Life expectancy of chemical signals

Volatiles evaporate, and signals become weaker over time. In mixtures, evaporation of the more-volatile compounds can change the quality of the odor and the range over which it can be detected. This means that decaying and 

F erkin and Johnston (1995 a) aged anogenital area scent and odor from the posterolateral region in meadow voles Micmtuspennsylvanicus) for 15 minutes to 30 days. Males preferred female to male anogenital odor if it was 10 days old or less. Females preferred male to female anogenital odor if its age was 25 days or less. Both sexes preferred posterolateral odor of males to that of females if it was up to 1 day of age. In a second experiment, both sexes preferred fresh odors from either source over the same scents that were older. In conclusion, information about sex may get lost with the age of the scent mark. 

Pheromones in urine will suffer degradation, hydrolysis, oxidation, and ultraviolet radiation effects. For example, the (Z)-7-12-acetyl derivative in elephant urine will gradually hydrolyze (Rasmussen, 1988). In this case, the lipoprotein carriers of the elephant acetate may also determine the life time of the signal besides serving to filter and select odorants, confer specificity, and play a critical role in the transport and transfer of an active ligand to the vomeronasal organ (Rasmussen and Schulte, 1998). 

Keeper substances and commonly used marking substrates such as clay and wood can extend the fade-out time of the signal. Licking or exhaling on scent marks or the body surface of another individual liberates on-demand odors . Alberts (1992a) characterized such signals as having multiple rise times. 

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