Many times animals will do this when they have a deprivation from weaning.
The suckling need is in all young animals0-- humans included.  When you
factor in that ferrets are not usually fully weaned until 8 weeks of age
( sometimes longer) and they arrive in a pet store at 5 1/2 weeks of age--
that is pretty clear that the ferret is still requiring to suckle, nurse
from it's mother.  This is one explanation I can offer, and feel
comfortable saying with my first ferrets did observe.  How to curb it--
well , you won't if ferrets are sold that young.
 
The only other times I have observed this is in older male ferrets who were
diagnosed as adrenal symptomatic-- go figure?
 
My personal opinions only,
 
Alicia
[Posted in FML issue 3015]