What is “the master call”? Why is it the most important signal for an elephant to learn?

The master call is a low and loud vocalization made by an elder elephant, usually the matriarch. It is the most important signal for an elephant to learn is because it is the ultimate warning to alert a herd of pending danger. The master call not only unites the herd, but allows the elephants to work as a team in an attempt to escape imminent harm or avoid potential predator or human interactions.