How to distinguish between rat and mouse in Chinese?
Actually, in ordinary life, Chinese don't distinguish mice and rats(Frankly speaking, when I was a student, studying English and met the two words, I was also wondering why there are two words in English?). We just call that dirty animal that often appears in the houses "老鼠" or "耗子"(oral word,common in dialects).When we see a mouse(rat?) in a field, we may call it "田鼠"(田 means the field). 

仓鼠 is a kind of pet(one of my friends raise two). Wiki tells me rat is "大家鼠" and "mouse" is “小鼠", but I and people around me don't care this.

Of course, in scientific circle, academical researchers will adopt the Binomial Nomenclature(in Chinese, 二名法) system to distinguish them.