Rabbits are much happier when they have a friend to share their life with. They are emotionally and physically healthier because their friend offers companionship and can groom places that are difficult or impossible to reach.
Step #1: Research & Preparation
Bonding is a stressful yet rewarding endeavor. It is rare that two bunnies will meet and get along instantaneously. It is your responsibility, as their owner, to safely introduce bunnies to avoid potential injuries while the animals develop a hierarchy.
You must be able to provide separate housing accommodations until the bond has been established. This also means you'll need another litter box, water bowl, food dish, etc. to set up the second space. It can take several weeks or even months for a bond to build between rabbits. Once bonded, rabbits should be housed together in a spacious area that can accommodate them both comfortably.
Step #2: Find a Match
Boy and girl: one of the easiest, often fall in love at first sight, but not always.
Girl and girl: sometimes easy, often fighting.
Boy and boy: sometimes easy, sometimes difficult, usually fighting at first, but not impossible.
Two babies: extremely easy.
Three or more rabbits: Difficulty varies, depending on sexes, personalities, and whether or not two of the rabbits are already bonded.
Baby and adult: Sometimes difficult, but goes well if the adult is tolerant.
Size does not make a difference in whether the rabbits will bond or not, but age is a consideration. An older rabbit would be much happier with a companion closer in age rather than a young one that is full of energy and vice versa.
Step #3: Neuter / Spay
Before attempting an introduction, the rabbits should be spayed or neutered. A full two weeks after the surgery and before the introduction should be allowed to ensure proper healing and time for hormones to balance.
Beware: bucks can stay fertile for up to four weeks after the procedure and may still be hormonal during this period.
Step #4: Side-by-Side Enclosures
When the animals first see and smell each other, they may be antsy. This is normal but should dissipate within a week or so. Once they are comfortable in the presence of another bunny in side-by-side enclosures, try swapping litter boxes, blankets, and toys to transfer scents.
Step #5: Introduction
This is an extremely important step. Prepare a neutral area where neither rabbit has been housed before. Someone should sit with the bunnies in the empty pen to supervise the introductions.
Possible neutral spaces might include:
A pen in an area of the house your rabbit is not usually in
A bathroom the resident bunny has not been in
A friend's home
If love at first sight occurs, you can try them in the space they’re going to live in. If it’s still good, then they’re fine, and you have nothing else to do. If tentative friendship occurs, just watch them when they’re together, keep them separate when you’re not around, and if no fighting occurs, they’ll eventually become friends. If the (neutered) male mounts the female, and the female does not mind, then this is usually a sign that the relationship will go well. If she instead becomes aggressive towards him, then you must prepare for a lengthier introduction period. If one is chasing, and one is running, just make sure the one running doesn’t fight back and doesn’t get hurt.
If none of these things occur, then just watch and wait. If one gets hurt, then separate them and go slower and if one fights back, then you must prepare for a lengthier introduction period.
You may want to wear thick gloves and a long-sleeved shirt for initial bonding sessions in case a fight happens. A squirt of water on the nose can often prevent aggressive behavior. An initial fight can hinder future bonding success.
If the bunnies show any signs of aggression, try:
A laundry basket on top of a dryer that is on
The backseat of a moving car
The noise and movement will be slightly frightening to the bunnies and they may snuggle up and draw comfort from each other, creating positive memories of one another. They'll associate the other rabbit with a sense of security, as opposed to carrying bad memories around with them.
Work with the rabbits daily for at least 15 minutes. The more often you work with them, the quicker the process will progress (usually). If the rabbits have a bad experience, or if one of the rabbits is elderly or has health considerations, you may need to take it slower or take some time off.
Step #6: Body Language
It’s completely natural that one rabbit will be dominant over the other, but it shouldn’t be aggressive. There may be mounting, but it should be accepted by the less dominant rabbit. The subordinate rabbit shows its acceptance of the other’s dominance by licking it. The rabbit that puts its head down to be licked is claiming the top spot, and by licking it, the partner is accepting that the other rabbit is boss!
Sitting or lying side by side
Grooming each other
Seeking each other for positive interactions
Behaving normally around one another
Step #7: Unsupervised Bonding
Once your rabbits have paired up it’s super important to keep the bond alive. If one of your rabbits needs a vet, then take them both in the same carrier. Once the rabbits are spending one to two hours together daily without any problems they can be introduced into their intended living space, initially under supervision.
Rabbits can be left alone together safely once they're showing positive behaviors towards one another.
Once your rabbit has a friend, he/she will not forget you! Like humans, rabbits can have many individual relationships. You may even find that your rabbit is more friendly and outgoing once bonded with a companion.
House the rabbits separately but close together. They will get used to seeing each other and to each other's scent if they are close to one another. Make sure the cages are not close enough for them to be able to bite each other.
Be prepared for this to take several months.
Expect that there will be bumps and setbacks.
Make the effort to think like a bunny. Is one rabbit jealous you are interacting with the new bunny/resident bunny? Is he mad you just gave his favorite toy to the other? Is the rabbit stressed and ready to stop for the day?
Interact with the bunnies, but give equal attention and provide a positive and relaxed atmosphere.
Expect love at first sight.
Hold a bonding session in the resident bunny's territory until after the bunnies spend at least 30 minutes together in a neutral space. Be prepared for the potential that the resident bunny may become defensive or aggressive at first.
Try to bond if you have had a bad day. Your emotions will transfer to the bunnies and can undo weeks of work.
Leave the rabbits unsupervised, even for a minute, until they're fully bonded.
Assume that because yesterday went well, today will too.
End on a bad note, if possible.