You're going to laugh ... but I was told that the insulation once was (but no longer is) made using soybean byproducts .... which served as a rat magnet. Supposedly the new stuff is not nearly as tempting a dish.
(And I won't quibble over whether that's a rat, mouse, or vole in the picture!)
What's needed is a 'Critter Abatement Technician,' or, perhaps, a 'FEline Replacement Rodent Eliminating Technician.' Good luck.
Some years back I had a paging system that a number of speakers stopped working. Upon inspection, the rats had eaten the green wire from the 70v transformer to the volume control, JUST the green, where I used red or blue, they passed. Same wire, just different colors. Also squirrels will eat the lead roof jacks. Strange.
Oddly enough, Rodents of all types and forms have a need to gnaw on anything they can find, it keeps their front teeth in check. This is why you might find the hardest of things around have been chewed on where there are rats, squirrels, etc. I remember an old guy from Canada telling me this some years ago. He said if a rodent isn't able to gnaw on something to wear it's teeth down, it can actually die from mal-nutrition from not being able to eat properly.
Let's face it, these days if you're not young, you're old - Red Green
I think they are attracted to the warmth of a loaded cable, can or transformer. I see lots of tunnels near the sub feeds and have found dead ones curled up by the doorbell transformer (not before putting my hand down on it first...eeeeeeoowwwwweee....poor little guy. The tooth growth thing explains the chewing.
We used to have mice as pets; in addition to the typical food, you would provide them with "chew sticks" to work their teeth on. From what I remember (this was a few years ago) their teeth grow pretty much constantly, and if they aren't worn back down they can become impacted and cause all kinds of nasty problems, including them receding into the skull.