The secret language of elephants

Researchers form the San Diego Zoo have studied elephant language. It is well-known that elephants trumpet. Less well-known are the low growls that they use to communicate amongst each other.
Two-thirds of these growls are so low that they cannot be heard by humans. They can be detected however by special microphones combined with a GPS system. This way eight female elephants could be followed and sounds could be linked to particular activities.
The researchers were able to obtain a good picture of the hierarchy within the herd and the interactions between herd members.
The data are still being examined in detail, but one preliminary conclusion has reached the news already. During the last twelve days of gestation the growls change. The change occurs mainly in the low frequent, inaudible part of the growl. The researchers think that the pregnant elephants signal to the rest of the herd that their babies are imminent. Possibly the mothers-to-be also ask the herd to look out for predators. At an elephant birth the herd stands around the mother and her baby in a protective circle. An elephant baby weighs 100-150 kilos, but it is still very vulnerable to predators such as a group of hyenas.