I'm guessing ground squirrels too. You can wrap the base of the tree with a bunch of wire. It may not do any good. But, it's worth a try. I'll never forget the day I brought my brand new truck home. There were the squirrels up in an apricot tree .. dropping their rejects onto my new truck. Where are you that you can grow oranges like that? Those oranges look like they should have been picked. cheryl o7o
p.s In this photo it looks like you have some leaf mold going on as well. In the shot.. upper, mid-right, leaf.