Whose hole is that? Habitat study along the way

We were headed home from the play ground, when my four-year-old noticed this hole.  "Look, Mommy, a hole!"

My five-year-old immediately declared that this was an animal home.  After determining that it was a fairly deep tunnel, we began to discuss what type of animal would live in it.  He thought it was probably a muskrat.  She thought it was a beaver.

I asked whether the hole was big enough for those animals and whether they would typically want to hang out at the top of a hill.  My older child began to doubt his hypothesis.  The younger one is sure a beaver wants a tunnel from the river to the top of that hill.

I would guess that if it really is an animal burrow, it would belong to a snake, but I don't know.  It is fun to imagine possibilities.  Maybe some day one of them will be am expert naturalist who can point out the details needed to solve the mystery.