It's not quite five in the morning and we're walking along a track in the forest. The moon is high in the sky and provides enough light for us to see where we are going. A wolf howls in the distance. We have come to Poland's Białowieża Forest, the last refuge of the European bison, in the hope of getting a glimpse of this greatly endangered animal in its natural habitat.
But the bison is not quite so keen to be spotted, so we must be stealthy in our approach. We turn off the initial track, and Mateusz Szymura, a park ranger and our guide to Białowieża Forest, signals to us to keep quiet. We've already switched off our mobile phones and have been warned not to use our personal cameras. Any sound will startle the bison and our journey will be wasted.
When we enter a clearing, Mateusz realises that the viewing platform we were going to use has been dismantled. So he takes us into the trees on the edge of the clearing, where we sit and wait for dawn to come and for the bison to appear. Our long nighttime wait is interrupted only by the roar of a stag from somewhere deep in the forest.