In misc.survivalism Doug Miller wrote:

Yes, I've heard that too -- and it's clearly nonsense. Ever seen a mouse
skeleton? The skull of an adult mouse won't fit through a hole that small.

Half an inch is believable. Pencil-size is impossible.

Are their skulls rigid?

--
The whole problem with the world is that fools and fanatics are always so
certain of themselves, but wiser people so full of doubts.
-- Bertrand Russel