Pseudopregnancy: hay gathering and fur plucking behavior
Esther van Praag, Ph.D.
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Once a female rabbit reaches sexual maturity, she may go through periodic false pregnancies. False pregnancies can be triggered by the mounting behavior by a castrated male or another female rabbit in an attempt to establish dominance, the presence of a castrated or intact male in the same living environment. It is, however, also observed in female rabbits that have no contact with other rabbits.
Pseudopregnancy is the result of ovulation and the release of ova. The corpus luteum and the uterus begin to develop and prepare for gestation and mammary glands may swell. Since there is no fertilization of the ova, the levels of hormones that promote gestation remain low. Around the 12th day of the pseudopregnancy, the corpus luteum and the uterus start to regress, accompanied by mammary gland involution. Between the 15th and 18th day, an increase in estrogen secretion and a drop in progesterone level occurs. These changes trigger maternal behavior and loosening of the hair. While building her nest, the female rabbit will pull out abdominal or shoulder hair and begin frenetic gathering of various materials (e.g., hay, paper) to use in its construction. This behavior lasts 1 to 3 days, after which the rabbit resumes its usual habits.
Hormonal fluctuations cause the rabbit tremendous stress and can lead to aggressiveness, growling and biting the days preceding the nest building. Pseudopregnancies can become chronic when a female remains intact, increasing the risk of developing reproductive disorders such as pyometra, hydrometra, or uterine adenocarcinoma, and/or mastitis.
Pseudopregnancy should not be confused with abnormal fur chewing activities: fur chewed and bitten off over the entire body, or this is performed on another rabbit when living as a bonded pair or in a group. Causes include stress, the presence of skin parasites, overcrowding, boredom, and seasonal factors.
Fur-collecting behavior should not be confused with the plucking and ingestion of fur observed in nursing does or rabbits that suffer from mineral nutrient or fiber deficiencies in their diet.
Rarely gathering and transport of nesting material is observed in castrated male rabbits. A nest is made, but there is no fur plucking behavior. The etiology of this behavior is not well understood; hermaphrodism or hormonal disbalance have been ruled out. It usually stops when the rabbit grows older.
Nest building and hair pulling behavior is indicative for pseudopregnancy when an intact female rabbit lives in an environment with no other rabbits, or shares space with a neutered male (neutered at least several weeks prior so that he is no longer able to impregnate) or with another female. Extensive hair-pulling is indicative of the end of a pseudopregnancy or gestation phase. Bald spots with healthy looking skin appear on the dewlap, shoulders, or ventral abdomen, and expose the nipples. Damaged or torn skin can result in secondary skin infections.
The treatment of choice for hormonally-driven fur-plucking behavior is ovariohysterectomy. This surgical procedure will, furthermore, help prevent the onset of other fatal reproductive disorders frequently observed in unaltered females, such as uterine cancer, endometrial hyperplasia, mammary gland disorders. If pseudopregnancy is accompanied by a secondary disorder or infection of the genital tract, it is important to stabilize the health of the rabbit prior to surgery with appropriate drugs and supportive treatment.
For detailed information on pseudopregnancy in rabbits:
by Esther van Praag, Amir Maurer and Tal Saarony,
2010, 408 pages. $85.-
My gratitude goes to Arie van Praag (Switzerland) and Kim Chilson (USA) and her rabbit Carson for their pictures.
Meredith A, Flecknell P. BSAVA Manual of Rabbit Medicine and Surgery Second Edition BSAVA, 1 Telford Way, Quedgeley, Gloucester, GL2 2AB, UK. 2006
Quesenberry KE, Carpenter JW. Ferrets, Rabbits and Rodents - Clinical Medicine and Surgery. Second Edition. WB Saunders, Philadelphia, Pennsylvania, USA. 2004.