Unravelling information flow and olfactory eavesdropper networks in murine rodent communities

Functional roles of mammalian pheromones have routinely been investigated in an intraspecific context, such as territorial marking and sexual signaling. Sex pheromones, being innately conspicuous against a 'noisy' background to enhance detection by the intended receiver, are especially susceptible to interception, or eavesdropping, by heterospecific community members. Only recently was it discovered that predators are attracted to heterospecific predator scent, demonstrating intra-guild eavesdropping, but the underlying semiochemicals (message bearing chemicals) remained unknown. Here, I investigated the olfactory interceptive eavesdropper network and information flow in a murine rodent community. First, I identified new pheromone components of female and male house mice, Mus musculus, as well as male deer mice, Peromyscus maniculatus. Headspace volatiles emanating from urine and feces excreta of males or females were collected and analysed by comparative gas chromatography-mass spectrometry (GC-MS). Candidate pheromone components were synthesized or purchased and tested for their attractiveness to rodents in both laboratory and field experiments. I discovered three new sex attractant pheromone components produced by female house mice (butyric acid, 2-methyl butyric acid and 4-heptanone) that attract conspecific males, two new pheromone components produced by male house mice (1-hexanol and 2,3,5-trithiahexane) that synergistically attract conspecific females, and a blend of nine ketones produced by male deer mice (3-methyl-2-pentanone, 5-methyl-2-hexanone 4-heptanone, 2-heptanone, 6-methyl-2-heptanone, 3-octanone, 2-octanone, 2-nonanone) that, together with testosterone, attracts conspecific females. With these pheromone components in hand, I then investigated their exploitation by murine community members to elucidate the flow of olfactory information between species, guilds, and trophic levels. First, I tested for, and in field experiments experimentally demonstrate, intra-guild eavesdropping by wild brown rats, Rattus norvegicus (predator of mice), and wild house mice (prey of brown rats). Next, I tested for, and in animal shelter and field experiments demonstrate, inter-guild predatory eavesdropping by domestic and feral cats, Felis catus (predator of mice), on rodent-derived pheromones and sound signals or cues. Finally, I investigated olfactory information flow between two distantly related phyla, rodents and bumble bees, Bombus spp.. I show that queen bumble bees sense, and behaviorally respond to, (synthetic) rodent odor when they seek abandoned rodent burrows as nesting sites.