The smell of a decomposing mouse somewhere forward of the firewall

That dead mouse is, as someone else pointed out, probably
inside the heat muff against the muffler, along with his nest, and the
next time you go flying the nest materials could catch fire and make
life too interesting. At least it would finish off the dead-mouse odor.
I used to use mothballs, until successive generations of the
little beasts got used to the smell and made their home inside my
airplane anyway. Now I use the poisonous bar bait, which works well but
might also be killing the airport cat, who helps control the mouse
population and could catch and eat poisoned mice before they're dead.
Oh well, there's never any shortage of stray cats.
I once watched a cat chase a mouse, corner it, and the
terrified rodent jumped well over two feet into the air over the cat to
escape it. They don't have to climb when they can jump like that. They
jump into our garbage cans here in the shop, those big backyard cans
which are about two feet high, and if there's not a lot of loose stuff
in the can they jump out again after filling up on scraps.
Someone needs to invent an electrocution-type trap for hangars.
I had ideas for an air-powered cannon that might have a breech trap
that would close after the mouse entered it, and an
electronically-controlled valve would shoot compressed air from our
shop compressor and blast him through the barrel (which would be
permanently installed in the shop wall) out into orbit. The airport cat
would have his house inside the landing zone.

Dan