duplication of major highways.
“Underpasses are a useful generic tool to enable wildlife to move across landscapes with roads.
“But not all ground-dwelling species of wildlife will find underpasses to their liking but so far, many do.”