Yes. I use toilet paper and paper towel rolls, old cereal boxes. or any cardboard I have laying around. They will also chew things made for dogs like whimzees, greenies, etc. and the wooden chew toys you can buy for hamsters, guinea pigs, or other rodents. Mine enjoy hiding in the old cardboard boxes as well and they make good houses that you can throw away when they get nasty.

Rats don't tend to kill litters as often as mice and usually there is a cause like not enough protein in their diet. You can supplement their diet with boiled eggs, tuna, or other protein when nursing to help them keep weight on and produce milk.