Do You Know What Animal Dug This Hole in My Backyard?

As I was looking over my backyard lawn at the dead grass over my septic tank, I noticed something peculiar very near where the tank is buried. What animal did this?

Hole in the Ground

This is the hole in question, and based on what I've observed throughout the summer, I think I might know the culprit behind the dastardly digging.

My concern is that the hole is on the upper corner of the septic tank, where I can clearly see the outline of it since the grass over it has died. It makes me wonder if that could be a problem.

It also looks like whatever it is is bringing things into the hole to get it through the winter. Notice the pine cone and leaf placed at the entrance. They wouldn't have landed there on their own.

Wildlife in my Backyard

Two types of wildlife wander into my backyard. They're both looking for food, and when I haven't mowed my lawn lately, it's like a wildlife feeding zone.

The first animal always pops up in late spring or early summer. A doe and her fawn quietly wander through my yard, and some years there will even be two fawns.

The picture is a little blurry because of how far away I stayed to make sure I didn't scare them away. Obviously, neither of them can dig a hole underground, much less get into it.

I believe this is the culprit.

Groundhog Day

I took this photo through the bathroom window seconds before he took off into the woods. Groundhogs come to my backyard every year, but this is the first time I've ever come across a hole in the ground in my yard.

I assume he's planning for the winter, and it doesn't really look like he's doing any damage, so I'll let him do his thing.