Here is a pretty good video that goes over the different noises that sugar gliders make.
Personally, I have only heard my sugar gliders bark, crab, and "sneeze". My sugar gliders bark on a daily basis, right before they tuck themselves in for bed around seven in the morning (they are nocturnal). Based on their habits and personalities, I think that it is Tinki barking at Telly and it is because she is telling him to calm down and go to bed. I have only heard Telly crab and he only did it on the day that we brought him home. I think that he crabbed at my sister and I because he was scared and wanted to portray himself as a vicious giant, rather than a cute little fur-ball. Since sugar gliders are so tiny and really do not have a way of defending themselves against predators, they use crabbing to try to scare the predator away from them. When sugar gliders crab they make themselves look bigger than they actually are, expose their teeth, and make a very loud, distinctive cry that can actually be very intimidating.
Here is a video that my sister and I found on YouTube and watched when Telly crabbed, and we had no idea what he was doing or why he was doing it. It was a good reference video to learn that crabbing is a natural and normal sugar glider noise.
