Urinary marking in male house mice: responses to novel environmental and social stimuli

The frequency of urinary marking by male house mice was investigated in two-chambered cages during exposure to either novel or familiar social or other environmental cues. In four experiments isolated males marked at high rates during their first exposure to the test cage (300–400 marks/hr), but showed significant habituation during subsequent testing (100–200 marks/hr on the fourth daily test). Marking frequency increased significantly when test-habituated males were placed in the presence of (in order of decreasing effectiveness): estrous females, ovariectomized females, castrate males, intact males, deermouse males, or male mouse urine. When all experiments were considered, however, there was little evidence that the various stimulus animals differentially affected marking rates. Male house mice also readily habituated to the presence of another male. Such male-habituated males then displayed a significant, but not dramatic, elevation of marking in the presence of an estrous female or a male deermouse, but they were totally unresponsive to the presence of a strange, test-habituated male. The results establish the importance of physical and/or biological novelty in eliciting urinary marking in male Mus.