Have you ever driven past special wildlife road crossings and wondered if they really work?
Key Points:
- New study from Southern Cross University provides evidence that road underpasses are used by wildlife to cross safely
- It is the first long-term study of underpasses in Australia and focused on two locations in northern NSW.
- He found that some mammals used underpasses more than once a week
There is new evidence to suggest they are effective, based on the first long-term study of road underpasses in Australia.
The research from Southern Cross University (SCU) was published in the journal Ecology and Evolution and was based on a two-year study of underpasses located on the north central coast of New South Wales.
During this time, wildlife cameras spotted nearly 5,000 medium and large mammals and goannas using road underpasses in Port Macquarie and Grafton.
The researchers studied 12 underpasses in these two areas, five under the Oxley Highway in Port Macquarie and seven under the Pacific Highway south of Grafton, comparing animal camera trap detections in the underpasses with those at forest sites nearby
A koala is caught on camera using a motorway underpass on the central north coast. (Provided by: Southern Cross University)
Lead researcher SCU Associate Professor Ross Goldingay said the results were encouraging.
“Over 4,800 detections were made – that number was quite staggering,” he said.
“These crossing rates suggest that the animals used the underpasses to forage on both sides of the freeways.”
Associate Professor Goldingay said certain species such as eastern gray kangaroos, swamp wallabies, red-necked wallabies, red-necked pademelons and lace monitors cross some underpasses more than once a week.
A dedicated wildlife underpass in Port Macquarie where there have been regular animal sightings. (Provided by: Southern Cross University)
“We actually have quite a bit of animal traffic going through these underpasses, particularly in Port Macquarie … there’s a wetter type of forest, so there seems to be a greater abundance of animals,” he said.
“We were getting eastern gray kangaroos and swamp wallabies moving through two to four times a week and other species, including the red-necked pademelon, were coming through once every two weeks, so quite often.
“At Grafton we have very high use of a couple of echidna underpasses and another little wallaby called the rufous bettong, which is actually a NSW-listed threatened species.”
Concerns of “prey trap” have been ruled out.
The study also allayed concerns that the underpasses could become a “prey trap” used by introduced wild pests and that animals could become trapped in the relatively confined area.
The reddish bettong is a small, nocturnal marsupial species that has been seen using underground passages. (Provided: Mt Rothwell)
“We looked at it in detail, as there have been a couple of other short-term studies where they’ve had frequent cases of foxes in a few underpasses, and in one case in Western Australia that coincided with a decline in bandicoots using this particular. underpass,” Professor Goldingay.
“Because we had more underground passages and a longer period for this study, we were able to look at it in more detail than anyone before.”
Professor Goldingay said predators spotted in the underpasses included the introduced red fox, wild cat and dingo.
“What we found was that feral cats were very rare at both sites. We had dingoes at both sites, but they were not very common in the underpasses,” he said.
“The red fox is the main concern, particularly in Port Macquarie. Of the five underpasses there were three that were used relatively frequently.
“However, fox activity coincided less than expected with the activity of higher-risk mammals and it appeared that potential prey may have avoided using the underpasses when foxes were nearby.”
Caution is still required
A combined wildlife and drainage underpass in Grafton. (Provided by: Southern Cross University)
Despite the positive results of the study, Professor Goldingay said any expansion of road networks in Australia still needed to be done with caution.
“Australia’s wildlife species are increasingly threatened with extinction by habitat clearing and fragmentation,” he said.
“One of the main causes of this is the expansion of our road network, particularly the upgrading and doubling of major roads.
“Underpasses are a useful generic tool for allowing wildlife to move through landscapes with roads. But not all land-dwelling wildlife species will find underpasses to their liking, but so far, many do.”