I couldn't reply earlier Lou as I had to go to my 'other' job! I only get half an hour to do the banking before I vanish!
But to be honest, the first thing that came to mind was male scenting - I have some males with incredibly active scent glands, and the sugs in those cages do seem to be a browner colour.
13 is an unlucky number Lou, I think you need another one!!!
