Pronghorn Antelope are North America's fastest land mammal and can travel at speeds of up to 50 mph. We've seen many from a distance, but getting near to one was proving to be a real challenge. I'd all but given up on the idea of getting a close-up shot, that is until we took a little used, one-lane road in Yellowstone. As we turned a corner two Antelope crossed in front of us and stopped to graze nearby. Needless to say we grabbed the cameras and clicked away until they were out of site.