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 bit.ly/1E6EFcn.
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.
Sources
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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