In absence of a good strong wire fence maybe try deer netting, a black plastic mesh almost see through. Support with tposts & supplement with taller bamboo poles if you have them. Secure the bottoms, too. Electric fencing top & bottom string also works. You can purchase a white rope as sold for horses. Once they have been zapped they will learn to stay out.

Also alternate repellents every 2 weeks as an extra precaution to discourage any attempts to break through the fence. Tied to fence with panty hose or sprayed around. Anything strong smelling like bloodmeal, garlic, hot peppers, spearmint, Irish Spring soap, human or dog hair, etc. Some people have good results by walking their male dog around the perimeter to urinate on a regular basis.

Once you interrupt the feeding habits you can let up a bit, but it takes awhile to stop patterns and any break in the fence invites them back...