Odors in traps: Does most recent occupant influence capture rates for house mice?

Responses of house mice (Mus domesticus) to odors in live traps were studied in a series of eight 0.1-ha outdoor field enclosures. It was assumed that the most recent mouse capture would provide the predominant odor in a trap for at least one week. Three different populations were tested, one in 1989 and two in 1992, involving over 800 different mice. Similar response patterns were recorded from all three groups. Two types of questions were tested: (1) Were there any biases contingent upon what had been previously caught? (2) Were there consistent responses of mice of particular age, sex, or reproductive classes to trap odors? Traps soiled by juvenile females caught adult females significantly less often than expected, but there were no consistent relationships in terms of the effects of specific residual odors on the subsequent capture at a particular trap. For various age, sex, and reproductive classes, (1) adult males preferred odors from juvenile and estrous females and avoided odors of other males significantly more than expected, (2) juvenile females selected traps with odors of other juvenile females and avoided all other types of female odors significantly more than expected, (3) nonestrous females exhibited a significant preference for adult male odor, and (4) estrous females selected traps containing odors from adult males but avoided those that had previously contained either nonestrous or pregnant/lactating females significantly more than expected. These findings have potential implications with regard to both the methods used for trapping small rodents and the social biology of house mice.     

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.