What the heck is in my ceiling?

File: ceiltext.jpg (50KB, 640x480px) Image search: [Google]

50KB, 640x480px

So I sleep on the top of a bunk bed that I share with my brother. A few months ago, I started noticing this weird scratching sound coming from the ceiling. It got progressively louder from there, until I couldn't sleep because of the noise. I ended up sleeping on the couch in my living room for a couple weeks.

I then left for a week, and when I came back, the sound was gone, so I started sleeping in my bed again. However, a few weeks later (tonight), I started hearing the sound again, but different. Instead of a large amount of small scratching, it was just one source, slowly moving around my ceiling in a seemingly random pattern.

It's now a bit past 04:00, and I figured I should ask what that sound could be, and whether I should be worried about it at all.

-Thanks in advance.

Note: The image is just one I found on google, I didn't want to wake my parents up to get a camera.