Pregnancy Modulates Responses to Male Odors in House Mice

Abstract

Pregnancy drives profound physiological and behavioral changes in females, yet its impact on social decision-making remains poorly understood. In this study, we investigate how reproductive status modulates female responses to male odors in house mice, revealing striking reproductive status-specific behavioral patterns. Estrus females strongly preferred novel male odors, reflecting an interest in mating, whereas pregnant females exhibited robust aversion, likely to reduce the risk of encountering infanticidal males. This approach-avoidance response was recapitulated to the male major urinary protein pheromone darcin, highlighting its robustness as a male signal. Our findings suggest that reproductive status modulates odor-driven decision-making, balancing mating opportunities with offspring protection, likely through hormonal fluctuations that shape underlying neural circuits. However, preference behaviors appear to further be influenced by the richness and context of social odors. Our results support the combinatorial coding of urinary pheromones, consistent with research on stud odor imprinting and self-referential matching for inbreeding avoidance. Additionally, they highlight the critical role of both the presence and absence of information in interpreting social signals.

Note:
Funding declaration: This research was funded by USDA Hatch Grant (NYC-191428; Michael Sheehan).

Conflict of Interests: The authors declare no competing interests.

Ethical Approval: All experimental protocols conducted at Cornell University were approved by the Institutional Animal Care and Use Committee (IACUC: Protocol #2015-0060) and followed the NIH Guide for Care and Use of Animals.

Keywords: pregnancy, estrus, social odor, pheromones, darcin, major urinary proteins (MUPs), preference