Mice seem to be addicted to the scent of urine and repeatedly go back to spots where they found the excretions. Researchers have discovered that this behavior is triggered by a single protein in the urine of male mice.
The scientists published their findings in the journal Science. Mice use their scent to mark their territory, advertise their dominance and convey information about their health and reproductive status. These volatile pheromones usually disperse quickly, and it was unclear what exactly stimulated females to be attracted by specific males.
Previously, research has shown that in the lab, female mice often return to a place where they had come across cage bedding soiled by males. Researchers at the University of Liverpool, in the UK, have confirmed this. Female mice spent five times as much time in a place where they encountered a dish with male urine than one where they encountered water. After 10 minutes of exposure, the urine was enough for the mice to show this place preference even after as long as 14 days.
If the mice were prevented from touching the urine with their nose, the place seemed to lose its attractiveness. The researchers then separated the urine into different fractions to discover that a protein called darcin, which mice can only detect if their nose touches urine, is responsible for the frequent visits.
The researchers found that darcin produced in the lab elicited the same reaction from mice and that the pheromones induced learning in mice. The mice learn to be attracted to the place where they encountered the darcin and they learn the odor cues of that specific male and are then attracted to it.
Reference: “Pheromonal Induction of Spatial Learning in Mice” by Sarah A. Roberts, Amanda J. Davidson, Lynn McLean, Robert J. Beynon and Jane L. Hurst, 14 December 2012, Science.