Hair pulling is the most common reason apart from illness for loss of hair in rabbits, but this is mainly during pregnancy and so not the case this time. Illnesses that can cause hair loss include Ringworm infections (also causes scaly skin); Mites; Trauma to the skin caused by wire floors and hard surfaces; Skin infections.

Because of the seriousness of some of these conditions, I strongly advise you to visit your vet, where at the very least he can rule out any medical condition. Make sure you are providing as comfortable a home as possible for your rabbit to rule out the chance that this is caused by the rubbing of wire mesh or a dirty floor.