That doesn't look like they were munching. It looks like what we call a rub.
When a deers velvet is starting to dry they rub and thrash their antlers
on trees and brush. In preperation for the breeding battles to come.
Yeah that's for sure a rub. Did they work the ground around the tree also?
They'll eat your fruit trees to a nub and especially seem to like cherry leaves. You'll need at least 8 ft fencing to keep them out.
Don't know if Australia has a similar feature but the Canadian First Nations have what rights guaranteeing a licence which means they can shoot whatever and whenever deer they want for food purposes. They've become the unofficial pest control guys in more than a few places. Might be a consideration.
Here in California I can get a depredation permit from fish and game to shoot wild pigs out of my grain fields. The permit allows me to take as many as I want and I can spotlight them at night when they are out doing their damage. All you have to do is show a game warden the damage that they are causing. I can utilize the meat anyway I want; use it myself, give it away or whatever, I just can't sell the meat.