I have had my current glider, Lilly for almost 2 years and she is 5 years old now (I adopted her from a friend who could no longer care for her). A new coworker of mine just happens to be a sugar glider owner and he and his wife breed their gliders. I have been wanting to get a new one and I decided to get one now since their gliders just had a baby. I will be getting her in a week.
I have read a lot about people bonding with their new gliders, but I can't find much on introducing gliders to each other. Lilly is a dominant personality who expects to get her way, when she doesn't like my boyfriend and I talking she crabs and though, she doesn't always get what she wants, she always tells us. She is also aware that our 55 lb dog is afraid of her and will purposefully scare the dog. My new baby is much more passive and is minimally vocal. I am unsure how she will change as she becomes older and less attached to her parents (she is currently being weaned from them).
I am getting a new cage, which I hope will prevent territorial behaviors. The new cage is much larger and i can put the old cage inside of it. Should I put the small one in the big one and have one in the small cage and one in the large cage for a few days for them to get to know each other?
Also, I have heard putting them in a clean, empty bathtub is a good way to introduce them. What do you guys think?
Any other tips on bonding two gliders in general, especially ones with a significant age and personality differences?

cage must be SEPARATED at the start, gliders that can touch threw bars can get seriously hurt in a fight threw bars.

many sites with introduction procedures, many steps are very important.

Error, missing URL. /

Ok no need to put the small cage IN the other cage, that may actually create more problems and territorial issues even with females. Please make sure the joey is at least 9-12 weeks out of pouch before they separate from the parents to ensure the joeys are fully weened and are going to the bathroom on their own with out the parents stimulating them.

As Byk mentioned cages need to be at least 12 inches apart. Tails average from stumps to 8 inches long, they do stick out between the bars, their arm reach is about 1-2 inches through the bars so no closer than 12 inches.

The most common introduction method.... The new glider needs a wellness exam and fecal test, then a 2nd fecal test 30 days later. Two are done because some parasites don't show up on the first fecal test and are dormant at some stages of it's cycle.

If it's an intact male, a neuter as well.

The gliders live in separate cages no closer than 12 inches apart.

Over the next month you do scent swapping. Most people take the dirty pouch out of on cage and without washing it put it in the other cage. Then take that gliders dirty pouch and give it to the first cage. N swap them back n for every couple of days. Or you can use fleece squares and put them in the pouches and swap them back n forth. This helps get each others scents on the gliders in the opposite cage without them coming into direct contact with each other.

After the 2nd fecal clears you are free to do an introduction. If the fecal doesn't clear you need to wait until the glider is medicated and has clean fecals other wise the other glider will also get the parasite.

The intro in bathtub
yes, many use this method for a few reasons. It's a neutral smelling space that doesn't smell like either glider. It's easier access to the gliders for you if they ball up and fight, It's a semi contained space that isn't to big so the gliders eventually have to interact with each other. ( if you use a shower curtain flip it up over the shower curtain rod so they have to stay in the tub and cant climb )

What you do is place one pouch at one end of the tub with the opening facing the middle of the tub, put some treats in the middle then the other pouch at the other end of the tub facing the middle.

Once they all come out of their pouches ( they may need a nudge to come out ) remove their dirty pouches and let them interact with each other. If they aren't balling up ( and you will know it if they are ) and are getting along place a clean sleep pouch in the tub and let them all go in it.

Then monitor them for a while in the pouch. Manipulate the bottom of the pouch so they keep rubbing on each other to settle down this will help mingle their scents and the new glider will be accepted as part of the existing gliders colony easier.

Continue to monitor them In the cage for the next couple weeks to ensure they will get along long term. In that time use at least 2 feeding plates so you don't have any food aggression isses if they all eat well together you can go back to one plate or however you normally do it.

IF they don't get along, or ball up, separate them put them back in their original cages and continue scent swapping and up it to every day. Give it another week or two then try an intro again.

One essential thing to remember is for you to be as calm and relaxed as possible no matter what method you use. If you are nervous the gliders will be too and that does not help with intro's.

This is ONLY one method people use to do introductions but it is a good one for people that have never done one before.

Im going to make a separate post to address a couple other things to keep in mind

There is going to be a considerable size difference between a newly weened joey and a mature glider. This puts the joey at a very real disadvantage and it can't defend itself if the older glider goes after it. So you will have to intervene very quickly and separate them if that happens.

Normally we suggest waiting to intro's until the joey has grown a little more and can defend itself better.

However, having said that... I just introduced a 14 week old joey to a colony of 3, 2 of the gliders in the colony are at least 4 times her size, the other one is very close to her size. The intro took all of 5 minutes and they all get along famously despite her being so young and so little compared to the two. But keep in mind, I've had my gliders a long time and I knew where the joey would fit best, and the joey was born here.

This ISN'T always the case. Every situation is different so just because it was successful for me, doesn't mean it will be that easy for you. And it wasn't my first introduction.

Have a fleece square or pouch you can put on your hand to protect yourself if you have to separate them. You will get get bit and scratched.

Make sure to trim both gliders nails before the intro!!

Order some vetericyn vf BEFORE the intro so you have it on hand if either of them suffers a scratch or worse. https://www.amazon.com/Vetericyn-Wound-Skin-Care-Spray/dp/B006UJGZNG It's safe to spray directly on the eyes and face and any wound a glider may have. It's also safe if they ingest it from normal grooming.

Being prepared for the worst case scenario is important. The vetericyn is a good thing to keep on hand even if you aren't doing intro's I'm a firm believer that every glider owner should have some.

After the intro, keep the smaller cage. It may be needed down the road if the gliders ever need separated for ANY reason, hospital cage, travel cage etc... I have donated and given away so many small cages because people don't have one when they need it.

There are other methods as I said, some don't do any scent swapping instead they do a "cold intro" which simply means they just put the gliders together in a pouch and see what happens. This is usually done by people very confident and that have done numerous introductions and know what to look for. And they don't mind reaching blindly into a pouch of fighting gliders to pull one out.... sometimes they work sometimes they don't.

Other times when you know for a fact the new glider is healthy, people have just put the new one in the cage with the current one. ( another form of cold intro )
Usually this is only done with lineaged gliders who are going to become a breeding pair. I've actually done this once, Under the guidance of my mentor ( a veteran owner for 20 some years) who gave me the female that we introduced to my male. She was here with me when it was done. She told just go put her in the cage, so I did. They acted like newly found love birds for about 20 min then acted like they have always been together. They've produced one joey and currently have another in pouch.

I would NOT SUGGEST a new owner to use this method with no other previous introduction experience. I've done a few different methods myself, I've had successful intro's and non successful intros. Take the safe route for your first time.

I just got a companion for my male sugar glider. My older one (Sherlock) will climb on Watsons cage and they will interact. I don't know if they are being mean to each other or not. Watson hisses and grabs at Sherlock, but when I take him away Watson will just sit their and keep hissing. Sherlock generally doesn't react much to Watson. I don't know what it means. Is hissing always hostile?