Like the Thornscrub Hook-nosed Snake, this species is widespread in Mexico (and further south) but just barely present in southern Arizona. As you might imagine, they are difficult to notice even though they aren't necessarily rare in their habitat.

This one was venturing out onto the road, head and neck held high ("periscoping"), when Matt Cage, Andrew DuBois, and I all spotted it at about the same time as we drove past. Matt slammed on the brakes, and we all jumped out and ran back to try to locate it. It had turned tail and disappeared into the roadside vegetation. We searched for five or ten minutes to no avail, and were on the verge of giving up when another carful of our herping buddies pulled up. They got out to join the search, and within about thirty seconds eagle-eyed Gerrit Jan Verspui spotted it up in a twiggy bush.

We captured the snake and brought it back to our lodging for photos the next day (and then released it back where it was caught).