"The threatened giant barred frog is one of the animals being monitored, as it lives in waterways under the highway between Port Macquarie and Eungai," Ms Sisson said.

"They are still using the waterways despite the fact streamside vegetation was cleared during construction, which was a potential barrier to the safe movement of the frogs.

"Re-vegetation of these waterways is a priority for Roads and Maritime, which has had a long commitment to ensuring the best welfare outcomes for wildlife during highway upgrades."

Dr Radika Michniewicz of Niche Environment and Heritage, the consultancy undertaking the monitoring, said as frogs are caught, they are tagged so they can be identified when recaptured.

"Several frogs have been recaptured on opposite sides of the highway, showing they had used the waterway to travel from one side to the other," she said.

"Koalas are using underpasses designed and built to provide safe passage for wildlife, while the Spotted-tailed Quoll has been monitored using a specially-modified drainage culvert."

Dr Michniewicz said nest boxes installed near the highway by Roads and Maritime to provide roosting and nesting habitats are also showing regular use by target animals, including the threatened Yellow-bellied Glider, Squirrel Glider and Brush-tailed Phascogale.

"Surveys have also found several different glider species are using the glider poles installed by Roads and Maritime to help them cross the busy roadway," Dr Michniewicz said.

Ms Sisson said it's vital that wildlife can move freely to other areas to access food, water and mates so when highways are upgraded or built, opportunities are provided for wildlife to cross the road safely.

"Roads and Maritime is installing similar measures on the Woolgoolga to Ballina section of the Pacific Highway upgrade, as part of the project's compliance for the management of threatened species," she said.