About 20 years ago when I was working at a wastewater plant, the AC went down. We had the doors to the building open. I come back one hour, only to find my sample refrigerator and DI (deionized) water dead. I check the breaker, it's good. I pull the sample frig away from the wall, and there's a muskrat looking at me all squint eyed. No idea how long he'd been in the building, but in one hour he popped himself twice with 120V and took out 2 pieces of my lab equipment. Not having access to any electrical tools at the time (nor being an electrician), I took my leatherman tool, stripped back the wiring, twisted the strands back together, and taped it up with scotch tape until morning time.
I caught him with a fishing net and took him back outside.
I've seen squirrel damaged wiring too in attics, eaves, soffits. Mice got my coffee pot and fry daddy wiring a few years ago. They love wire, even when (or perhaps especially?) when it runs a billion dollar particle accelerator:
http://www.cnn.com/2016/04/29/tech/cern-weasel-irpt/index.html
and ofc most of us have seen or heard the results of a squirrel chewing on a pole xfmr primary...
eta: they are capable of chewing thru stranded wire anyway, guess it's thin enough and their teeth sharp and hard enough to bust those little wires. Never seen one eat 14ga or bigger, just the surrounding insulation. I've heard that electromagnetic fields attract rodents, hence their like for energized wiring, but cant confirm it.
