Acceleration and delay of sexual maturation in female house mice (Mus domesticus) by urinary chemosignals: mixing urine sources in unequal proportions.

Urine from male mice, from estrous female mice, and from pregnant or lactating female mice accelerate first vaginal estrus in females, whereas urine from grouped female mice delays first estrus. Nine experiments were used to test the effects of treatment of young female mice with urinary chemosignals that influence the onset of first estrus using unequal proportions of urine from the different sources. At ratios of 10-20 parts acceleratory chemosignal to 1 part delay chemosignal the acceleratory effect overrides the delay chemosignal, and the mice attain first estrus at earlier ages than controls. Ratios of about 4 to 1 up to 7 to 1 result in mean ages for puberty that are not accelerated or delayed relative to controls. Over a modest range of actual dose amounts of urine, the ratio effects are the same regardless of the actual quantities of urine employed in treating test females.