Fur loss

Fur loss or hair loss, also known as alopecia, in rabbits can be caused by both natural reasons as well as disorders.

Molting
Molting is a natural process that occurs 2-3 times a year where a rabbit sheds his entire old coat to expose the new. Changes in environment temperature from hot and cold weather are usually onsets of molting. Bald spots are common at this time. It is also common for a "tide mark" to develop with obvious delineations of old and new fur as the rabbit molts.

Owners should regularly groom their rabbits to minimize the amount of hair that the buns can ingest to prevent hairballs and GI stasis from occurring. Make sure that your rabbit is consuming appropriate amounts of hay and other roughage as well as water to keep its digestive tract free of fur.

The links below provide more information about molting.
 * San Diego House Rabbit Society, When the Fur Flies
 * MediRabbit, Esther van Praag, Ph.D., Varying shedding patterns among rabbits
 * Rabbit Welfare Fund, Moulting