Estrus Buzz

[WapitiTalk1]

This elk sound goes by various names but the estrus buzz is the one I hear most often. What does this sound mean when heard in the elk woods? Does it mean a cow is coming into estrus? When should a caller use this while in the heat of elk battle to increase the realism of their calling set? Below is a very good clip of this sound.

[sasquatch]

Im as green as they come but it seems as if she is being demanding or desperate so to speak, as if she is disconnected from the heard or something and trying to find company.