Subject: Estimating Fox abundance through scat analysis

Can someone tell me how scientists are able to get an idea of how many foxes 
are in an area simply by looking at the amount of fox excrement around?   If 
there is a reasonably simple formula, I would like to know what it is.   There 
is a considerable amount of red fox dung at one of the local woodland areas, 
and I would be interested to find out how many foxes are likely to be about 
were I to count the number of scat piles I encounter whilst walking my dog.   
Many thanks for your time.

Re: Estimating Fox abundance through scat analysis