PART 5
Read the following text for questions 30-35.
Elephants’ Early Warning System
A new study shows that elephants may communicate with other herds through seismic vibrations.
Few sights in nature are as awesome as a six-ton elephant guarding her baby from a hungry predator. Rather than retreat, the threatened mother is likely to launch a mock charge - a terrifying display of ground stomping, ear flapping and frantic screaming designed to frighten off lions and hyenas.
But elephant researchers have discovered that there is more to a mock charge than meets the eye. According to a new study in the Journal of the Acoustical Society of America (JASA), foot stomping and low-frequency rumbling also generate seismic waves in the ground that can travel nearly 20 miles along the surface of the earth. More astonishing is the discovery that elephants may be able to sense these vibrations and interpret them as warning signals of a distant danger.
'Elephants may be able to detect stress from a herd many miles away,’ says Caitlin O'Connell-Rodwell, an affiliate of the Stanford Centre for Conservation Biology. 'They may be communicating at much farther distances than we thought,’ adds O'Connell- Rodwell, author of the JASA study.
In the early ‘90S, O'Connell-Rodwell began to suspect there was more to long- distance elephant communication than airborne rumblings alone. ‘I started working with elephants in Etosha National Park in 1992,’ she recalls. ‘I was observing them at a drinking hole when I noticed this strange set of behaviours. They would lean forward, pickup one leg and freeze - or begin stomping their feet for no apparent reason.’ She theorized that the elephants were responding to vibrations in the ground from approaching herds. ‘When I returned to the University of California at Davis, I teamed up with my Ph.D. adviser, Lynette Hart, and geophysicist Byron Aranson to find out if there really are seismic communications among elephants,’ she says.
To test the theory that elephants transmit and receive underground messages, O’Connell-Rodwell and her colleagues conducted several experiments with elephants in Africa, India and at a captive elephant facility in Texas, USA. We went to Etosha National Park in Namibia and recorded three acoustic calls commonly made by wild African alephants,’ she says. ‘One is a warning call, another is a greeting and the thirs is the elephant equivalent of ‘Let’s Go!’
The researchers wanted- to find out if elephants would respond to recordings played through the ground; so they installed seismic transmitters at a tourist facility in Zimbabwe where eight trained, young elephants were housed. The idea was to convert audible 'Greetings!', 'Warning!" and "Let's go!" calls into underground seismic waves that an elephant could feel but not hear directly through the air. 'We used a mix of elephant calls, synthesized low-frequency tones, rock music and silence for comparison," says O'Connell-Rodwell. "When the Warning calls were played, one female got so agitated that she bent down and bit the ground,' she notes. 'That's very unusual behaviour for an elephant, but it has been observed in the wild under conditions of extreme agitation. The young female had the same agitated response each time the experiment was repeated.
Researchers also played recorded calls to seven captive males. ‘The bulls reacted too, but their response was much more subtle,’ notes O'Con nell-Rodwell. ‘We think they’re sensing these underground vibrations through their feet,’ she adds. ‘Seismic waves could travel from their toe nails to the ear via bone conduction.’
For questions 30 - 33, fill in the missing information in the numbered spaces. Write no more than ONE WORD and /or A NUMBER for each question.
According to newly published findings, by stomping their feet, elephants tend to send a (30)
message to other elephants in the distance. O‘Connell-Rodwell wanted to study elephants further because he witnessed unusual (31)
of these giant animals. When warning calls were played in the experiment, an elephant bit the ground, which case was (32)
before, but when they had agitated extremely. The scientists hypothesized that elephants use their (33)
to detect the vibrations.
