I understand it to also be known as the Asian Black Rat, Roof Rat or Ship Rat. It apparently carried plague fleas that spread the Black Death. www. ratbehavior.org, in their Rat Systematics column, has photos under "Quiz, Norway rat or Roof rat" that illustrates the differences.
i've also read that rattus rattus doesn't breed as quickly as rattus norvegicus, and that they are much more susceptible to cold temperatues. so rattus norvegicus probably out-competed rattus rattus since they are vying for the same niche.
"The black rat, (Rattus rattus) sometimes known as the ship or roof rat, is best known for the part it played in spreading the plague or black death during the Middle Ages. The black rat is now quite rare in Europe and in some countries is an endangered species."
smaller rat that is found more commonly in tropical regions
I did a bit more reading & some sites suggest they are not as social & can be somewhat aggressive... both traits that make it difficult to domesticate
I'm not sure if it is Rattus rattus is the same type of rat I recall reading someone refer to as her "wild things" or "wild furkids". I don't even recall what board I recall reading about them. At any rate, the wild babies she raised would allow her to handle them but not really into anyone else but of course, she was Mom, she feed them when they had no Mom ma rat to nurse from. As much s she loved them I guess it is safe to say that they were somewhat shy & not as social as the domestic rats from the Rattus Norvegicus lines. I also recall the mention that they were much smaller in size.
If I can recall where I read about them I will link to it.