For young male elephants, youth is so sweet you can actually smell it.
Researchers have learned that male Asian elephants that have just begun puberty signal their innocence through secretions that smell like honey.
The sweet secretions drip from an olfactory gland between their eyes and ears and make their role clear to other elephants, preventing competitive attacks from their bigger male counterparts.
"The secretions contain acetates, which are present in many flowers," said Bets Rasmussen, a biochemist at the Oregon Graduate Institute of Science and Technology in Beaverton. "The sweet smell tells females that an immature male still has some growing up to do and informs aggressive mature males that they pose no threat."
Cited by Ancient Poets
Rasmussen points out that Hindu poets actually recorded the honey-like smell of young male elephants thousands of years ago. One verse describes the arrival of bees to "gather sweetness from the temples of [young] elephants."
Recently, Heidi Riddle stumbled across the same observation as she herded a young Asian male elephant into the barn at the elephant sanctuary she runs with her husband in Greenbrier, Ark.
The male elephants in her sanctuary had entered musth (pronounced "must"), an annual period of heightened sexual activity. Riddle noticed an immature 11-year-old Asian male elephant was secreting a fluid from its gland.
"I rubbed some off onto my hand and was really surprised — it was a totally different smell," Riddle said. "The first thing that struck me is it smells like raw honey. I thought that was kind of unusual."
Riddle contacted Rasmussen, who soon began investigating the scent. She analyzed samples from Riddle's captive elephants and from wild Asian elephants in south India. Then, with Indian elephant researcher V. Krishnamurthy, she watched how other elephants reacted to the scent in the wild. The three researchers published their results in today's issue of the journal Nature.
For the most part, older males showed little reaction when they were in proximity of the sweet secretions of male youths. ("They could care less," Rasmuseen observed.) But when younger males smelled the rancid secretions of adult males, they stayed clear.
Seeking Strong, Smelly Male
Young male elephants may smell sweet, but it's the rancid secretions of sexually ready adult elephant males that attract the females.
"To people, it's a foul smell, but female elephants are very interested," said Rasmussen. "Some even go up to the males and touch the glands of the male."
Rasmussen explains female elephants likely interpret the pungent smell to be a sign of a healthy, virile bull.
Rasmussen's past studies show that females, too, communicate by odor. When they're ready to mate, female Asian elephants release a pheromone in their urine. Male elephants then dip the finger-like projection at the tip of their trunks into the urine puddles and become aroused by the odor.
Interestingly, the pheromone in the female's urine, a chemical called (Z)-7-dodecen-1-yl acetate, is also used as an attractant among more than 100 insects.
Other work has shown that chemical communication is an important tool among many animals. Meadow mice release hormones after mating that activate behavior patterns that help bond the pair for life. Queen bees emit a pheromone that helps keep the peace among the hundreds of male worker bees at her hive.
And research with people suggests we, too, can detect chemical signals using two tiny pits inside the nose. One 1998 study claimed the chemicals play a role in synchronizing the menstrual cycles of women who live together. However, some remain skeptical and believe genetic mutation long ago deprived humans of the ability to emit and respond to pheromones.
Rasmussen, who was surprised to find that Asian elephants emit a scent just to convey youthful innocence, believes there's a lot more to learn about the invisible language.
"When it comes to chemical signals, I think we've barely touched the surface," she said.