When I was still trapping, I only stopped cause life got to busy. But me and my brother had nusiance trapping persmits, So we would keep some red and grey fox, after the season to collect urine for next trapping season. Well one thing we noticed was when we ran out of carcuses from the prior season, and put them on "Old Roy" their urine got a very strong odor to it. We determined that was not acceptible. So come late june, we started suppling them with groundhogs, to get their urine smelling. Well after a couples of years of that, we decided fox urine prices wasnt that bad after all.