When I first started focusing on wildlife photography, I had to really work at focusing my images to just one subject. I had a bad habit of wanting to show everything in the scene. But when you show everything in a scene the viewer's eye isn't sure what to look at and will lose interest in the photo. So I really practiced on narrowing down and composing my images to the most important subject. 

One way to do this is to keep a clean background. For wildlife photos, using a wide open aperture will help bring the focal point to your subject. Wide open apertures (f4, f4.5, etc.) will blur and soften the background, thus helping the eye focus on the subject in the foreground.

Another way to keep a clean background is to avoid clutter behind your subject. This might include thick trees, distracting colors or other animals. If possible, move and recompose your photo to clean up the background.