One of the things I missed while we were in South Dakota was the prairie dog pups. Two years ago there were lots of prairie dog pups popping out of random burrows but unlike my visit two years ago, there were no adorable pups to entertain us this time. My preference for photographing these cute creatures is with the 600mm lens because the depth of focus is so narrow with that lens that the subject is unmistakable. Everything in front of the narrow plane of focus and everything behind it is blurred. In the first photograph below, I used the 600mm lens from a distance.
In the second photograph, I used the 300mm and shot from the car. Although I was much closer to the prairie dog, I really prefer the depth of field in the first because the subject is the only thing that is in focus and there are no distractions. In the second, even though the prairie dog is larger in the frame, everything around it, including the grasses and the dirt, seem to compete with the prairie dog.