Nope not one chew mark so far. I was also bit concerned about the holes I melted in the sides but the room they are in doesn't get a good cross draft so I felt I needed the extra ventilation they provided.
I'm not sure why they don't attempt to chew out. The tubs are very smooth in their interior...that probably helps. I do provide a lot of chew stuff daily as far as bones from our dinner, carrots, etc. so maybe that helps. Their feed mix is varied so they have stimulation picking through it. I don't overstuff the tubs with rats so perhaps that's a factor? The younger busier rats (feeders) get toilet paper tubs and stuff like that to knaw on. I prefer these clear tubs as I feel that may also help as they can see out and maybe don't feel the need to chew out to see what's up around them (rat's being highly inquisitive critters).
So far they seem very content in these tubs. Well other than my female with the almost weaned big litter who is madly trying to jump out whenever I open the tub to feed! She's about had it with the whole "jump on mom" aspect of mothering a large active litter LOL
Oh one thing about those tubs though. The locksnap lid is pretty good but I found a slight give on the corners so added extra security there on the lid just in case.
~~Jo~~