I have recently bought two female 3 year old bearded dragons which cohabitate however, when I take both bearded dragons outside the vivarium at the same time one of them becomes aggressive towards the other. I am unsure if to only take them out separately or if this behaviour will stop, as the previous owner said that there were no issues with aggressive behaviour. Any advice?
Very dangerous to have ANY TWO bearded dragons sharing the same viv even if it's a very big one (much larger than the standard 4ft L x 2ft W x 2ft T used to house ONE adult bearded dragon).
I know there are some who claim they have two adult females peacefully cohabitating in one viv , this is very rarely successful and nearly always ends in one dead or horribly maimed (tails, legs arms torn off).
PLEASE SEPARATE THE PAIR ASAP into their own vivs.
Never have both out together - they can move like lightning and it only takes seconds for one to kill the other.
Commenting to reinforce what is stated above.
SEPARATE THEM ASAP.
I think the fact you are seeing aggression outside of the enclosure is only solidifying that there is a clear dominance/submissive hierarchy already formed.
Both dragons need their own space. They are not meant to live together. Just because they aren't visibly fighting inside the viv does not mean they are fine and nothing is going on. There is mental abuse/stress that we cannot see, and one, if not both, has to live their life at the edge of their seat, always on guard of the other. They can never properly relax and let their guard down.
Some may claim they have had success with two in a vivarium, but again, just because they aren't biting each other doesn't mean they get along.
To place them together in any situation is risking the lives of your dragons. They might look like they are getting along to you but, one of them if not both, are very stressed out. It is coming to a head now and, one of them if not both are going to get hurt, maimed or, worse very soon!
It is time for another viv now, not in two weeks but now.
Here's what can happen if you don't!
These two lived together for two years until in an instant one of them snapped!
You will see a big difference in the way they act when you do! They will be much happier alone and, they will love you for it!
Make sure the one that was attacked stays in the original viv and the other one goes into the new one. This keeps the stress down in an already stressful situation.