Pregnancy block from a female perspective

Within a limited time after mating, exposure of female rodents to the scent of an unfamiliar conspecific male results in pregnancy termination. Since its discovery in mice, pregnancy block (or the 'Bruce Effect') has been confirmed in several other murine and microtine rodent species. Adaptive explanations for this behaviour have traditionally focused on advantages to the blocking male, but the suggested benefits to females remain controversial. Consideration of potential female benefits and the implications of female advantage in pregnancy block suggest that this behaviour could evolve with little or no reference to male advantage, and may represent a potential reproductive cost to stud males.