Pregnancy modulates responses to male odors in house mice

Abstract

Pregnancy induces widespread physiological and behavioral changes, yet its impact on social decision-making remains poorly understood. Here, we show that reproductive status modulates female responses to male odors in house mice, revealing striking status-specific behavioral patterns. Estrous females displayed attraction to novel male odors, consistent with a motivation to mate. In contrast, pregnant females exhibited strong aversion - an anticipatory shift likely aimed at avoiding future infanticidal males. This status-dependent approach-avoidance response was recapitulated to the male urinary pheromone darcin, highlighting its robustness as a male signal. These findings suggest that reproductive status modulates odor-driven decision-making, balancing mating opportunities with offspring protection. This shift is likely mediated by hormonal fluctuations such as rising progesterone and estrogen, that act on neural circuits involved in olfaction, threat detection, and social motivation. Behavioral responses were further shaped by the richness and context of social odors, supporting combinatorial processing of urinary pheromones. This aligns with mechanisms such as stud odor imprinting and self-referential matching for inbreeding avoidance. Overall, our results point to anticipatory behavioral adaptations during pregnancy that prepare females for the challenges of motherhood.

Keywords: Darcin; Estrus/estrous; Major urinary proteins (MUPs); Pheromones; Preference; Pregnancy; Social odor.