Are they both spayed/neutered?
In fixed and bonded bunnies this behavior seems territorial like you suggested. Have there been any changes to their environment where they might feel inclined to act differently? New smells could also trigger this kind of behavior.

Hmm, with things like this I always think about what would happen if you weren’t there to break it up. Have you ever waited to see if they stop it themselves? That would be my concern. My Peanut used too (not so much now *touch wood*) get very interested in Buttercup’s bum and would try and sniff and then she’d try and sniff his bum and they’d essentially be circling but I never had to intervene because they stopped it themselves. There was no humping though.

If they are both fixed, this means their bond isnt cemented or something disrupted their bond. If they are not both fixed, they are likely to get worse with this until you get them both fixed.

I also suspect that the stress of moving to a new home, along with the new smells encountered, may have caused a few – temporary, I hope!!! – issues with Panda and Fernando’s relationship, as the OP and @LongEaredLions suggest. Panda engaged in a bit of dominance behavior with Fernando Monday evening, mounting him a couple of times, which Fernando accepted placidly, and I was watching VERY closely like Aaron to make sure they didn’t get into a quarrel. Happily, though, they stopped after a minute or so of this, didn’t go into circling one another, returned to normal behavior and seem to have cuddled and made up; they were snuggling to each other in totally adorable fashion last night – Panda was kind of “bunny-rugged” while Fernando was grooming his mom. I think they’re still marking their territory, particularly Panda.

What happens if you don’t intervene?

Posted By Aaron on 8/23/2017 12:40 PM

They are both fixed, we did just return from a vacation and the rabbits came with us. 1 hour drive, and they got back home with us to their cage. The humping skit happening yesterday and we returned on Monday. They do sometimes get into these skits, but right after, they lay together, eat together, grooms each other, etc.

I’d guess the experience of travel, which can be very stressful for rabbits, is also playing a role. They’re probably still readjusting to being back home, and if they’re behaving normally with each other most of the time, I think (fingers crossed) the humping will end in due course. As I said, my own buns have just been through a HUGE life-change, with a car ride thrown into the mix to boot, so I’m not surprised, now that I think about it, that they’re engaging in occasional behavior not unlike yours.

Posted By Aaron on 8/24/2017 12:45 PM

If I do not intervene, they stop the whole thing. He may chase her for a few seconds but after that, they love each other again. I suspect that she is a bit territorial.

Or it could just be as simple as that she’s reasserting her status as the dominant member of the pair. I found a thread from two years ago discussing whether spayed bunnies still have sexual tendencies:

https://binkybunny.com/FORUM/tab…fault.aspx

and the last post, by @LBJ10, stated that “dominance humping” is definitely a thing engaged in by altered rabbits. Also, @Q8Bunny pointed out to me earlier this morning that in the wild, bunnies living in warrens – remember that all domestic rabbits are descended from the European rabbit, which lives in large warren/burrow communities – live in a matriarchal social order.

I’ve seen Panda, on the occasions this week when she’s been doing this behavior, mount Fernando – who always peacefully submits – from both front and rear in quick succession. During these occasions, she also exhibits a rather curious behavior wherein she shakes her head quickly at regular intervals, every 15-30 seconds or so, for a couple of minutes, and then returns to normal. I wonder if this is another demonstration of dominance, or perhaps annoyance? Does your own female bunny show this same behavior when humping/mounting her bondmate?

My current speculation is that this is going on partially because of the stress caused by the change from their previous living environment with their foster mother (where they were surrounded by seven other bunnies, in fact) to a whole new world where it’s just themselves and me. There’s also the fact that a new “partner” – myself – is being factored into the relationship, working to bond with both of them; Fernando is adapting quicker and more easily than Panda, getting to the point last evening where he accepted a long pet-and-caress session with every sign of pleasure. Panda, the more standoffish of the pair, only allowed me to touch her for longer than a couple of seconds for the first time last night, which is actually quite good progress, I think. I have the gut feeling now, having learned more about this, that Panda is trying to reassure herself that she’s still “top bunny” in the pair, and so is your own bun.

EDIT: Stop the presses! I found another old BinkyBunny thread (from 2009!) on this very subject.

https://binkybunny.com/FORUM/tab…fault.aspx

It seems that this is, in fact, entirely normal behavior for a bonded pair. Your bun – and Panda – are just demonstrating who the boss is, and if they’re not doing anything more aggressive than mounting/humping, there’s nothing to worry about. I guess I was wrong about the move being a possible cause; it may well be that there’s a bit of stress still going on, but the kind of behavior we’re both seeing may well be totally unconnected.

Posted By Aaron on 8/24/2017 12:45 PM

If I do not intervene, they stop the whole thing. He may chase her for a few seconds but after that, they love each other again. I suspect that she is a bit territorial.

I’m not sure what to make of it all but I think it’s a very good sign that it doesn’t escalate without intervention. Hopefully someone more experienced will chime in but I do think it’s great that no bun tries to take it any further. 

Posted By sarahthegemini on 8/24/2017 1:37 PM

Posted By Aaron on 8/24/2017 12:45 PM

If I do not intervene, they stop the whole thing. He may chase her for a few seconds but after that, they love each other again. I suspect that she is a bit territorial.

I’m not sure what to make of it all but I think it’s a very good sign that it doesn’t escalate without intervention. Hopefully someone more experienced will chime in but I do think it’s great that no bun tries to take it any further. 

If I’m right about what I think is going on, then (fingers crossed) that’s all it amounts to, just asserting/reasserting dominance in a bonded pair. I still wonder why Panda shakes her head like that during those incidents, though. She only ever does that then, so it’s got to be some kind of rabbit body language. (UPDATE: Did some more research digging, and ten gets you one that’s exactly what it is; in this case, she’s showing that she’s excited.)

EDIT 7:20 PM: Just came back from the bathroom to find Panda and Fernando at their little dominance-submission ritual again. This appears to be becoming a regular thing, if it wasn’t before they moved in with me, and they always seem to do it at about the same time of day. I know bunnies are great creatures of habit, but this may be overdoing it a bit.