Thirty small holes were discovered yesterday morning in the two-metre high fence that encircles 485 hectares of the sanctuary.

The holes are believed to have been cut on Sunday night, and members of ACT Parks and Conversation believe that protesters of the controversial kangaroo cull may have been responsible.

Parks and Conservation director Daniel Iglesias said the area was commonly visited by foxes, with the fence the only thing keeping predators out.

Mr Iglesias said one fox could completely wipe out the group of 17 eastern bettongs.

Fox bait has been placed inside the sanctuary, and cameras will be used to monitor the area.

Mr Iglesias said that if foxes were detected, the entire group of eastern bettongs would be trapped and moved from the reserve for protection. He said he had no idea why the holes would have been cut, as most were too small for humans or kangaroos to fit through.

''If it was indeed done by protesters as part of the cull, it makes no sense, because these people are meant to have respect for animals and here they are being the cause of the reintroduction of the fox to a fox-free area,'' Mr Iglesias said.

''These animals [eastern bettongs] are extremely sensitive to foxes … they won't survive a fox attack, they'll all go in the one night,'' he said.

''There's no excuse for it.''

A section of fence at the Kama Nature Reserve was also damaged at the weekend, and glue has been used on 20 gate locks to render them useless.

Animal Liberation ACT issued a statement yesterday denying any knowledge of the vandalism, and saying it was not responsible.

''In regards to the reported property damage at Mulligan's Flat, Animal Liberation ACT has no knowledge of how this was done or indeed who did it,'' a spokeswoman said.

''There are many angry individuals out there who see the government as refusing to enter into fair and reasonable dialogue with kangaroo supporters … and as such, individuals will then express this anger and frustration in their own particular way,'' she said.

''If governments and scientists alike refuse to consider the intrinsic sentience of our wildlife, in particular the eastern grey kangaroo, then people who have sworn to protect the kangaroos will fight back.''

Mr Iglesias said similar vandalism happened during the cull in the ACT last year.

He said the government would use the reserve's remote cameras to try and identify who was responsible.

The vandalism has been referred to ACT Policing, and Mr Iglesias has urged any nearby residents with information to pass them on.