...any way to determine what kind? Lemon? Orange? Grapefruit? Lime? Other?
I mean apart from waiting years to see what fruit it will yield.
I'm in Australia so it isn't squirrels. I have a grapefruit tree in our yard but any windfall (or ground fall as someone has called it) is picked up and thrown in the bin and is several meters form the garden. Kids eat fruit in the yard - oranges and mandarins mainly.
Yes, I know about grafting trees. However there has to be original trees - from seeds. And consider the Granny Smith apple - a self seeded apple, mutation of the crab apple now used world wide for cookind