Puberty delay by a urinary cue from female house mice in feral populations

Urine produced by wild female house mice, living in high- and low-density populations and confined to areas within a highway cloverleaf, was tested for its ability to delay puberty in juvenile female mice. Only urine collected from females in the dense population at its maximum density delayed puberty in test females. Urine collected when the population was less dense, or from a population that remained sparse, failed to delay puberty. These results suggest that a urinary factor present at high densities may delay puberty and thus help to slow further population growth.