formulate a hypothesis for how elephants respond to vibrations

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Vibrations from elephant calls and movements reflect distinct behaviors, study says

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• Elephants create inaudible seismic waves when they move or “rumble” that complement the audible sound we hear and that researchers can detect using geophones placed in the ground.
• In a new study, elephants walking or calling through low-frequency rumbles created distinct seismic signals the transmission of which was affected by both local geological structure and low-frequency human-generated noise.
• The research suggests that elephants not only generate these distinct vibrations through their different activities, but can also perceive the difference from at least one kilometer away, suggesting they are using the vibration patterns to communicate.

The well-known trumpeting call of an elephant indicates anger or alarm . The more common but less familiar rumbles are a range of low-frequency sounds that elephants use to communicate different types of messages to one another.

Scientists have found that rumbles travel through both the air and the ground. These low-frequency calls create seismic waves—vibrations occurring underground and along the earth’s surface—which, depending on the soil type, can travel farther than the counterpart waves we hear moving through the air.

A new study has found different elephant behaviors created distinct seismic signals and that both the local geological structure and low-frequency human-generated noise may affect transmission of these signals.

Ground versus airborne sound waves

When an elephant, rabbit, or person walks, we create seismic waves, the heavier and faster the walk, the greater the strength of the wave. Seismic wave transmission is also affected by physical factors, such as the underlying soil type and other noises in the same frequency range.

In areas with minimal human seismic noise, the frequencies around and below 20 Hz characteristic of elephant vocalizations are relatively noise-free .  Noises at this frequency, also known as infrasound, are generally too low for us to hear.

Research by Caitlin O’Connell-Rodwell of Stanford University has shown that elephants in Namibia can both detect seismic signals and distinguish alarm calls made by neighboring groups from unfamiliar ones made by groups in Kenya.

Use of seismic signals to classify behavior

The new study , published this month in Current Biology , builds on earlier research by applying seismological modeling software that incorporates the local geological information and computer algorithms to produce more accurate estimates of the propagation of seismic waves, specifically those produced by elephants.

Researchers from the University of Oxford’s Department of Zoology and Earth Sciences and the Kenyan NGO Save The Elephants examined whether  they could classify elephant behaviors by monitoring the vibrations that their movements send through the ground.

To do this, they first recorded vibrations generated by wild elephants in Kenya during different behaviors, mainly walking and calling. They filmed the elephants during recordings and later synchronized the video with the recordings to allow them to visually confirm that the vibrations originated from elephants during various behaviors.

They positioned a geophone —a device that records ground movement (velocity) and converts it into voltage—near a focal elephant.  The deviation of the voltage measured by the geophone from the natural background voltage is called a seismic response and is typically used for analyzing the earth’s structure.

In this case, the researchers analyzed the seismic response from elephant behaviors using a source function—“the force strength and pattern generated by the elephant ‘at the source’”—generated by the focal animal during each behavior type.

“We applied a technique to extract the source signature of the elephants from our recordings,” co-author Tarje Nissen-Meyer, a geophysicist at the University of Oxford, UK, told Mongabay-Wildtech. “This source function is then independent of geology and propagation effects and a direct indicator of both the size of the force and temporal evolution, i.e. for running, rumbling, regular walk, individuals versus herds. This is the crucial step towards building a classification for different behaviors.”

The researchers combined the source functions, the type of geological substrate—hard gneiss rock or three types of sand—found at the site, the amount of other noise, and seismological modelling software to estimate two factors needed to classify different behaviors. The models :  (1)  estimated how far these seismic signals can travel and (2) extracted the seismic signal actually produced by the elephants, independent of geology and other seismic noise.

How seismic waves travel

The researchers found that walking and vocalizing generated distinct seismic signatures, with larger animals producing greater downward force that travels farther. They also found that other noise and soil type affected their ability to distinguish the patterns over long distances. Vibrations travel farther through sand than through hard rock and, not surprisingly, when little other noise is present to interfere.

In their paper, the authors state, “Differences in elephant behavior caused detectable changes in source function properties, which remained  distinguishable during modelled seismic wave propagation up to 1000 metres regardless of the noise level and terrain type.”

O’Connell-Rodwell, who was not part of this study but has studied elephant seismic communication for nearly 15 years, said the results served as an important validation of what she and colleagues have previously published in this field. Her team’s seismic census studies suggest that elephants have a signature walk that is more similar to humans and distinct from lions, rhinos and ungulates and that all species have a signature seismic signal while walking.

“The level of detail that can be gained from recording footfalls using geophones would even pick out a musth bull from other male elephants simply because of their exaggerated gait,” O’Connell-Rodwell said. “This has huge potential for monitoring remote waterpoints, particularly those that do not have heavy animal traffic, as the math would be simpler to sort out and quantify species, number of animals visiting and time of day.”

In the current study, the researchers were surprised to find that, for their set of source functions, the elephants’ vocalizations produced greater seismic force and traveled farther than those from walking.

“We found that the forces generated through elephant calls were comparable to the forces generated by a fast elephant walk,” lead author Beth Mortimer of the Universities of Oxford and Bristol, UK said in a statement, “This means that elephant calls can travel significant distances through the ground and, in favorable conditions, further than the distance that calls travel through the air.”

Nevertheless, the authors note, the capacity of car engines, heavy machinery, oil exploration, and other human noise in the 20–25 Hz frequency range to interfere with the transmission of seismic waves could increasingly impede animals’ seismic communication.

The authors suggest that seismic detection of rapid running by an elephant could be used to help assess an immediate poaching threat in remote areas with low levels of seismic noise. They acknowledge that deploying multiple geophones and more data and testing are needed to develop such near-real-time monitoring of elephants.

For example, a threatened herd may run but may instead bunch together to protect their young. Further research and development are also needed to determine where to position the geophones for a given area’s elephant population and how to distinguish an elephant running when chasing another in a test of dominance, approaching water, or in play, from one that is threatened.

The research team’s modeling and signal-processing techniques and the software they used are entirely open-source (they developed the seismic modeling approach), Nissen-Meyer said, and they will remain open-source for anyone to use.

He emphasized that their results were made possible by a cross-disciplinary approach to research and added, “I am convinced that this is increasingly crucial for breaking into new territory and demands an open mindset not only across disciplines, but also for novel developments in methods and techniques.”

Mortimer, B., Rees, W. L., Koelemeijer, P., & Nissen-Meyer, T. (2018). Classifying elephant behaviour through seismic vibrations.

O’Connell-Rodwell, C. E. (2007). Keeping an “ear” to the ground: seismic communication in elephants.  Physiology ,  22 (4), 287-294.

O’Connell-Rodwell, C. E., Wood, J. D., Kinzley, C., Rodwell, T. C., Poole, J. H., & Puria, S. (2007). Wild African elephants (Loxodonta africana) discriminate between familiar and unfamiliar conspecific seismic alarm calls.  The Journal of the Acoustical Society of America ,  122 (2), 823-830.

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Picking up good vibrations: Feeling the beat through the elephants feet

Iconic and intelligent creatures, elephants continue to fascinate curious onlookers and scientists alike. Now a new Oxford University collaboration with Save The Elephants has shown that elephant behaviour can be determined in a new way: through the vibrations they create.

The findings of the study, published in the journal  Current Biology , offer a new way to detect elephants and discern their behaviour without having them in sight. It also has the potential to provide real-time information on elephant distress and poaching threats in remote locations.

Researchers from the University’s Department of Zoology and Earth Sciences worked together with Save The Elephants to develop an innovative way of classifying elephant behaviours by monitoring the tremors that their movements send through the ground. 

To capture the information, the two lead scientists, Dr Beth Mortimer and Professor Tarje Nissen-Meyer, along with Masters student Mr William Rees and Dr Paula Koelemeijer, used small sensors called ‘geo-phones’ to measure the ground-based vibrations generated by elephants in Kenya’s Samburu National Reserve. The study relied on the application of cutting-edge seismological techniques, commonly used to study earthquakes and dynamic processes inside Earth.

The team also performed an active but complementary experiment wielding a sledge hammer against the ground, which allowed them to generate and measure a controlled vibration, and recorded the sound of cars, people hopping up and down, planes flying overhead and a variety of other noises that contributed to the signals scientists might pick up when recording elephants. 

Due to their large size, it is perhaps unsurprising that elephants generate vibrations through their normal movements. But, they also produce detectable seismic vibrations through low frequency vocalisations – known as ‘rumbles’, which were studied in the research, as well as trumpets.

These movements were then compared with the airborne and ground-based vibrations that they produced. By distilling the vibrations caused by elephant behaviour from background noise, and by quantifying how far and wide these sounds travel through the ground, this study demonstrates that seismological techniques are well suited to solving problems within conservation monitoring.

Vibration detection is a forgotten sense in the study of many animals, but is particularly important for elephants,’ says Dr Mortimer. Due to their large size, it is unsurprising that elephants generate vibrations through their normal movements. But elephants also produce detectable seismic vibrations through low frequency vocalisations – otherwise known as ‘rumbles’.

Prof. Tarje Nissen-Meyer adds, ’Our findings bore out of multi-disciplinary research across traditional domain boundaries, relying on novel seismological methods.’

Computer models developed in this research indicate that these vibrations are detectable beyond what is audible, suggesting that elephants can use ground-transmitted information to know the whereabouts of the rest of the herd, even over several kilometres, depending on terrain type. 

Scientists and conservationists are increasingly worried about the effects of noise caused by humans. By preserving wild landscapes, elephants can continue to detect the signal above the noise. ‘The impact of other noise on this mode of communication mode is particularly worrying given the increased levels of human-generated seismic vibrations in remote locations,’ says Dr Beth Mortimer.

Save The Elephants’ CEO, Frank Pope comments: ‘Legends and folklore have long spoken about the way elephants can not only communicate across long distances, but also detect other events that shake the ground like far-off thunder. This study marks a new phase in trying to understand the nature of the vibrations elephants produce and how they might be used by elephants themselves. Along the way it is opening our eyes to the challenges posed by human-generated noise in an increasingly crowded landscape.’

 ‘We hope to build on these initial findings to develop a comprehensive approach for monitoring and understanding the behaviour of large mammals in these pristine, changing and fragile environments, and examine whether elephants can localise not only their peers or other species, but also environmental factors such as water’ adds Nissen-Meyer.

By preserving wild landscapes, elephants can continue to detect the signal above the noise.  

Read the full paper in Current Biology here.

Vibrational Communication in Elephants: A Case for Bone Conduction

• First Online: 30 November 2019

Cite this chapter

• Caitlin O’Connell-Rodwell 9 , 10 ,
• Xiying Guan 9 &
• Sunil Puria 9 , 11  

Part of the book series: Animal Signals and Communication ((ANISIGCOM,volume 6))

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We present new physiological data on bone conduction hearing from cadaveric temporal bone ears of an elephant. We discuss the results in the context of the elephant’s ability to detect and interpret ground-borne vibrations as signals and compare with similar measurements in a human cadaveric temporal bone ear. Large ossicles are potentially indicative of superior bone conduction hearing, and elephant ossicles are the largest among terrestrial mammals. Using 3D laser vibrometry, we measured stapes velocity in each x , y , z planes and the promontory velocity to determine relative velocity as an indication of vibrational input to the cochlea via the footplate. Since elephant ossicles are at least seven times the mass of human ossicles, we compare the sensitivity of both species to vibrations in the frequency range of 8–10,000 Hz and report that elephants have up to an order of magnitude greater sensitivity below 200 Hz, indicating a heightened sensitivity to bone conduction hearing in comparison to humans.

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O’Connell-Rodwell, C., Guan, X., Puria, S. (2019). Vibrational Communication in Elephants: A Case for Bone Conduction. In: Hill, P., Lakes-Harlan, R., Mazzoni, V., Narins, P., Virant-Doberlet, M., Wessel, A. (eds) Biotremology: Studying Vibrational Behavior . Animal Signals and Communication, vol 6. Springer, Cham. https://doi.org/10.1007/978-3-030-22293-2_13

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Ear to the ground: Locating elephants using ground vibrations

Researchers from the University of Oxford, Mpala Research Center and Save the Elephants, have used a combination of acoustic microphones and seismometers to locate elephants.

In this novel study, published today in The Journal of the Royal Society Interface , researchers managed to accurately determine elephant locations by measuring the vibration of the ground caused by their rumbles, which are low frequency calls. To do this, they used seismometers, which are seismic sensors typically used for measuring earthquakes and explosions.

Seismic waves pass through lots of different solid materials between source and sensor, unlike the acoustic waves. It was a surprise that the seismic sensors worked just as well as the acoustic sensors to localise the elephants, and in some cases they worked even better

This interdisciplinary research, created in collaboration with computer scientists, earth scientists, conservationists, and biologists, used data gathered in Kenya, and is the first study to use seismometers to get locational information about elephants in the wild. Acoustic and seismic equipment was set up around a watering hole known to be frequented by elephants at the Mpala research center in Kenya, and paired with camera traps to provide additional data. Researchers discovered that the seismic dataset led to a more accurate localisation of elephants than the acoustic dataset.

Previous work has shown that seismic recordings can be used to differentiate between elephants’ activities such as walking, running and calling. But seismic monitoring also provides information about other animals and their activities. In future work, the team hopes to develop ”listening rules” to detect what wildlife is close to these sensors and what they are doing, all based on their seismic “footprints”.

Dr Michael Reinwald , postdoctoral researcher at Oxford’s Department of Zoology , said: 'Seismic waves pass through lots of different solid materials between source and sensor, unlike the acoustic waves. It was therefore a surprise that the seismic sensors worked just as well as the acoustic sensors to localise the elephants, and in some cases the seismic systems worked even better.'

From a conservation perspective, using seismic sensors alongside acoustic systems offers an alternative, and potentially more accurate, way of assessing situations. Where acoustic recordings would be influenced by rain, wind, and both human and animal activity, seismic monitoring would be impacted by other factors, such as geology and sensors are buried under the ground.

This is useful because it allows conservationists to have more data on where elephants are in different scenarios. Knowing whether or not elephants are present in protected areas, or if they’re going into environments with higher risks, allows for reactive responses, and can limit human-elephant conflict.

PI Dr Beth Mortimer from the Department of Zoology said, “This study is important as it shows that seismic information from elephant rumble calls is just as useful as acoustic information for locating elephants. This opens up further questions about how the elephants might be using seismic rumbles to communicate with each other in the wild.”

Moving forward, this allows researchers to develop novel and innovative ways to monitor elephant movement. This real time detection and localisation of both elephants and other wildlife will allow for more appropriate anti-poaching intervention and limiting wildlife-human conflicts.

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Elephants turn to seismic communication

It is well known that elephants “speak” to each other but they might also communicate through seismic waves according to geophysicists. Caitlin O'Connell-Rodwell, Roland Günther and Simon Klemperer at Stanford University have shown that elephants can produce low-frequency waves that are capable of travelling more than two kilometres through the ground ( Geophysical Research Letters 31 L11602). Seismic communication is used by a variety of animals including arthropods, amphibians and small rodents.

Elephants communicate primarily through sounds or vocalisations known as “rumbles”. These rumbles have fundamental frequencies in the infrasonic range below 30 Hertz, which means that they cannot be heard by humans, although the harmonics of the fundamental frequency are audible. The Stanford team has shown that these rumbles can also act as a source of Rayleigh waves that can travel through the ground.

Following on from previous work by O’Connell-Rodwell, the Stanford geophysicists studied the propagation of Rayleigh waves produced by three trained African elephants using a line of 57 geophones that began just outside the elephant enclosure and extended out to about 175 metres. They also used three microphones to measure acoustic signals in the air. Using computer models, the scientists estimated that the seismic signals produced by the elephants could travel distances up to about 2.2 kilometres through the ground, compared with only 1-2 kilometres for through the air.

“It is possible that elephants use ground waves to communicate during times when acoustic communication is not ideal, as well as over short distances to supplement acoustic communication,” Günther told PhysicsWeb .

O’Connell-Rodwell and colleagues believe that elephants sense the underground vibrations through special receptors in their feet and trunks. The team is now studying elephants at Oakland Zoo in California and in the Etosha National Park in Namibia.

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Stanford University School of Medicine blog

Eavesdropping on elephants in the name of research

Listening in on others' conversations generally isn't polite, but if you're  Caitlin O'Connell-Rodwell , PhD, eavesdropping isn't rude -- it's research. O'Connell-Rodwell, an adjunct professor in Stanford Medicine's Department of Otolaryngology-Head and Neck Surgery, investigates hearing (and what happens when it goes awry) by eavesdropping on the vocalizations and vibrations that elephants make when they communicate.

Mice are the animal models of choice for many researchers, but O'Connell-Rodwell has found that if you want to study human hearing, elephants are the way to go. The  frequencies detected by human ears are more similar to those heard by elephants than that of mice (see audiogram here), which is why O'Connell-Rodwell studies elephants to investigate vibrations and in communication in large mammals.

To learn more about this research, Stanford writer Melinda Sacks flew nearly halfway around the world to become a volunteer researcher on O'Connell-Rodwell's team. She chronicles her experience in a recent Stanford Magazine story :

The tiny trunk is about the thickness of my index finger, dark gray with a tinge of pink around the tip. It is as inquisitive as it is tentative, stretching toward us as we lean back to avoid direct contact. We hold our breaths, suppressing squeals of delight, as the brand-new baby elephant tries to touch us through the viewing 'window' of the concrete bunker where we are hiding.

Every summer for nearly a quarter of a century, O'Connell-Rodwell has made Mushara, a remote region on the eastern edge of Namibia's Etosha National Park, her home. During this time, she's made some incredible discoveries, as Sacks explains:

O'Connell-Rodwell was the first to discover the way elephants communicate through vibrations in the ground. She also showed that elephants 'listen' to these vibrations with either special sensors in their feet and at the tips of their trunks or through bone conduction.

The research team captures elephant vocalizations and vibrations -- a form of elephant communication that includes vocal rumbles, trumpets, ear flapping, trunk gestures, body position and body stance -- via highly sensitive microphones hidden in rock piles near their water holes.

Much of O'Connell-Rodwell's research focuses on elephant communication and how it can inform our knowledge of hearing, hearing loss and deafness, but there are many reasons to learn about and protect elephants.

"No matter where you come from, spiritually or socioeconomically, there is some sense of pride that you share this earth with these creatures," O'Connell-Rodwell answered when Sacks asked her why people should care about African wildlife. "We can save it or destroy it. It's in our power. It shouldn't be, but it is."

The entire piece is worth a read.

Photography by O'Connell & Rodwell

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How the elephant gets its infrasound.

Blowing air through a pachyderm’s larynx offers hints to low-frequency communication

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By Susan Milius

August 2, 2012 at 2:04 pm

Elephants don’t purr so much as sing when they unleash low-frequency rumblings at friends and foes kilometers away.

Too low for humans to hear, the infrasonic components of elephants’ calls have at times been attributed to a process similar to a cat’s contented thrum. But new measurements made by blowing air through the voice box, or larynx, of a deceased zoo elephant suggest that the mechanism is actually a (much bigger) analog to a person speaking or singing.

Cascades of fast, active muscle contraction give cats their purr. Biologists have speculated that some similar muscle twitching creates the deep throbbing of elephant infrasound. But elephants can get their rumbles going just by exhaling air through their vocal tracts, says Christian Herbst of the University of Vienna. With the new demonstration of air power, Herbst says, “there’s no need to go into the purring hypothesis.” He and his colleagues make their case for superlow elephant song in the Aug. 3 Science .

The part of an elephant’s call audible to humans travels only about 800 meters through air, but the infrasonic tones can reach up to 10 kilometers under ideal conditions. The noise can vibrate via the ground too, theoretically going much farther.

“We really do not know that much about the specific characteristics of elephant sound production,” says Peter Wrege of the Cornell Lab of Ornithology, who directs a project monitoring hard-to-see forest elephants in Central Africa by listening for infrasound.

Too true, Herbst says. He’s recorded his own larynx in action by threading equipment into his mouth, but he’s not going to try that with any big mammal.

“The elephant would just close his mouth and say, ‘Thank you for the snack,’” Herbst says. “If you’re lucky.”

He and his colleagues made arrangements with a zoo to extract the larynx of an elephant within just a few hours of its death. An elephant larynx has strips of tissue lying across the airway called vocal folds, just as humans and other mammals do. As air rushes up out of the lungs, the folds separate and then touch again, creating puffs that set the whole voice mechanism into action. To visualize their vibrations, Herbst says, “think of a flag in the wind.”

Elephants have vocal folds about eight times the size of a human’s, and greater size lowers the sound of the vibrations. If people had elephantine vocal folds, humankind might be speaking infrasound too.

The disembodied larynx in the lab could be re-creating sounds similar to an elephant’s infrasonic blast in the lowest-pitched vibration, called the fundamental frequency. But the test didn’t capture all of the complexities of a real call from a living animal with an intact head.

“Elephants have these really interesting anomalies,” says Caitlin O’Connell-Rodwell of Stanford School of Medicine’s otolaryngology department. A large cavity opens in the front of an elephant skull, with some deposits of dense fat a bit like the acoustic structures in marine mammals. So vocal folds flapping in the wind might be only the beginning of the story, she says.

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This video follows ecologist Caitlin O'Connell-Rodwell, who is studying how elephants can communicate over long distances using low-frequency sounds that travel both in the air and through the ground.

O'Connell-Rodwell, a research associate at Stanford University School of Medicine, has been studying elephant communication in Etosha National Park in northern Namibia for decades. She observed that elephants seem to detect vibrations in the ground with their feet and trunk. Using amplifiers, speakers, geophones, and video cameras, she designed an experiment to test how elephant herds respond to an alarm call that elephants produce to warn others of nearby predators.

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Caller ID in the wild: African elephants communicate by ground vibration, Stanford researcher finds

May 29, 2007 - By Tracie White

STANFORD, Calif. - In the vast expanse of African grasslands, wild herds of migrating elephants have learned to communicate with each other by listening with their feet to vibrations in the ground. Now a Stanford University School of Medicine researcher has found their seismic communication system is so sophisticated the elephants have their own version of "caller ID."

"It's a much richer communication system than we thought," said Caitlin O'Connell-Rodwell, PhD, an ecologist who initially discovered this underground communication system 14 years ago while observing wild elephant herds in northern Namibia.

O'Connell-Rodwell has written about this journey of scientific discovery in her book, The Elephant's Secret Sense: The Hidden Life of the Wild Herds of Africa , published in March. Her newest study on the topic, which measures the ability of elephants to recognize whether an underground message is delivered by a familiar or unfamiliar source, will be published in August in the Journal of the Acoustical Society of America.

"I see this is going to be a lifetime journey," said O'Connell-Rodwell, a research associate in the school's otolaryngology department . She hopes to draw analogies between humans and elephants in research conducted with people and hearing implants at Stanford because the hearing-impaired population is "much better at feeling vibrations," she said.

O'Connell-Rodwell's journey into discovering this secret sense of elephants began with a simple observation. While hunkered down in a bunker observing family herds of elephants next to a favorite watering hole at Etoshia National Park in northern Namibia in 1992, she noticed a curious behavior. Suddenly the entire herd would freeze, ears flattened to their heads. Each enormous beast would lean forward up on tiptoes, sometimes raising one foot in the air.

Caitlin O'Connell-Rodwell

"When elephants are listening with their ears, they have huge, extended ears," O'Connell-Rodwell said. But in this instance, the ears remained flat. She knew about the process of listening through limbs, a phenomenon known as "seismic communication" in insects, having spent endless hours in a small soundproof chamber recording the seismic love songs of Hawaiian planthoppers when she worked toward a master's degree in entomology. O'Connell-Rodwell became convinced the elephants were listening to seismic vibrations through the earth, but it's taken her years of painstaking scientific research to convince the rest of the world.

"It took a long time for this idea to gain momentum," said O'Connell-Rodwell, who also works with her husband Tim Rodwell in San Diego to co-direct a nonprofit conservation organization, Utopia Scientific . "People weren't thinking that larger mammals could do this. We've had to prove ourselves each step of the way."

Past studies by O'Connell-Rodwell and colleagues have shown that when African elephants stomp and rumble as a predator approaches, other distant elephants can get the news by feeling the ground ripple through their feet or trunk. This may have the direct or indirect effect of alerting other elephants of potential predators and other threats. Other seismic messages, such as distance thunder rumblings, could also let elephants know when and where the rains will arrive, explaining their uncanny ability to move hundreds of kilometers in the right direction to get to the green growth that the rains will bring.

The new study suggests that not only can the elephants receive and interpret underground calls, but they can distinguish between specific callers.

Working with senior author Sunil Puria, PhD, Stanford consulting associate professor of mechanical engineering, to conduct the study, O'Connell-Rodwell and colleagues converted previously recorded alarm calls from two different elephant herds into seismic vibrations and sent them to a herd of elephants at the watering hole at Etosha National Park. The recorded alarm calls were very similar, both low-frequency vocalizations that lions were approaching, but one was sent by elephants living in the same park as the study group in Etosha, and the other taken from elephants living far away in Kenya.

"The elephants at the watering hole responded only to the familiar calls," O'Connell-Rodwell said. "They would freeze, clump into tighter groups, leave the watering hole earlier. I expected some response to the unfamiliar calls, but they didn't appear to care about it at all.

"I wasn't expecting their ability to be that subtle," she said. "Maybe I underestimated it."

O'Connell-Rodwell has spent most of her summer months for the past 14 years hidden in the same dank bunker watching the same group of migrating elephants at the watering hole in Etosha National Park. Over the years, she's been stalked by lions who have climbed up on the bumper of her pickup truck when she was sleeping in the back and, once, nearly climbed headlong into her bunker. Still, she writes about her bunker and her herd of elephants with continuing appreciation and awe.

"The bunker is wonderful," said O'Connell-Rodwell, who camped out alone for weeks at a time patiently observing the elephants' behavior. She loved "listening to the night sounds, the lions roaring, the hyenas calling."

Her wonder at these enormous beasts of Africa fills her book. She writes about the "tiptoeing elephants" with their "vaudeville eyelashes almost comical in length" and "giant stethoscope feet" with love and admiration.

"We still have this very special window into their society but I don't know for how much longer," O'Connell-Rodwell said. "I grew to understand the elephant's society. How they treat each other. How they care for each other. I watched their relationships."

She grew to know which of the elephant bulls were the bullies, which the gentle giants. She even named them. One bull with a long, scraggly, gray tail, dubbed "Willy Nelson," is "a little bit of an outsider, but well-respected," she said. One of the matriarchs dubbed "Margaret Thatcher" is "somewhat of a tyrant but takes care of her own."

O'Connell-Rodwell's passion for elephants began all those years ago, with an initial serendipitous job offer. During a nine-month trip to Africa with her husband, she was offered a job helping Namibian farmers come up with new ideas for scaring away rampaging, wild elephants that could devour a year's worth of crops in one day. She's still working on new ideas as the elephants continually adapt to her plans to scare them off with car alarms or underground warnings.

"They're just too freakin' smart," she said.

She'll be heading back to Africa once again on June 8 for two months of elephant observation.

O'Connell-Rodwell works with principal investigator Robert Jackler , MD, professor and chair of otolaryngology. She has received funding for her elephant studies from the National Geographic Society, the U.S. Fish and Wildlife Service, the National Science Foundation, the Seaver Institute, TRAFFIC International and several Stanford University grants including including one Bio-X award with co-principal investigators Simon Klemperer, PhD, professor of geophysics, and Robert Sapolsky , PhD, professor of biological sciences and of neurology and neurological sciences.

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