Chemosignal effects on puberty in young female mice: urine from pregnant and lactating females.

A series of 8 experiments tested the effects of urine from pregnant and lactating female mice on sexual maturation of young females. Urine collected from females at various intervals during pregnancy and lactation and painted on the nares of young test females produced different effects on the age of puberty depending upon the collection interval. The urinary substance which accelerates puberty is found in the bladder urine of both pregnant and the lactating females as well as in the excreted urine of females that are both lactating and also simultaneously pregnant. Four separate experiments demonstrated that grouping pregnant or lactating females at various densities, either with other females in the same stage of reproduction, or with nonreproductive females, resulted in excretion of urine which did not accelerate or delay puberty in young test mice. These results conform with a general hypothesis regarding the release of urinary chemosignals in female house mice as indicators of the adequacy of social and environmental conditions for successful reproduction.