Many years ago in Colorado I believe there was a wolf population (might be red wolves from Mexico) but nothing at the time was substantiated. I believe bears and lions do account for elk calf mortality but they have always been there and there should be no biological reason why that form of predation would suddenly rise. When there is a dramatic drop in native wildlife generally there has to be either a man made problem or disease. Here in Northern Vermont our moose herd has taken a dramatic drop and the state biologists have cut down the hunting permits allocated and done some studies to determine why the numbers dropped. They came up with winter ticks which are now epidemic proportions on the calves which cause them to rub against trees to try and get them off. This action removes the hair and many freeze to death due in part to less hair and also from blood loss from thousands of ticks which are on the calves. They blame it on warming climate which allows the ticks to survive further north than before. I am a Vermont native and live within 30 miles from where I was born. I am 70 years old and can't remember ever even hearing about ticks in Vermont. We now have them in numbers great enough to cause lime disease to be of epidemic proportions. Something changed.