Can you share how old they are, whether they are spayed, and if they were labelled as “bonded” rabbits when you learned about them?

My instinct is they are not playing, but they are establishing dominance with one another, which can become dangerous, especially since you express that the frequency and intensity is increasing.

Rabbits hormones change them much more than human hormones change us. Rabbits can be together since birth, be sisters or brothers, but as the grow and their hormones develop, this “baby bond” disappears and it can reduce down to two rabbits going against each other to work out territorial disputes and expressing mating frustration.

This may sound odd since you’ve had them together since the beginning, but since hormonal behaviors are appearing and ramping up, it may be safest to separate them and go through the formal *bonding process*. You can find information on how this can be done on the BUNNY INFO section of this website.

New surroundings can be a trigger, but an overnight change in relationship is common for the hormonal behavior I talked about.

I would recommend separating them and following the steps outlined in the bonding information.

You need to neuter both, wait a month or two (pre bond during this time) and then start physical introductions.

Just a note – a cage should not be a ‘punishment’ Both buns need to be in ample size enclosures that allow them to run and binky. Your aggressive rabbit doesn’t need ‘punishing’ either. He is acting like a hormonal rabbit. Perfectly normal. I know it seems like the aggressive one is being nasty but bunnies aren’t mean for the sake of it. Hormones make them territorial so what you’re seeing whilst unpleasant, is totally normal

https://binkybunny.com/BUNNYINFO/tabid/53/CategoryID/9/PID/940/Default.aspx

… Will give you an outline.

Posted By Bunny & Fluff on 10/10/2018 7:59 AM
Oh no it’s not a punishment, it’s a smaller enclosure but it is big enough. I let her come out and run around anyway but I meant that the cage is smaller so it’s technically a punishment haha. What will happen if I don’t neuter them? Will this behaviour subside if I wait long enough?

No, rabbits with hormones intact are unpredictable which is why it’s unsafe to try and bond when they’re not neutered.

Exactly what Sarahthegemini said above – but also, you said they were both females. 70% (or higher) of un-spayed female rabbits will develop uterine cancer by the age of 4, and the odds get higher every year that passes. If they are spayed this 100% eliminates that risk and they can live to a nice old age of around 10!

So to double their life expectancy it is also worth it for that reason too! (as well as being able to have them back together for companionship)

Sorry, you were replying while I was typing my reply.
I know it is more expensive for a Spay, but as I said, it will eliminate the risk of uterine cancer.

I still had both of mine done, not just the one, as the hormones of the one that isn’t fixed can still cause the other to react.

Having them fixed is the only real way to have them together with a stable relationship and will eliminate almost all aggression for territory and hormonal reasons.

We can’t guarantee that they will 100% successful bond together after they both have the surgery… but I would say 90% as almost all bunnies can be bonded. It’s more rare that they can’t.

BUT they also 100% wouldn’t bond with out the spay if they wouldn’t bond with it.
(does that make sense)

As for the fear of the operation – you need to find a Rabbit savy vet in your area. Ask them what their success rate is. 
The one I found had done over 500 spay/neuters on rabbits and had only lost one male in that entire time. They found out after the rabbit had a heart issue that was not detectable before the surgery. 

Yeah as Nutmeg said, they BOTH need spaying.

Almost all aggression that you see rabbits exhibit is due to fear or is territorial. Take away the hormones and the territorial behaviour will subside a little. Pre bonding for a sufficient amount of time will also get the aggression to subside.

Even if you decided not to bond them, they both need spaying anyway for their health. I understand that it’s expensive but it is absolutely essential that you spay them.