Inbreeding and copulatory behavior in house mice: a further consideration

Comparisons were made of the copulatory behavior of randomly bred (one population: WRL) and inbred wild (five strains: PAA, ab, ac, ad, and PAE) male house mice. All inbred and randomly bred stocks were derived from a single foundation population. The inbred males tended to have shorter latencies to the first mount and intromission, longer latencies to ejaculation, and more preejaculatory mounts and thrusts than randomly bred males. All these effects parallel those observed in a previous study in which a wild population was compared with various domestic inbred strains. If inbreeding depression is related to adaptive significance, these data suggest that, although rapid initiation of copulation in a novel environment may not be adaptive, it may be adaptive for mice to ejaculate rapidly once copulation is initiated.