They are all the above. I will raise abandoned babies and hunt the big ones when in season. I have a simbiance with the two that eat out of my bird feeder behind the house. They eat the food out of that feeder only and leave the other feeders alone as long as they share with the birds and chipmonks and I get to watch the drama while washing dishes.
So Australia does not have squirrels...hmmm. Sounds like we need to send some over there. Everyone else has been sending their destructive species over here.
If you don't have a garden or feed birds there neat, all ours have died, they have come down with a mystery disease. Last year you couldn't walk five feet without seeing one, this year I have only seen one gray squirrel.