Female recognition and assessment of males through scent.

Scents play key roles in mediating sexual behaviour in many vertebrates, both in the recognition of opposite sex conspecifics and in assessing the suitability of different individuals as potential mates. The recognition and assessment that underlies female attraction to male scents involves an important interaction between the main and accessory (vomeronasal) olfactory systems. Female mice gain information through the vomeronasal system on nasal contact with a scent source that is essential to stimulate attraction to an individual male's scent. Three highly polymorphic multigene families contribute involatile proteins and peptides to mouse scents that are detected through specific vomeronasal receptors during contact with scent. Major urinary proteins (MUPs) provide an individual genetic identity signature that underlies individual recognition and assessment of male competitive ability, kin recognition to avoid inbreeding, and genetic heterozygosity assessment. Familiar mates are recognised in the context of pregnancy block using MHC peptides, while exocrine-gland secreting peptides (ESPs) are likely to play additional roles in sexual assessment. By associating this involatile information in individual male scents, gained on initial scent contact, with the individual male's airborne volatile signature detected simultaneously through the main olfactory system, females subsequently recognise and are attracted by the individual male's airborne volatile signature alone. This allows much more rapid recognition of scents from familiar animals without requiring physical contact or processing through the vomeronasal system. Nonetheless, key information that induces attraction to a male's scent is held in involatile components detected through the vomeronasal system, allowing assessment of the genetic identity and attractiveness of each individual male.