If my ferrets could crew through chicken wire I wouldnt be surprised if they also donned big red capes and flew around saving the world every night after I'd gone to bed. 
  
BS mate 
 
  
I lost my first ferret after he chewed through the chicken wire on his box, too. Belting little silver hob he was, tame as a puppy.  So it seems you're in the minority there mate. Galvanised weldmesh was the only thing I'd use from then on. 
 
  
100% chicken wire is shit mines ate through even doubled up now they,re workin it s a lot quieter in the garden