In any case, I took about 2 1/2 minutes shooting the doe, moving a bit along the trail for different perspectives. Usually when I'm approaching, or passing by, wildlife I start shooting early on in case the critter decides to exit the situation. If it doesn't, the early shots usually get discarded in favor of later, closer shots.
In this case, I was right up on the deer when I first saw it between the trees in the first shot. All of these shots were made with a Canon EOS 50D, the EF 300mm f.4L IS USM lens at f/5.6, using spot metering and ISO 400. The shutter speeds range from 1/125 of a second to 1/250 of a second depending on the lighting.
These images are not cropped at all and, as you can see, 300mm is plenty of lens for deer on Peebles Island with a crop sensor camera. Usually, the biggest problem is getting a clear view without underbrush, leaves or branches in the way.