Identification and Field Testing of Volatile Components in the Sex Attractant Pheromone Blend of Female House Mice Elana Varner 1 & Regine Gries 1 & Stephen Takács 1 & Stephanie Fan 1 & Gerhard Gries 1 Received: 15 May 2018 /Revised: 20 October 2018 /Accepted: 29 October 2018 # Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract Recently, it was reported (i) that the sex pheromone blend of male house mice, Mus musculus, comprises not only volatile components (3,4-dehydro-exo-brevicomin; 2-sec-butyl-4,5-dihydrothiazole) but also a component of low volatility (the sex steroid testosterone), and (ii) that the sex steroids progesterone and estradiol are sex pheromone components of female house mice. Here we tested the hypothesis that the sex attractant pheromone blend of female mice, analogous to that of male mice, also comprises volatile pheromone components. Analyzing by GC-MS the head space volatiles of bedding soiled with urine and feces of laboratory-kept females and males revealed three candidate pheromone components (CPCs) that were adult female-specific: butyric acid, 2-methyl butyric acid and 4-heptanone. In a two-choice laboratory experiment, adult males spent significantly more time in the treatment chamber baited with both the synthetic steroids (progesterone, estradiol) and the synthetic CPCs than in the paired control chamber baited only with the synthetic steroids. In field experiments, trap boxes baited with both the CPCs and the steroids captured 6.7- times more adult males and 4.7-times more juvenile males than trap boxes baited with the steroids alone. Conversely, trap boxes baited with both the CPCs and the steroids captured 4.3-times more adult males and 2.7-fold fewer adult females than trap boxes baited with the CPCs alone. In combination, these data support the conclusion that butyric acid, 2-methyl butyric acid and 4- heptanone are part of the sex attractant pheromone of female house mice. With progesterone and estradiol being pheromone components of both female brown rats, Rattus norvegicus, and female house mice, these three volatile components could impart specificity to the sexual communication system of house mice, brown rats and possibly other rodent species. Keywords Female house mice . Mus musculus . Sex pheromone . Sex attractant . Volatiles Introduction Communication of murine rodents is remarkably complex, involving multiple modalities of information conveyance, in- cluding olfaction (Arakawa et al. 2008; Hurst 1989), contact chemoreception (e.g., Breer et al. 2006; Fuss et al. 2005; Kimoto et al. 2005; Luo et al. 2003; Moncho-Bogani et al. 2002) and sound (e.g., Holy and Guo 2005). Each signalling pathway comprises a plethora of intricate and nuanced signals. Vocalizations of house mouse, Mus musculus, e.g., vary de- pending upon both the age and sex of the signaller (Clancy et al. 1984; Osada et al. 2008; Stowers et al. 2002; Wysocki and Lepri 1991) and the context of signalling (Grimsley et al. 2011). Ultrasonic courtship songs of male mice rival the complexity of courtship songs in birds (Heckman et al. 2016; Holy and Guo 2005). Olfaction and contact chemoreception of mice and rats are equally sophisticated. Two types of receptors, the main olfac- tory epithelium and the vomeronasal organ, sense pheromone components of diverse chemical classes and functions (Chamero et al. 2007, 2011; Fu et al. 2015; Haga et al. 2010; Haga-Yamanaka et al., 2014; Kimoto et al. 2005; Leinders-Zufall et al. 2000; Takács et al. 2017) at sub- nanomolar levels (Spehr et al. 2006). Pheromones in urine deposits of mice and rats offer a wealth of information about the signaller, including its age (Osada et al. 2008), health (Kavaliers et al. 2005), breeding status (Hurst 1989; Mossman and Drickamer 1996), domi- nance (Jones and Nowell 1973), kinship and individual iden- tity (Barnard and Fitzsimons 1988; He et al. 2008). Urine deposits even have a timestamp informing the receiver of how recently they were placed (Hurst and Beynon 2004). Mate location, attraction and assessment in house mice take place at night and thus are reliant primarily on chemical and * Gerhard Gries gries@sfu.ca 1 Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada Journal of Chemical Ecology https://doi.org/10.1007/s10886-018-1032-3