Asian elephants are adept at changing the pheremone’s makeup.

Like Christmas, musth comes but once each year. And for the male elephants that go through it, that’s a good thing. For during musth, a period of heightened sexual activity marked by extremely high testosterone levels, males become very aggressive and can work themselves into a frenzy. (The term, first described in Asian elephants, is derived from a Persian word meaning “drunk”.)

Among other things, during musth liquid streams from the animal’s temporal glands, between the eye and the ear. It contains a pheromone, frontalin, that serves as a chemical signal to other elephants.

Now, research by Bets Rasmussen of the Oregon Health & Science University and colleagues in New Zealand shows that male Asian elephants can control this signal as they age and even during a single musth period.

They are adept biochemists, changing the makeup of the pheromone over time.

Molecules of frontalin come in two mirror-image forms, called enantiomers. The researchers, who analysed more than 100 samples of temporal gland secretions, had thought that the liquid would contain only one of the forms. “To our utter surprise we found both,” she said. “This had never been seen before in mammalian pheromones.” The finding is described in the journal Nature.

What’s more, the researchers found that the ratio of the two forms changed with age. Young males contained significantly more of one form (designated “plus”) than the other (“minus”), but as the animals matured the mix of enantiomers became even.

Highly “plus” frontalin had little effect on other elephants, but a one-to-one blend repulsed males of all ages and attracted ovulating females. So the makeup enables other elephants to gauge how mature the frontalin-producing elephant is.

Rasmussen said the finding might help in conservation. Synthetic frontalin in the proper proportion may prove useful to control elephant movements.

The work should also help scientists study the function of receptors that detect frontalin. In fact, Rasmussen said, elephants are a great model for studying olfaction. That’s because they have two organs and billions of cells devoted to it, she said, but also because their responses are easily observed.

“With a laboratory rat, you can’t tell if he’s sniffing,” Rasmussen said. “But when an elephant is reacting to something, it’s pretty clear.”