I know a thing or two about these guys. Here is my story of rats attack.
Around 2005, I got a message on my cell phone at night, from a monitoring server, that one of the app servers is down. I tried to login remotely without success, ping didn't go through. I dragged myself up and went to the server room. A colleague who received the same message got there at the same time. From the terminal, we saw that the server was running just fine. We checked the network cable, it was cut, and looked like it's bitten by something. Other cables were also bitten to lesser degree. Some little animal was grinding its teeth, we guessed. We replaced the cable, and went back to sleep.
The next day, I passed by a co-worker's desk, saw he had a web cam. I borrowed it, and set it up in the server room, near the machine whose cable was bitten, and wrote a cron to snap images during the night.
We received another message the second night, another server went down. We went to the server room again, sure enough, another bitten network cable. Not only the network cable, the head of my Philips cell phone charger was completely bitten off. I was working in the server room the day before, and had my cell phone charged there, and forgot to bring the charger back to my desk. I was pissed. We check the photos snapped by the web cam... ah, here it was, a small rat, the size of the fist of a small boy. I told myself I'd take care of that pest.
The third day, we checked around, and found a small hole in the elevated floor in a corner. We guessed it must come out from there. We surrounded with whatever we could find in the office, put an old IBM machine that had been replaced and was laying around, connected the web cam to that machine and set up to snap photos again. My colleague went to the grocery store to buy a mouse trap, and put it there. We hoped that the mouse trap would catch it right there.
The third night went without any incident. In the morning, we went to check again. Oh, it was awful. The rat was lying there, its hairs all messy, and we still could smell something. The power cord of the machine was half bitten. We put the photos together into a slide show, and saw that as it was biting into the cable, there was sparks coming out, and the rat was obviously electrocuted on the spot. We showed that to the colleagues in the office and had a good laugh, some of them thought it was really gross, and that we were cruel, and that we had really mistreated animals.