Identification and field testing of sex-attractant semiochemicals produced by male deer mice, <i>Peromyscus maniculatus</i>

Following previous reports that male deer mice, <i>Peromyscus maniculatus</i>, produce chemical signals that attract conspecific females, we analysed and field-tested sex-attractant semiochemicals (message-bearing chemicals) of male deer mice. Field traps baited with urine- and faeces-soiled bedding of male mice captured adult female, but not male, mice, indicating dissemination of sex-attractant semiochemicals from the males' excreta. Analysing excreta headspace volatiles of both males and females by gas chromatography-mass spectrometry revealed that 5-methyl-2-hexanone was male-specific, and that eight other ketones (3-methyl-2-pentanone, 2-hexanone, 4-heptanone, 2-heptanone, 6-methyl-2-heptanone, 3-octanone, 2-octanone, 2-nonanone) were 2.6-5.6 times more abundant in male, than in female, samples. In a field experiment with paired trap boxes, treatment boxes baited with the synthetic ketone lure captured 3.4 times more females (17 : 5) and 1.6 times fewer males (5 : 8) than corresponding unbaited boxes. In a follow-up paired-trap field experiment, treatment boxes baited with both the ketone lure and synthetic testosterone captured 8 times more mature females and 2.3 times more immature females, but 9 times fewer immature males, than control boxes baited only with the ketone lure, all indicating that testosterone is a synergistic sex-attractant semiochemical. As previously shown in house mice, <i>Mus musculus</i>, and brown rats, <i>Rattus norvegicus</i>, sex-attractant semiochemicals of male deer mice comprise both volatile and sex steroid components.