Just got a rat yesterday, and I have a question about his behaviour. He seems fairly tame, he seems very interested in my hands whenever I put them in the cage. But, besides just sniffing, he 'nibbles' on my fingers - like he's testing to see how springy my skin is! It's not at all painful, but it's exactly the same as a bite, just not nearly as hard.
So, is this a forerunner to getting bitten? Or is he just checking to see if I'm edible?

Any ideas?
<img width="452" height="402" src="http://image.photoloft.com/opx-bin/OpxFIDISA.dll?s=cano&src=/PhotoLoft/Asset20/2002/12/22/10232/10232021_0_2093.fpx,0,0,1,1,452,402,FFFFFF">
Also, does anyone know what color he is (I'm sure there's a name for it besides grayish)?
Dawn