Duke loves to explore. Every chance he gets he roams the back yard in search of something.
I don't think there is one inch of the back yard that he has not checked out. If he finds even the slightest little hole he's got his nose down in it trying to discover what's inside.
I swear I did NOT photoshop his face off. This is how you frequently find him in the back yard. Now our yard doesn't have a lot of holes in it but there are a few and he knows where each one is. He inspects them thoroughly every day for signs of change in their condition.
It isn't just underground expeditions that satisfy his curiosity.
If it's in my back yard, Duke will find it. Sooner or later, he will sniff it out.