Possible to have wire mesh fencing plus a couple live wires for wild animals?
There are standard electric fence insulators for T-posts.

Some only go on one side of the post - others have more options.

If you cannot get adequate spacing from the T-posts to prevent shorting, or cannot find insulators that fit with the mesh, you can run a separate electric fence a short distance outside the mesh, on T-posts or on fiberglass posts. With a tightly tensioned mesh and electric fence wire/string/tape little spacing is needed - but if the current mesh fence is loose, it's probably going to be easier to run a second fence, which can generally get away with fewer posts.

Electric fences in the woods require regular inspections to be effective. Branches and trees fall on them and short them out, break them, or hold them to the ground.