Bunny fight after separation for neutering. Boy and girl siblings

[kgsmiley85]

So I just adopted a boy and girl Flemish giant mix. 12 weeks old. Male was just neutered 4 days ago. They were separated by an xpen panel for a little over a week (as soon as the first sign of humping occurred according to the foster)
I just adopted them today and they snuggled on the ride home, hung out in their cardboard box and napped together, ate together, groomed each other. Peaceful normal interaction. As I'm going to bed a fight broke out. I didn't see how it started or anything. Had another pen set up thank goodness and immediately separated for the night. They were in a 4ft x 4ft pen, so not over crowded.
Any thoughts?
Do you think the boy still just needs some time from his recent neutering to get the testosterone out of his system? Just supervised playtime for a while?
My first and only other rabbit was a single so this is new to me on pairs other than all the reading I've done. But since they are super young siblings I didn't anticipate any problems.
Thoughts on why it happened and where I go from here?

The female won't be spayed for several months.

Thanks!

 

[Hyatt101]

Hmm... yes, i think you might be right about him just needing his space for a little bit. Try again, but give him some time. Hope all goes well!

 

[MyBabyHasPaws]

I wouldnt have them together again until I got her spayed. Supervised playtime is okay but I wouldnt house them together. Its my understanding that buns change smell when they get neutered/spayed and sometimes re-bonding is needed.

 

[Imbrium]

it can take weeks for the hormones to stop flowing through your newly-neutered boy; by the time that happens, the female will hit sexual maturity and want to pick fights with him (happens around 4 months for females). I'd keep them apart but near each other until after her surgery.

as a note, I believe it can take as much as a month after neutering for a male to no longer have any chance of impregnating a female and bunnies are induced ovulators so she can get pregnant the second she hits sexual maturity (which is right around the corner), so I wouldn't even do supervised together time - one hump and you could potentially have a knocked-up preteen that isn't ready to handle it.

making sure they don't have more opportunities to fight now will make the bonding process much easier later... if you can keep them in a similar set-up to what they had with the foster (just a pen panel separating them or cages beside each other) so they're used to the other bunny's smell, that can also make it easier to bond them later.