At Last! I have found the north marsh vixen’s den.
15th March 2012: This evening I visited the badger sett I suspected for so long of being used by the north marsh vixen as a den, but there were no signs of a fox there. I heard a noise to my right and went off to investigate. Fifteen metres away from the badger’s sett, was the vixen’s real den. It was obviously a fox’s den; there were remains of previous meals all around the hole: a rabbit’s head, a dead mouse and a pigeon’s head and feathers. After all my searching, the vixen’s den is only fifteen meters from the badger’s sett I had spent so much time watching for signs of a fox. At least, my instincts were reasonably accurate.
The vixen will be allowing the cubs above ground now, so there is a chance that I will get a few photographs of the cubs, shortly.