Vulnerable species on Kangaroo Island are bouncing back thanks to a 380-hectare "predator-free" enclosure erected by the Australian Wildlife Conservancy.

It has been five years since the Western River Refuge was enclosed by a cat-proof fence.

The endangered Kangaroo Island dunnart has seen a resurgence thanks to the Western River Refuge. (Supplied: Natural Resources Kangaroo Island)

Australian Wildlife Conservancy principal ecologist Pat Hodgens is surprised at how well vulnerable species within the refuge are faring.

He estimated species such as the Kangaroo Island dunnart have increased in numbers by 90-100 per cent.

Mr Hodgens was unable to provide an accurate pre-bush fire estimate as to the exact numbers and has previously said the dunnart was notoriously difficult to survey because of its size and shy temperament.

"So the dunnart has fared a lot better than I think a lot of people thought [they would] … especially me, six years ago," he said.

"There are still dunnarts outside of the fence in pretty good numbers, but we are definitely seeing a steady consistently higher activity level of dunnarts within the fence versus the outside."

Western whipbirds have been spotted at the Western River Refuge for the first time in years.  (Supplied: Brad Leue/Australian Wildlife Conservancy)

Experts were shocked at the reappearance of birds such as the western whipbird in the wake of the devastating fires.

But Mr Hodgens said its numbers have also jumped by roughly 100 per cent.

"The western whipbird and also the Bassian thrush … these birds are also really predated upon by feral cats," he said.

"We didn't have any of those birds living within the feral cat exclusion fence at the time of construction, but they've found their way back there."

Good timing

Mr Hodgens said the Western River Refuge project was intended to be an experiment.

But in the wake of the bushfires the project went from an experiment to "a rescue mission".