Friday, October 3, 2014

Chemical Communication: The Language of Love

By: Dan Dixon

This is a story about smelling your friends.

Friday night is on the horizon. You can’t see it, hear it, or touch it, but you can smell it. You’ve had a hectic week burdened with traveling to and fro, paired with the daily stresses of being a nomad. It’s finally time to relax and share some quality communication with individuals of your own species. You’re mid-stride, maybe ten minutes from the local watering hole, when you begin picking up some low frequency vibrations. It sounds like a fiesta of sorts and the DJ is playing your favorite tunes. You naturally get excited and return a signal or two back towards the party to let them know you’re on the way. Fortunate for some, and unfortunate for others, you’ve been experiencing a constant, concentrated urine drip, similar to a leaky faucet, dispersing odorous compounds every which way. Even more flattering, a dense liquid is oozing from your face. The ooze source is an almost unnoticeable crater above the eye, coming from an area known as the temporal gland, symmetrically located on both sides. For you, it’s just that time of the year when your urine, dung, breath and parts of your face constantly emit chemical signals for a period of time ranging from a few weeks up to a few months. Chances are, and luckily for you, some females at the party will find you irresistible for reasons they can’t explain. And more often than not, they already got the cue that you’re in town for the night. This sounds like a typical Friday evening spent searching for potential mates, does it not? Did I mention you are a teenage male elephant in musth?

In this segment, I want to use this casual scenario as a model to introduce the ways in which Asian elephants rely on the signaling and reception of chemicals in reproductive settings. Take a step away from your computer screen and delve into the wrinkly skin of the teenage male so we can address some of the smells you’ve been emitting, and also those you’ve been receiving from potential companions.

Science has been working to empirically support the claims that Asian elephants depend on their ability to recognize, distinguish, process, and react to different chemicals signals. We’ve learned that the main uses of chemical signals have roots in reproduction and societal integration. To communicate from male-to-female, female-to-male, male-to-male, and female-to-female, both directly and indirectly, pheromones are emitted to reach the senses of another individual. Coming from the Greek words pherein (to carry) and hormone (to stimulate), pheromones are an extremely efficient way to communicate without the potential ambiguity seen in vocal, or body communication.

Not only seen in the elephant, pheromones are utilized throughout the animal kingdom. First appearing in 1959, bombykol was discovered in silkworms to act as a female-to-male attractive chemosignal. Since then, scientists have been discovering several different compounds used for different messages. It’s also not only used for sexual memos. Did you ever wonder how ants travel in synchrony to and from their home? Hint: They are not watching the feet of the guy in front. With scent producing glands all over their body, ants emit from 10 to 20 chemical odors with high hopes of reaching their fellow comrades. Their method of chemical detection is just as important to receive and process that information. That’s where antennae play a role. They are super sensitive and can distinguish direction from the concentration of chemicals in the air. The processing of these signals is almost instant, thus providing an extremely efficient method of communication. When thinking about writing this piece, I naively assumed that chemical signaling was a strictly terrestrial feat only utilized by land animals. Can marine wildlife also utilize the chemical sense to talk the love talk?

According to a paper on chemical signals in the marine environment, a variety of organisms rely on smells emitted from others to make conversation. For example, lobster urine carries important information for courtship, dominance, and individual recognition. Lobsters have been shown to locate odor sources by controlling three different water currents up to one meter in front of their crunchy self, then detecting minuscule variations of scents. The authors also discuss various methods used by fishes, marine mammals, mollusks and crustaceans. It is quite amazing how widely adapted these animals can be at communicating in their own distinct way. In elephants, we’ve observed their ability to use olfactory cues (smells), as their primary sense. So it would be totally reasonable for elephants to have adapted some sort of chemical language as well.

Let’s return to the party scenario. Remember, you’re a young, bull elephant secreting chemicals through liquid that vaporizes and disseminates into the air. As a male, you are sending signals to both males and females of your current status. Without saying a word, your signals are saying to the females, “I am ready to court you” and to the males, “Watch out, avoid me.” Your urine and dung are being dispersed and absorbed by the earth and plants. According to some elephant pee experts, in multiple increments your urine volume can reach up to 160 liters throughout the day. These secretions are being left behind for elephants traveling behind you, but also for individuals in the proximate area.

Just like the ant and the antennae, the receiving conspecific needs a way to detect and process the chemical signal. The signal passes through the vomeronasal organ (VNO) at the roof of the elephant mouth. By carrying the signal from its origin and placing the tip of their trunk to the VNO, the elephant can process the levels of different chemicals. This behavior, coined the flehmen response, can be used to measure the level of interest an elephant may have for that individual. The VNO then sends signals to the olfactory bulb and ultimately to the neocortex (for processing and motor purposes) and to the limbic system (for memory purposes). For more on the flehmen response and VNO organ, scope previous research assistant Dan’s blog here

So the party is going smoothly. You think you’ve found your mate, but as soon as you make your move, another mature, much-more-macho bull elephant enters the scene. Since you’re still young, your period of musth, maybe around a month, is much shorter than his, reaching up to three months. He’s been perfecting his style for years, if not decades. Your urine and secretions have a sweeter honey-like smell, but are still odorous and full of metabolites representing your heightened arousal and testosterone levels. However, his scent is obnoxious. It is dense and it reeks; he is producing 60x more testosterone than normal. Time and genetics are also on his side. Researchers have shown that older elephants, like him have a more attractive scent. His behavior is also more erratic and dangerous. That odor contains a much higher degree of a pheromone called frontalin; it’s attracting the most readily available females and keeping other males out of the way. As he approaches, you also retreat, knowing your power is no match. Unfortunately, your luck strikes out for the night and you hit the road riding solo once again.

I’m sorry to tell a story without a happy ending, but it’s realistic. The young male will prevail as future encounters change for the better. He is learning. It’s the same type of learning that the other large bull went through, completely necessary for social, complex creatures like elephants.  This is just a quick tale of how chemical signals are used though. I would have to write a seven volume novel series, and then adapt it into a screenplay to tell the full story of elephants and chemical communication. The vast spectrum of the chemical language still holds many questions, so future research will hopefully address some of those inquiries to really learn how these animals are connecting.

Below is a photo of Pepsi (currently in musth) with Buathong speaking their language.


Atema J. Chemical signals in the marine environment: dispersal, detection, and temporal signal      analysis. PNAS. 1995 (1) 62-66

Daniel JC. 1998. The Asian elephant: a natural history. Dehra Dun, India: Natraj Publishers.        306p.

Rasmussen LEL. 1998 Chemical communication: an integral part of functional Asian elephant       (Elephas maximus) society. Ecoscience 5:410-26.

Rasmussen LEL, Schulte BA. 1998. Chemical signals in the reproduction of Asian and African     elephants. Anim Reprod Sci 53:19-34.

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