SETI's 1st 'conversation' with a humpback whale offers insight on how to talk to E.T. 

 Humpback whale "conversations" provide valuable insight on how humans may one day communicate with life beyond Earth. 

https://cdn.mos.cms.futurecdn.net/K85W6b64wQWWZpCWfRSq54.jpg

https://www.space.com/seti-whale-conversation-extraterrestrial-communication