think so, there are plenty of rabbit muck around and with the first one I tried today a rabbit bolted almost straight away but the ferrets seemed completely oblivious to it. 
 
Muck outside isn't always a sure sign of it being occupied,are you using a dog for marking or just trying holes? 
 
Don't have a working dog yet, I'm just using nets.  At some point next year I'm going to get a lurcher but at the moment it wouldn't make much difference as they rarely bolt anything anyway.