Silent Thunder The hidden voice of Elephants Katy Payne

What is the explanation behind the sensitive awareness showed by elephants within their own particular tribes? Katy Payne tells how a group of elephants she was observing appeared restless. They looked around them, as if searching for someone missing. Then, after a while, from over the horizon, an elephant lumbered into view. Once he arrived, the whole group calmed down, and then, amicably set off for a waterhole together. Payne discovered, through the use of high-frequency recorders, that elephants emit sounds that humans cannot hear. By her account, at least 50 sq/km can be filled by an elephant call. She also discovered that an elephant's delicate perception can detect calls with different meanings. 

1998. Softcover, 288 pages. Good condition. School award sticker in front.