Rates of urine excretion by house mouse (Mus domesticus): Differences by age, sex, social status, and reproductive condition.

A series of five experiments was used to test hypotheses about factors affecting excreted urine output per day in male and female house mice (Mus domesticus). Urine was collected in metabolism cages over a 24-hr period. Male house mice excrete urine at a rate 1.5-2.0 times that of females. Daily average urine output increases with age for both sexes and for mice of the same age; urine output per day is correlated with body mass. Females in estrus produce more urine than females in diestrus. Urine output per day increases during the latter two thirds of pregnancy and remains high throughout lactation. Density does not influence urine output per day for either sex over the range of densities tested. Castration reduces urine output per day in male mice, but ovariectomy in females does not alter rates of urine production. Dominant males produce more urine than subordinate males, but there are no similar effects for female mice. The findings have potential implications for our understanding of the functional and ecological uses of urine by house mice.