Yellowstone is the only place in the United States where bison have lived continuously since prehistoric times. By 1902, poachers had reduced Yellowstone’s herd to about two dozen animals but the recent estimates suggest this has grown to around 5,000-5,400. It is America's largest and oldest wild, free-roaming herd.

We only film bison in Yellowstone in the depths of winter. There are two reasons for this: one of course is that the traffic is bearable in the winter and we are very often on our own and out of the park by 10 am; the second more important factor is that the presence of snow plays to the animal’s fortitude. I would not film the Amalfi coast in the winter, as it is a summer holiday destination, and in the same way I have no interest in filming in Yellowstone in July.

I tend to focus on the male bison which can weigh up to 2,000 pounds and stand 6 feet tall. From the right angle, their enormous heads and curved horns elicit imagery of mythological beasts; they are part cow and part fantasy. The bison are a revered part of the tapestry of Americana.

This immersive photograph was shot on a remote camera with a wide-angle lens on the road between West Yellowstone and Madison Junction. It’s an iterative process and I often fail simply because I am not in charge of the bison’s movement. But a pattern can develop and then we must be patient.

Yellowstone is very accessible these days and there are many photographers up there every day. I think the important thing is to be true to oneself and do what you do.