While the subject is always very important, the background usually consumes a significant portion of the frame and that means it too is important.
One background option is to blur it away and the Canon EF 600mm f/4L IS II USM Lens is a master at that task.
Still, bull elk are very large animals and even 600mm f/4 does not completely erase the background when the entire animal is comfortably in the frame.
At long environmental portrait framing distance as seen here, the background is going to be recognizable.
Another great option is to utilize brightness to separate the subject from the background. Having a subject in direct sunlight and the background in complete shade is one of my favorite wildlife photography situations.
An evenly-patterned background often works well. In this case, the distant evergreen forest provided that option.
For this image, the combination of long focal length, wide aperture, distant background, strong brightness difference and evenly-patterned background all work together to make the bull elk stand out and look good. It was nice of this large, frost-covered bull elk to stop at the top of a small ridge, turn his head and exhale into the early morning sunlight for me.
I did not have time to get closer to this rutting bull before he went over the edge on his way to find cows. That meant I simply had to accept the framing available at the time and that was not bad at all. The entire frame was good and with the ultra-high resolution Canon EOS 5Ds R behind the lens, I had a lot of options available for cropping. I struggled to select the one to share and eventually opted to modestly crop the image to show the elk larger in the frame.
A larger version of this image is available on Flickr.