I don't trust my dogs with my rats. We have 6 dogs: 5 boxers and then a shepherd lab mix. My shepherd autumn isn't too interested in the rats but when confronted with them she just licks them. for the most part, the boxers are either afraid of them or they lick them but our youngest puppy who is about a year old, when introduced to one of our girls, tried to bite her head in an instant without any thought. Luckily she didn't but since then she's so fixated on the rats that she'll sit and stare at the cage for 15 -20 min at a time. bad puppy!
now that i've heard this though i'll never leave them in my room alone with the rats. I never thought a dog would actually break into the cage to try and get them. That's so horrible!