Urinary chemosignals, reproduction, and population size for house mice (Mus domesticus) living in field enclosures.

The effects of urinary chemosignals influencing reproduction and puberty were studied in free-living house mice maintained in six 0.1-ha outdoor enclosures. Two enclosures were provided with urine and soiled bedding from male mice, two with urine and soiled bedding from group-caged female mice, and two with water and clean bedding as a control. Reproduction, puberty, recruitment, and population size all were affected by the urine treatments. Overall, populations reached significantly greater numbers in the enclosures treated with male urine and soiled bedding, intermediate levels with the water and clean bedding treatment, and were lowest for enclosures treated with urine and soiled bedding from grouped females. The population differences resulted from urinary chemosignal effects on adult female reproduction and female puberty; in general, females were in higher states of reproductive condition, more pregnancies occurred, and young females attained puberty earlier in male-treated enclosures and later in female-treated enclosures than in control enclosures. Urinary chemosignals that affect endocrine physiology and related reproductive processes may be one mechanism by which various factors influence population size in house mice.