Spay/Neuter

Before getting to the problem, the background info:

Male, Dax, ~4-5 years old, neutered years ago, Mini Rex, black

Female, Venti, ~1 year old (shelter says 6mo, but she’s too big for that), spayed about 25 days ago, New Zealand, white

Prior to this, Dax has been the only animal in the house since adoption 3 years ago, and the only animal at this apartment for the one year we’ve lived here. Venti was rescued as a stray about a month ago. Our bonding process was setting her up in one bedroom (where Dax went, but infrequently, and we put her in a portion of the room he never goes to), and allowing Dax to meet her, which initiated some humping from Dax that we probably broke up a little too quickly. Following this, we’ve tried a couple sessions of table bonding which didn’t seem to work well, and adjacent housing with  set of modular 3′ fence panels. After that, we tried putting them together in a carrier, driving around, then placing them together  in a gradually-expanding space, up to a maximum of a pentagon 3′ on each side.

This went generally pretty well. It’s only been about 6 days and they don’t really fight anymore, despite having spent the last 3 and a half days together 24 hours a day. There is, however, a lot of nipping from Venti, so much so that the first night we had to put her in “jail” (sat in the pet carrier for a while, while Dax roamed) so Dax could calm down.  The fights have gotten better, but the nipping continues, and it’s stressing Dax out enough that I think it’s preventing him from grooming her. I’ve tried the trick of putting food on their heads, and Venti has taken to it well, grooming Dax for minutes at a time, but Dax seems too afraid to touch her (usually resulting in a nip I can only interpret as “Hey, I cleaned you. Return the favor!). Only this morning did I get Dax to groom her for a couple minutes, but the nipping continues from Venti any time either one approaches the other. Dax has only bitten us twice in his life, once when I held him too long while transporting him somewhere, and once during this bonding process, so I don’t think he understands the way Venti is using it as her standard method of communication.

I understand light nipping is one way rabbits establish dominance and communicate “get out of my way,” but it seems to be hurting Dax’s ability to bond, causing him to run away any time she approaches “his” side of the enclosure. Is there a way to discourage the nipping effectively? I think part of the problem is that Dax doesn’t seem to really “understand” territory, having been free-roam for so long. His cage where his water bowl is located is “his” in the sense that when he goes there it communicates to us he doesn’t want to be interacted with, but beyond that he seems to understand the house is a shared space wrt humans at least. Venti, likely due to being a stray until recently, is much more territorial. They can share a litter/hay box with only eventually getting fed up with the other’s presence, though Venti will eventually establish it as her territory given enough time with it in the enclosure. I think they’re improving steadily, but I feel like something has to be done to curtail this nipping if I don’t want to be bonding them for months.