Resource agression?

Question
Hi Jill

I have recently adopted a rescue stafford bull terrier (about 7 months old and we have had him about a month). We have no info on his previous background. Basically we have been lucky and most of his bad behaviours such as stealing socks or shirts off the washing line are typical puppy things which we are working towards with slow but positive success. (He was neutered almost 2 weeks ago, i basically had him vaccinated and then straight in for his operation so his buster coller came off on Tuesday just gone)
The only concern I have is regarding his toys and chews, mainly toys (Food i can give or takeaway with no problems). Basically he will not let go of his toys unless i give him a treat. But he keeps putting the toys in my hand when i sit in the garden with him.

If i do hold the toy he pulls and growls however he is in a play bow position and there is no other sign of aggression (lip curling, attempts to bite etc -although he has caught me by accident when he had hold of his training lead and went for a better grip and my thumb was in the way, he didn't cause me any injury it just twanged for a second) and the growl doesn't seem threatening (like my other dog who growls at strangers but actually just makes the noise and loves to go greet people, she just growls for some reason but it sounds real) If i let go he shakes it about a bit and then puts it back in my hand but never lets go. I have no chance of winning a tug of war with him as his jaws are like vices and I have read mixed info on the pros and cons of playing tug of war. I would love to play this with him but have refrained so far just in case it is a bad idea.

Is this just trying to play or is it genuine aggression and what options do i have either way?

Answer
Nature of the breed: lock on. Playing games that the dog "wins" because he "can" isn't a good idea.  The dog needs some work on "take it/leave it".  See the following from Dr. Ian Dunbar:
http://www.youtube.com/watch?v=ApIJV8oGphg&feature=related

This dog is NOT demonstrating resource guarding or any other sort of aggression.  He's just "winning".  He needs to learn that GIVING YOU the toy is more rewarding than keeping it.  Once you've worked with this technique randomly over approximately 36 trials, he should "leave it" happily.  Always keep the toy at the end of any "game".  Avoid "tug of war" per se without understanding it.  See these links:
http://www.dogstardaily.com/videos/tug-war-0
http://www.dogstardaily.com/videos/find-tug-toy-0

All training must be positive reinforcement only.  See Dr. Ian Dunbar's free video course here:
http://www.youtube.com/watch?v=Hv38ornzzuQ

Proceed slowly, one behavior at a time, with calm, consistent approach.