Probably a mouse. A mouse in an attic can make quite a bit of noise. The mouse itself is being reasonably quiet, but the wood ceiling joists transmit the sound downstairs very nicely. Can hear a mouse scampering along a joist, rustling sounds as it works its way into a comfy spot, and louder chewing sounds as it sharpens its teeth on a top edge of a joist. The chewing sounds are amplified by the joists, the actual amout of wood removed is tiny, but it can
sound like a lot!
Living in TX, the friendly mouse in the attic doesn't seem to exist here. Rats instead. Years ago I went to a town's park district pest seminar put on by an old-time exterminator here. He said using poisons on mice was usually OK, that if they
did die in a wall they just dry up and mummify. But a rat was a different story - stinking for a
long time! Warfarin-based baits tended to be good, as they were slow-acting, and the vermin felt ill and would head outside to wait and die. I tried that here on rats, they were getting up to soffit and then to attic via going behind some siding corners, which I later totally renovated and solved the problem.
While using the warfarin, I came home one day, and saw a rat sitting in a narrow flower bed. It was looking right at me. I thought there was
no way I could get something to club it with, that it would be long gone first. I went the long way around, and came back wearing a glove and brandishing a piece of 1/2" rebar. I moved up on it ever so slowly, always expecting it to suddenly take off. Slowly, slowly...
Then I struck! Whump! Hit that #*@#* again! Whump!
Feeling triumphant at a job well-done, I then realized... that it was already... dead. It was just sitting there in a very life-like position.
So much for the cave man hunter!
I always thought a crawl space was below your house (for houses without a basement, but not built on a slab), and just below the roof is the attic.
Yup!