Red Fox in Back Yard

Even though we're about a mile and a half from the city limits of Philadelphia, we've seen several red fox in the back yard and around the neighborhood. Yesterday morning, I saw this fox in a neighbor's back yard. The neighbor had trapped a grey squirrel in a 'have-a-heart' cage (I have no idea why he did that), and the fox was trying to get it. At first, I thought it was two fox cubs playing together, then I thought it was one fox with prey, and finally we realized that the squirrel was in a cage.

I grabbed a camera, and was able to get this picture:
The fox is looking directly at the camera..... I'll try to get a better shot next time. I suspect there's a den somewhere in the neighborhood. This looked like a mature male. He is definitely big with a massively bushy tail (which doesn't show in the photo).