The researchers have named the pheromone 'darcin,' after Jane Austen's hero in Pride and Prejudice, Mr Darcy. Darcin stimulates females to 'learn' an individual male's scent, reinforcing their memory of sexual attraction to that same male.
Previous studies have shown that many mammals, from mice to elephants, use urine to communicate sexual attractiveness. In mice, females learn attraction to a male's scent through contact with urine and recall their attraction when the scent is detected at a distance.
The Liverpool team looked for the chemicals that conveyed this attractiveness. They investigated major urinary proteins (MUPs) in mouse urine, which act like a chemical 'barcode' of individual identity and kin recognition. For the first time, the team has now demonstrated that one of these MUPs - darcin - is essential for female attraction to male mice.
Darcin has the ability to stimulate the female's brain to remember the attraction towards a particular male, and favour this mouse above all others. Although darcin is not present in humans, it is possible that there are other chemicals that perform similar functions.
Professor Jane Hurst, who leads the University's Mammalian Behaviour and Evolution Group, explains: 'We knew that MUPs acted like a 'barcode,' allowing female house mice to identify mates that could give them better offspring, but we also suspected that individual MUPs had special roles. We have now shown that darcin is a protein pheromone that coordinates sexual recognition and attraction.
'We observed the behaviour of more than 450 female mice as they reacted to two urine scent marks, one male and one female. Darcin doubled the time a female spent near a male scent mark. Touching darcin in urine marks with their noses stimulated learning of the male's odour, which tripled the time they subsequently spent near the airborne scent of the same male.
'Our work emphasises the importance of studying the behaviour of wild mice. Understanding the subtleties of these chemical signals in mice might help in the development of new methods of pest control. The economic impact of rodent-mediated damage, to food, to buildings and in the transmission of disease runs to many billions of pounds worldwide.'
The research, in collaboration with the University's Proteomics Group, led by Professor Rob Beynon, is published in BMC Biology.