Fixed, but male is hormonal and becoming agressive

[Momma Luvbun]

Ugghhh
I hoped this would pass quickly but it's just getting worse...
So the situation is my buns have been together for 2 years freerun house buns, with no issues. Very lovey in fact.
But this spring my boy is hormonal. He's been fixed for 3 years.
The first couple of days it was just nipping my little girls bum. This makes my girl get up and move somewhere else.
Then it progressed to chase and mount, and my girl is not having it by mounting him back.
This morning was going ok, untill chase began and neither was giving in and a tight circle they went.
All of a sudden a tuft of fur flew off my little girl so now I have my male in a square of his expen untill I figure out where to go from here. I can make the square larger, I can put it straight to separate a room or I can leave them be and hope it passes quickly.
I don't want anybun getting hurt

Thoughts please.

 

[JBun]

It could be spring fever. It's when the coming of spring causes an upsurge of hormonal behaviors like nest building and mounting. This can even happen in fixed rabbits. I have a spayed doe that would start trying to frantically build a nest with the come of spring. And increased dominance humping behavior in altered rabbits definitely can happen too.

Some other possibilities for sudden unusual changes of behavior like this, can be an underlying health problem or changes to the rabbits environment. When a rabbit becomes sick and is in pain or discomfort, it can cause them to act aggressively or exhibit other unusual behavior, resulting in them behaving in ways they normally wouldn't.

Or if changes in the rabbits environment have occurred like them being moved, furniture being moved around, a new pet in the house, new people in the house, loud unusual noises, strange smells, a predator hanging around outside, etc, this can sometimes set off insecurity and/or fear, which can result in sudden unusual behavior or aggression.

Another possibility when the behavior doesn't subside and you can't figure out what could be causing it, is adrenal problems. And this would need to be confirmed with testing by your vet.

https://rabbit.org/sex-hormones-in-altered-rabbits/
Spring fever usually subsides after a few weeks. Or if it could be due to a change in the rabbits environment, then it's just figuring out what that change was and correcting it if possible. But if the behavior continues or if you are concerned it's an underlying health problem causing the change in behavior, best to consult with a knowledgeable rabbit vet.

In the meantime, if this behavior is enough that a serious fight could break out, it would be best to separate your rabbits until things have settled down and/or you've been able to figure out and resolve what's causing the behavior change, as you don't want any injuries occurring.

https://rabbitwelfare.co.uk/rabbit-care-advice/behaviour/hormonal-behaviour-neutered-rabbits/
https://rabbit.org/vet-listings/