Nice post Tiakristin3
I'd like to just say gliders won't self mutilate from simply being a lone glider. Self mutilation happens when the glider is experiencing pain and tries to remove the source of the pain. It is not a sign of loneliness or depression. It's a common misconception and I once thought the same thing.
Barking happens for many reasons. many many reasons, and sometimes for reasons we don't understand yet.
Calling a mate, alerting there is a cage escape, loud noise startled them, the moon, in heat, hears something we can't hear, check in to see where the others in their colony are, barometric pressure change, a storm coming, attention seeking, demanding treats from the human, sometimes they just bark cause they can.
It's a normal verbal communication for gliders. Nothing to be concerned about it's just how they talk. If it were simply because of loneliness gliders in colonies wouldn't bark. It's their language how they communicate to each other and sometimes us too.
I have single intact 8 month old male, who barked at me last week, in a different tone, it was deeper than his usual bark. I even said that to him, whats wrong buddy you sound different tonight.... well the next morning I found out what he was telling me.
HE was not happy with me because I forgot to put his food plate in his cage. He was telling me "MOM WHERES MY DINNER" " GET MY FOOD!" "MOOOOOOOOM"
first time in 2 years my feeding routine got interrupted, all the other cages got their plates and somehow I missed his cage. I found his plate, full of food on the kitchen counter the next morning afterr I tried collecting dirty plates from the cages and didn't find his.
He was fine, but he tried to tell me I skipped him and I didn't understand him.
Don't stress about getting a cage mate till your ready, it can be a lot of work getting two gliders together. Introductions can be stressful to say the least. In the mean time, research introductions, how to prepare the gliders for their introductions. Research what all you will need as far as another cage etc for the second glider. Ask people who have done some introductions, what methods they used, was the intro successful, did the gliders get a long long term or did they have to be separated... It can be a big undertaking, so prepare for it in advance.
I do agree with getting him neutered, then giving him a month or two for his hormones to drop after the neuter before any intro.
I don't feel there is ANY reason you need to wait until he is 1 or 2 years old. Gliders can be introduced to another at any age. By any reason I mean in regards to the glider.
If YOU have reasons like, you can't get him neutered yet, or can't afford a cage mate, a 2nd cage, a 2nd wheel, a 2nd cage set, a 2nd bonding bag those are valid reasons to wait.
Congrats on your new baby, sounds like your doing just fine with him and give him lots of attention, and lots of your time.