I'll look that up Mike, thanks. There isn't a lot of research on artificial hibernacula - what works, where and why. When we moved to our farm we found and old well. About 15 feet down was the water level, no way to know how deep the water was. But the thought of my son falling into it motivated me to fill it up with broken chunks of concrete I found elsewhere on the farm. I tried to choose pieces that created holes large enough for big fox snakes, but not so large that small snakes couldn't crawl up. Anyway, not very scientific, but the following spring I watched 8-10 snakes emerging from it, all male garters. They hung around the rocks coursing back and forth looking for females. If I got down close and wiggled my fingers they would stream over close and carefully smell my hand.

So anyway, we built this larger hibernacula with a backhoe. Its 7ft deep and maybe 10 feet wide with a sloping bottom. Its filled with broken brick, covered with heavy rubber and earth. Facing south by south west. We'll see...

Joe
Boone Iowa