An appeasing pheromone ameliorates fear responses in the brown rat ( Rattus norvegicus ).

The brown rat () is one of the major animals both in the laboratory and in urban centers. Brown rats communicate various types of information using pheromones, the chemicals that mediate intra-species communication in minute amounts. Therefore, analyses of pheromones would further our understanding of the mode of life of rats. We show that a minute amount of 2-methylbutyric acid (2-MB) released from the neck region can ameliorate fear responses both in laboratory rats and in wild brown rats. Based on these findings, we conclude that 2-MB is an appeasing pheromone in the brown rat. A better understanding of rats themselves would allow us to perform more effective ecologically based research on social skills and pest management campaigns with low animal welfare impacts, which might contribute to furthering the advancement of science and improving public health.