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Animals' senses may have helped them survive

Before the devastating wall of water hit a beachfront in Thailand last month, elephants carrying tourists ran for a nearby hill, saving their passengers, according to news reports. At Yala National Park in Sri Lanka, dozens of men, women and children were killed as the lodge was literally flattened, but virtually all the elephants, buffalo and deer survived. In a wildlife sanctuary in Tamil Nadu, India, antelope reportedly were seen racing from the coast to the forests 10 minutes before the tsunami hit.

It's too early to know whether these incidents are isolated anecdotes or whether animals were better able to survive the disaster than people.

But many animals can hear ultralow frequencies and have a keener awareness of the Earth's vibrations. This probably didn't give animals a "sixth sense" to know that the tsunami was coming. Instead, they may been able to better detect the earthquake that preceded it, said Jan Randall, an animal behaviorist at San Francisco State University. Most people didn't feel the earthquake or suspect the tsunami was coming until they saw the giant waves. For humans, "vision is the first line of communication, then probably sound," Randall said.

Whether animals' sensory abilities helped them to survive may become clearer after the completion of several ongoing assessments.

A team from Humane Society International this week has seen animals, like dogs, cats and cattle returning to coastal areas of Banda Aceh, Indonesia, after being noticeably absent since the tsunami.

"The team has no idea where they have been. It's a mystery," said Kelly O'Meara, program manager for the Humane Society. "The animals are in bad shape because they haven't eaten or drunk properly for a few weeks. . . . The situation is very chaotic. No one knows how many animals perished and how many survived."

Jan Vertefeuille, a spokeswoman for the World Wildlife Fund, said that two of the elephants in the Yala park have satellite GPS collars; as soon as it can, her organization plans to retrieve the satellite data and confirm whether the elephants fled to higher ground, and when.

Intensely powerful events, like earthquakes, avalanches, volcanic eruptions -- and maybe tsunamis -- produce so-called infrasound or infrasonic sound waves that humans can't hear, but elephants, giraffes, rhinos, hippos, and even pigeons can. It's thought that pigeons use infrasonic sound for navigation, finding their way over water by locking onto beacons of infrasound. Some predators, according to Alfred J. Bedard Jr. of the National Oceanic and Atmospheric Administration, may have evolved infrasound detectors to hear the panicked thump of their prey's heart.

The sound of distant thunder is about as close to infrasound as people can hear, said Bedard. Below this lies a threshold where sound passes from hearing to feeling in humans.

Mammals sense ground vibrations through special detectors in their joints and feet called pacinian corpuscles. Humans have these receptors. But, although we can theoretically detect these signals, we are not conscious of them.

"Humans standing on two feet have much less contact with the ground than an animal with four feet," Randall said. "There are stories about native Americans placing their heads on the ground or tracks to listen for approaching horses or trains, and the use of drums to communicate in native cultures, so low-frequency sounds have been used at times as a secondary means of communication."

Could humans be trained to tune in to these signals more? "I am sure it would be possible," said Peggy Hill, a biologist at the University of Tulsa. "I guess that people who operate without vision, or possibly hearing, do have a heightened awareness of vibration signals."

Hill said it's possible that the indigenous people living on the small, low-lying Andaman and Nicobar islands off India were able to read the Earth's signals -- in a way that the more modern people missed -- and save themselves from the waves.

According to the Associated Press, members of the ancient Jarawa tribe emerged from the forest Thursday and announced that all 250 of their tribespeople had survived. "We are all safe after the earthquake," a man named Ashu said in broken Hindi through an interpreter.

Their survival, Hill stated in an e-mail, "just reinforces my view that we have the capacity to detect these things, but we 'override' the alarm signal as less important than ones coming in from other channels . . . and we depend more on television and the Internet for 'alerts' than we do on our own sensory abilities.

"Loss of this sort of information may be one of the costs we are willing to pay for living in modern times."

Animals could potentially be used as a low-technology warning system to alert humans when they perceive something we don't. The Chinese have developed a nationwide network to observe animal behavior in the event of a natural disaster, Bedard said. In northeastern China in 1975, unusual animal behavior convinced people to stay outside and therefore survive an earthquake that flattened their homes.

But it remains unclear whether it would be practical or useful to set up similar networks elsewhere.

"These events are so infrequent that it would be difficult to make reliable predictions about animal behavior that might warn us of such a disaster," Randall said.

"Besides, do you really think humans would pay attention?" 

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