Rats and mice have a highly developed vomeronasal system and use ultrasonic communication extensively. Much information that is important in the world of the rat or mouse is lost to the investigator. These ultrasonic and chemical signals convey important information to other rats or mice about environmental dangers and how individuals differ from each other. Males and females will respond differently to the signals from conspecifics (e.g., the scent of a male rat might provoke an aggressive response in another male but induce sexual motivation in an estrous female).