Thanks guys,I have only seen them in zoo's and they were black then, This one looks as though it has a longer and possibly more prehensile tail than most brown rats I have seen.
Thanks C. I'm wondering now if the ones in zoo's -Bristol here in the UK comes to mind- exhibit domesticated rather than wild black rats. Either way they are the one animal I dislike getting to close too.
in brown rats the tail is shorter than the head-body length, while in black rats it is much longer than the head-body length. It is a very obvious difference in any individual you might see.
Brown rats are also big chunky beasts whereas black rats have a slender look because they are more arboreal (brown rats being terrestrial of course). This isn't a great way of telling them apart though, unless you're already familiar with how the animals look in relation to one another, and in young animals it is a bit harder to tell this as well. It's usually fairly easy to see it in photos - not so much when the rat is scurrying across the ground.