Researchers discover how a tiger’s roar can paralyse its prey

By Andrew Morgan, in London
A tiger’s roar is so intimidating that it has the power to paralyse animals and humans within earshot – a phenomenon that has, until now, baffled researchers.
Scientists at the Fauna Communication Research Institute in North Carolina have discovered that the tiger’s secret is its ability to make very low-frequency sounds that any prey will feel, in addition to the threatening rumble that is usually the last thing a victim hears.
Researchers have been working in the field of bio-acoustics, studying the frequency, pitch, loudness and duration of animal sounds in order to understand animal behaviour. They have established that the tiger emits low-pitched “infrasound”, a growl so deep that it is inaudible to humans. All big cats have this skill, although to a lesser extent than the tiger.
Humans can only hear frequencies from 20 hertz (cycles per second) to 20,000 hertz, but tigers, whales, elephants and rhinos can all produce sounds below 20 hertz. The tiger mixes infra sound growls at 18 hertz and below with the roar that we can hear, and the result, according to Dr Elizabeth von Muggenthaler, president of the institute, is that humans can feel the tiger roar – a sensation that causes momentary paralysis.
That blast of infrasound means a tiger has the capacity to paralyse even trainers who have worked with them for years.
“It rattles and shakes people, and it’s stunning because it happens so fast, just a split second,” Dr von Muggenthaler said.
“It’s an incredible force coming at you. When they roar, tigers often move at great speed from lying down to straight up. During that time you never have any thoughts of running away because you’re so glued to the moment in time.”
Tigers do not only use infrasound literally to scare their prey stiff. It is an invaluable means of communication for them because it can travel long distances.
The research will not surprise military scientists, long aware of the potential of infrasound as a weapon. Several devices that can stun advancing troops with a shockwave of low-frequency sound are being developed.
The scientists say tigers are “remarkably articulate” animals which, in addition to roaring, have a wide variety of special sounds for use with other tigers, such as chuffing – a type of affectionate greeting – growling, hissing, grunting and mewling.
In the first study of its kind, Dr von Muggenthaler and her colleagues recorded every growl, hiss, chuff and roar of 24 tigers at the Carnivore Preservation Trust, in Pittsboro, North Carolina, and at the Riverbanks Zoological Park in Columbia, South Carolina.
Last month she told a meeting of the Acoustical Society of America how tigers “talk” with a range of messages. It is the use of infrasound, however, that really singles them out.
The Telegraph, London
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