As far as I can tell this is part of the "excitement" phase of death or
euth.  The body reacts to the euth solution or the final stages of death in
different ways.  Most animals and humans too releive themselves at time of
death also.
 
i have seen the bottle brush tail a few times, but with pre sedation you
can bypass alot of pre death anxity and pain.
 
i think there is some pain involved with death by euth, so as we know
bottle brush is associated with excitement which sounds weird but many
ferrets try to fight death and that causes bottle brush tail.
 
This is just my opnion, and a s a vet tech in the past and sitting in on
way to many deaths.
 
Maybe Dr. williams can elaborate more on the subject.
Cj
24 Carat Ferret Rescue And Shelter
[Posted in FML issue 3304]