PICS: Elephant grumble tells his age

"That elephants produce these incredibly low frequency sounds which travel across many kilometres is amazing enough. But what's even more amazing is that these sounds can be used to assess not just the number, but the ages, of elephants over large distances. That's a powerful tool for conservation, and one that's less invasive and more cost effective than other methods, such as radiotagging," said Andrew Horn, American Editor of Bioacoustics, Dalhousie University, Canada.