An Alarm Pheromone May Be Released by Defeated Competitors: A Possible Indicator of Danger

Abstract

Among many species, the establishment of hierarchical relations contains a highly ritualized behavioral context accompanied by the delivery of volatile agents, namely ketones and aldehydes, into environment. These substances act as signals contributing to defining and maintaining social hierarchies. Among mammals, some volatile compounds are released into the environment to report the presence of danger or conflict to conspecifics. For example, rats release an alarm pheromone, 2-heptanone, through their urine when subjected to physical stress. However, it is unknown whether some similarity occurs in human being, in spite that many possible alarm compounds have been identified in human fluids, including 2-heptanone. Contact sports may represent a situation of psychosocial interaction in which some hierarchy is established at the end of the contest. In such a case, the first match in martial arts competitions represents a natural model that is seemingly useful for studying alarm conditions in humans since there are two outcomes, winner and non-winner and after a stressful situation represented by contest, some kind of hierarchy is established. The present study measured urinary concentrations of 2-heptanone using gas chromatography-mass spectrometry and applied anxiety measures (State-Trait Anxiety Inventory, STAI) in a sample of healthy student athletes. Compared with martial-arts winners, the characteristics of the non-winners included an increase in their urinary 2-heptanone content (F2,18 = 5.541, p < 0.01), with no changes in anxiety scores (STAI-T: F2,18 = 0.052, p = 0.949; and STAI-S: F2,18 = 1.083, p = 0.360). The production of this ketone seems to be related with metabolic routes of fatty acids involving the participation of the so called stress hormones that may lead to an increase in the lipolysis of fatty acids and production of their metabolites, and among them, 2-heptanone. The increased release of 2-heptanone at the end of the match in non-winners may be interpreted as the release of an alarm signal that indicates imminent danger, similar to the occurrence in other species.