It found there were at least 100 living in the wild, the highest number recorded for the colony since counting began, according to NSW Environment Minister Gabrielle Upton.

Brush-tailed rock-wallaby numbers at Jenolan crashed to about 12 wallabies in 1999 before a monitoring program to help save the species was implemented and fox control measures were introduced.

The monitoring and fox control program are now part of the NSW Government’s $100 million Saving our Species program.

“This is a major Saving our Species success story – this is the highest number of wallabies recorded at the site since surveys started at Jenolan Caves mid-last century,” Ms Upton said.

“There has been an 80 per cent increase in the Jenolan Caves colony over the past two decades.” 

The Jenolan Caves’ brush-tailed rock-wallabies are surveyed twice a year, where the animals are caught, weighed and tagged.

Office of Environment and Heritage senior threatened species officer Deb Ashworth said rock-wallabies were commonly sighted at the caves in the early 1900s in areas like the Grand Arch and Devil’s Coach House, but disappeared from the area from mid-last century.

“Animals were initially placed into a predator-free enclosure and allowed to breed until they reached a level where the enclosure could be opened up,” she said. 

“The colony has become a great success story where their numbers are now at record levels and their range has expanded since opening the enclosure with ongoing fox control. We now see them back on the Grand Arch.” 

The latest survey results found 12 wallabies not previously recorded.

The surveys also recorded four quolls, another threatened species.