What Causes a Whistled Language to Emerge?

There are something like 80 is that have been reported. Somewhere around forty of them are very well documented. Almost all of the whistled languages occur in two different types of environments, either in mountainous terrains or rugged mountains. Whistling also allows human dialogue to go undetected by animals,. Since many animal species also use whistling. Other advantages are that whistles are easy to locate and difficult for strangers to recognize.