My curiosity caught, I told him to "leave it" and hurried over to see what his excitement was all about. At first what I saw looked like a very long common garter snake, knotted up oddly. As I looked a little more carefully, I realized that it was a cluster of garter snakes, probably just emerging from their winter den.
They were relatively cold, so they stayed quite still as long as I stayed several feet away. Looking carefully, I counted at least 7 of them, of varying sizes, and all within about a square yard. In the photo to the left, there are actually 2 garter snakes. The one on the left is pretty obvious, but if you look closely, you can see the body of another one behind him. Follow that body to the right, and you can make out the second head, partially hidden behind an out-of-focus, dead plant stalk.
The photo to the right is yet a third garter snake from the cluster - nothing special, other than I thought the picture turned out reasonably well!
After taking all the various permutations of photos that I could think of without moving about too much (and spooking the snakes), I moved on to let them continue their lives without further upset. I haven't seen any of them since...but I still check that clump of dead stalks daily!