Maternal behavior in the rabbit: endocrine factors involved in hair loosening

¹ Departments of Biological Sciences and Psychology, Purdue University, Lafayette, Indiana, and The Roscoe B. Jackson Memorial Laboratory, Bar Harbor, Maine

Evidence for the involvement of endocrine factors in the phenomenon of hair loosening is presented. A significant degree of hair loosening occurs on the day of nest building among pregnant and pseudopregnant rabbits. In the latter it occurs between the 19th and 21st day after the induction of pseudopregnancy; in the former it occurs toward the end of gestation. Progesterone administration toward the end of pregnancy significantly depressed the extent of hair loosening regardless of the occurrence of nest building. A significant degree of hair loosening could be induced in the castrated doe by treatment with a combination of estradiol, progesterone, and prolactin for 8 weeks. Hormone treatments of a shorter duration that induced nest building did not produce any hair loosening. Although nest building and hair loosening are correlated in time, the two phenomena can occur independently of each other and appear to be governed by separate mechanisms.