It’s hard for me to tell exactly where you’re at in your bonding here. Are they together full time right now? What steps did you take in the beginning? Are they both altered?

A week ago? That’s awfully short, it’s generally recommended that you let a new rabbit settle in a little bit before you toss him in with a new rabbit. It’s no wonder then that he acts so frightened. This is a lot of stress all at once. The way this process has gone might be a little different if you’d waited.

I’d say that they’re not fully bonded yet and they’re not ready to be together unsupervised. You don’t necessarily have to like, stand over them all day, but you should at least be like, in the house. If you’re going to be out for any amount of time I’d separate them, because you could have a big nasty fight while you’re away and that could have adverse affects on the bond. That means sleeping in the same room as them too so you can quickly break up fights, especially since they usually fight at night.

Ideally you won’t have a whole lot more of this, and new bun’s personality won’t be any different once he’s settled in and things will continue to go well for you. Just a few fights at night is really good, assuming that the new bunny isn’t behaving drastically different than he usually does out of fear, but just in case that’s what’s happening, I think lots and lots and lots of supervision is the way to go. But hopefully you won’t have more than a few days of this.