My son's pet likes to chase trains. My Kato RDC is the fastest loco I own and was still no match for the ferret. [video=youtube;hdxZXj1jktI]http://www.youtube.com/watch?v=hdxZXj1jktI&feature=youtu.be[/video]
I have a double track loop of Unitrak with trains running under my little tree that I decorate with Hallmark train ornaments. The ferret kept stealing cars off the trains and hiding them under the couch. No teeth marks that I can tell. My son and his pet are gone now so my trains are safe.
We had a ferret that liked to hide under the couch and just watch for anything that moved. If you forgot he was under there and walked by...your feet where fair game !
I had a cat that liked to lay on a mountain on my layout and watch the trains come out of the tunnel. She would wait patiently for the caboose and then swat it when it came out.