Once in a while, a rabbit will give birth somewhere other than a nest box. The husbandry terminology for this is "a doe kindling on a wire." When it doesn't have the tight confines of a nest box, a baby bunny or kit can get separated from its littermates or the mother doe. This is dangerous for newborn bunnies since they are born blind, deaf, and hairless with less than paper-thin skin. They become chilled quickly and exposure can kill them in minutes.
There are several ways that you can try to safely warm up a baby bunny to the point it can be returned to the warmth of the nest box, its siblings, and mother. Unlike cats or dogs, rabbits do not retrieve or transport their young. Without human intervention, there is no way the furless baby bunny can get back into the nest box. It will surely die if left alone.
Assess the Bunny
Do not panic (even if it is not moving). Take a good look at the bunny. If the kit is warm and moving about, he may have just recently wandered and simply needs to be placed back into the nest box with his siblings where he will warm up quickly.
If the bunny is cool or cold to the touch, do not immediately assume that it is dead. Kits will become very still when their temperature drops to preserve energy, which keeps them alive as long as possible.
Use Body Warmth
There are a few things that you can do to warm up baby bunnies. The first thing you can do, which requires no preparation, is to place the kit under your shirt up against your warm skin. The baby should begin to warm up immediately. You may even feel its feet starting to move.
Try a Heating Pad
You can use a heating pad to warm up the little one. Wrap the pad up in a towel and place it on the lowest setting. Put the heating pad and towel and the bunny inside a shoe box so the heat surrounds it. It is best to warm the bunny up slowly. Do not give in to the urge to turn the pad up to a high setting. A newborn's skin can burn easily. Do not leave the bunny alone with the heating pad. Feel the pad regularly to be certain the pad is not getting too hot. After the baby is warmed up and wriggling, place it back into the nest box with his littermates.
Give It a Waterless Warm Water Bath
Another technique is to put warm water into a bowl on the counter. Place the kit into a storage baggie (be sure to leave the top open and hold it securely) and place the storage baggie in the water bath so that the baby is laying against the warm water inside the baggie. The idea is not to let the water touch the kit, but to let the warm water heat its skin through the plastic bag.
Use Warm Towels
You could also put hand towels into the dryer and once they warm up (not hot) simply hold the kit in your hands with the towel wrapped around it. Once the hand towel cools, wrap the baby bunny in another warm towel from the dryer. Do this until the bunny pinks up and is quite warm without the towels.
Return the Kit to the Nest Box
Before returning the kit to the box with the rest of the litter, it really needs to be fully (and slowly) warmed up without any chill to its little body. If it's still cool, the other kits will wriggle away from it. Without their body warmth, the newly warmed bunny could become chilled again and die.
When a Kit Fails to Recover
Sometimes a baby can be brought back from the brink of death, only to gape, gasp, and die even though it seemed you were able to warm it up. You have to realize that you did what you could, but some kits are just too far gone to be brought back. This is the unfortunate and not-so-fun part of rabbit raising.
Check on Pregnant Bunnies and New Litters
This fear of does kindling on a wire is one very important reason to check frequently on rabbits that are pregnant and due to give birth.
In another sad scenario, a newborn may be safely in the nest box, nursing, but then the doe hops out of the box with the baby unwittingly still attached to the teet. The baby falls off, gets separated from the nest, and cold exposure begins. Check frequently on new litters to make sure kits don't get found on the wire.