I hunt in Idaho and live next to my hunting areas, so, I've learned them very well. I've noticed less and less bugling over the years but stay out all night in some spots and regardless of whether there is a moon or not, they bugle all night long. Early season is typically uneventful due to heat and lack of activity on the elks part. What I have noticed is that hunters are bugling more and more. This year I spent 2 days the previous week in the location of my opening morning hunt. Elk everywhere but no bugling. So opening day comes. I listen to a person come up the bottom and bugle every 5-10 minutes. What a goon. Not one elk answers back all morning. Something similar happened to me last year. I don't understand where hunters are learning to hunt elk you need to call constantly. I've learned that early season and in areas with OTCs being quiet is typically more effective. That morning I had a spike and cows under 20 yds alnd the fool in the bottom bugling.
Interesting many folks blame the lack of bugling on wolves but I hunt in areas with and without and I'd venture to say the human component is a major reason why the elk don't talk much or do it at night.