Can you tell a mouse from a baby rat? After reading these tips, I correctly identified 12 out of 12. (And I didn’t have to count the nipples!) Can you tell the relatively civilized Black Rat (Rattus rattus) of the Pacific Islands from the marauding imperialist Norwegian Rat (Rattus norvegicus), which has conquered most of Eurasia and North America? Do you know how to launder your pet rat? It’s all at ratbehavior.org.