What animal bit off metal/tin on nesting box?

[Osofluffy]

I have my 4 bantam pullets in a small coop in the yard, two of which are broody & hopefully hatching some eggs. I went to the nesting box this morning and saw what looks like tooth mark scratches and bit part of the tin/metal off. It wasn't there yesterday and all the bantams were unharmed thankfully. We do lock the nesting box at night.
I broke the nesting box into 2 photos. It just one tin/metal door.

What could this be? We are checking all the coops just to be safe & double securing.
Thank you!

 

[mowin]

How far apart are those marks, looks 3-4"? Large dog or bear possibly.

 

[Ravenseye]

The small grooves in each spot make me think a small critter. I have some red squirrels that chew through the aluminum flashing that I replace on an annual basis (thinking that they won't do it again like they did last year). I'm always amazed at how powerful little teeth can be.

 

[cmom]

Here some gray squirrels have chewed through some metal.

 

[danceswithronin]

Gray squirrel is my best guess. I used to keep my feed in a big plastic storage bin near my chicken run and the squirrels chewed a hole right through it. The marks looked a lot like the ones in your photos. They're just rats with a fluffy tail basically. I still feed them though even though they're a total hassle.

 

[swampfox440]

Rats !

 

[cmom]

Put a camera up and see what shows up on the camera.