Pheromones and novel male-induced pregnancy disruptions in mice: exposure to conspecifics is necessary for urine alone to induce an effect

Previous research indicates a role of pheromones in novel male-induced early pregnancy disruptions. Although some reports suggest that urine alone is sufficient to produce this effect, others raise procedural concerns and fail to replicate such effects. On Days 1 to 5 after insemination, female CF-1 mice had their nasal regions repeatedly painted with water, urine from males housed in isolation, or urine from males housed in proximity to females. Almost all (87.5%) of the control females delivered litters. There was a small nonsignificant reduction in proportion parturient (78.5%) among females exposed to urine of males housed without social contact. The proportion of females parturient (57.1%) after treatment with urine from males housed in proximity to females was significantly different from controls. The magnitude of the effect of socially stimulated male urine is substantially less than that recorded when males are housed directly above inseminated females separated by a wire-mesh grid. These data suggest that production of pregnancy-disrupting male pheromones is stimulated by contact with conspecifics.