Our Sunshine is not exactly bright

That's what we have to think when we leave her hitched outside for several hours and come home to see this:

This, in case you can't tell, is Sunshine's bowl. When I left the house in the morning, I filled it with water. By the time I came back, she filled it with dirt. Judging by the fact that most of dirt was wet, there was still water in the bowl when she started digging. The same happened to her food bowl once or twice before.
She started doing it about a month ago, and we have no clue why.
And here is Sunshine herself: