Yes, they can climb upside down on wire mesh.  At least my albino Maya
the Moose could.
 
I used to keep a few hedgehogs in a baby's plastic wading pool.  It was
a good size for them, and they couldn't climb out.  The trouble was, our
evil cat Spooky, who would eat anything.  (He once growled meaningfully
at me over a slice of cucumber from a salad I was making, I thought he
was going to perforate me.  I yelled "Take it, you freak!"  He did.)
Spooky was an amazing individual, a rail thin black cat that my sister in
law didn't really want, and foisted off on everybody.  We had our turn.
She must have starved him at some point in his history, because he was
just insane about food.  His specialty was catching and eating one of the
enormous rats that lived in our barn.  They lived on spilled grain for
the potbellied pigs and were HUGE.  Each one probably weighed about a
third what Spooky did.  It took him a long time to eat one, and once he
was done he would lie on his side in the grass going "oh god, oh god, I'm
gonna pop..."  You could actually *see* the rat bulge in his belly.  He
was that thin, and it was that big.
 
Anyway, Spooky would jump into the pool to steal the hedgehogs food,
while they huffed and puffed and vibrated in impotent rage at this
violation.  They do that.  When they are upset they make a sound like a
rattlesnake having a nervous breakdown.  Spooky didn't care.  There was
food.  Sure, it was formulated for hedgehogs.  It was *food*, wasn't it?
Yes it was, and pricey, too.  We had to stop these raids.  We took sheets
of chicken wire, lay them down on the floor next to one another, and
"wove" the little broken ends together.  It was tedious, and we got our
fingers poked, but then we had a sheet that we were able to use to make a
dome over the top of the wading pool.  It didn't bother the hedgehogs,
and it kept Spooky out.
 
But Spooky was a mere cat, and not a ferret.  Maya was a FERRET.  And
NOTHING keeps ferrets out.  She slithered in at the spot where the
chicken wire was its loosest, where we opened the dome up to feed and
water the hedgehogs inside.  NOTHING keeps Ferrets out, but sometimes,
things do keep ferrets IN.  Imagine my surprise one morning when I came
down into the kitchen, and there was Maya, clinging upside down to the
chicken wire dome, scrambling around, looking very miserable.  She was
free roam ,she might well have spent hours trapped in there.  I think
when she tried to climb out of the little hole she opened up, she got
poked by the short bristly ends of the edge of the chicken wire sheet.
It was painful, and she was trapped.
 
Yup.  They can climb upside down.  I know, because Maya got herself into
this predicament *several* times.
 
Alexandra in MA
[Posted in FML issue 4885]