I have been pondering this since I read your reply, TubeDriver. It's hard to explain Jasper's attitude. He will run if chased, but he seems to think he's some sort of Rottweiler squirrel. (Don't get me wrong, I'm quite fond of Rottie's, but my squirrel needs to understand he weighs about a pound). I think I trained him to believe he was the big guy in charge when I made all the animals stay away from his cage, trying to keep separation between him and the pets. It was impossible to actually keep that separation, but I was able to train the cats and dogs to leave his cage alone. So he thinks he's hot stuff, and he's extremely possessive of his cage.
I've spent hours in the back yard this past week spraying the cats and dogs with the hose when they get too close to his cage. He's burying nuts, and the dogs are going around behind and picking them up, and he's getting seriously TICKED. At one point, when he was outside with my daughter and our puppies (3 months old), he jumped on the puppy's back because she wouldn't go away. The puppy screamed and ran and I'm sure we could have made a lot of money on AFV. My husband thinks I should spray Jasper because he's the one who needs to learn to run (like you said)-- but I'm afraid if I do that he'll never come back down to his cage.
He's spending more and more time in the trees but still comes down before dusk to eat and he sleeps in his cage every night (except the first night, little meanie.) He has a little girlfriend who has an approximately 12 week old juvenile with her, and he willingly shares his food with them. He is starting to 'wild up' and I hope we can get through this transition phase without any injuries. In the meantime, I'll continue to keep a close eye on everyone and keep my garden hose ready.
I'm already planning a different release spot, not in the middle of the back yard, for the next guys to go out to the trees. The good news is I think I've successfully scared my cats away from his cage, and him. They seriously hate being blasted with water.