A novel study conducted at Oregon Health & Science University and the University of Auckland in New Zealand has revealed that a perfect molecular mixture present in male-emitted pheromone in musth (an annual period of sexual activity and increased aggression) dictates the sexual behavior of other surrounding male competitors and influences the female elephants mating interest.
The researchers argue that release of a specific proportion of two mirror images of the pheromone, frontalin, depends on whether the male elephant is mature enough and has reached a particular stage of musth.
"This study reveals the precision and specificity of inter-animal signaling possible. This is the first example, in mammals, of the use of this very precise signaling and ratio of enantiomers in signaling," said co-author L.E.L. "Bets" Rasmussen.
Enantiomers represent a pair of chemical compounds whose molecular structures are mirror images of each other. Frontalin, a pheromone discharged during musth by male Asian elephants from a temporal gland located between the eye and ear, takes two forms and is designated either with a plus or minus sign.
An analysis of the samples from six male elephants revealed that the pheromone is first detectable in the late teens, with the maximal production occurring over a 25-year life span. The frontalin enantiomers were found to be released in specific ratios depending on the age of the animal and stage of its musth. Any alteration in the ratio was found to elicit a different response from the potential female partner and other male elephants emitting the pheromone.
Until now, it has been assumed that elephants would make only one form of frontalin. The complexity associated with change of the frontalin's enantiomers ratio and the change in signal is something new that has been discovered.
When ovulating or "follicular" females, and females that were either pregnant or in a non-reproductive "luteal" phase were examined, a mild mating interest was seen when there was more of plus rather than minus form. A repulsive effect was observed when there were equal proportions of both forms.
Rasmussen added: "All of these responses and resultant behaviors are measurable in time. Not milliseconds, but seconds. We have a repertoire of follow-up behavior, such as trumpeting, running away and circling, that also can be counted and scored. Such information is translatable at the basic level to other animals," including humans.
The researchers hope to use the study's results to intensify the study further and possibly understand the mating behavior in other mammalian species.