I've only been collecting rosys for a couple of months, since I moved to La Mesa, Just East of San Diego. Let me know if what I found is common, but it seemed fantastic to me.
I wanted to check out a new part of the California desert East of San Diego. I looked at the weather report for that area and realize that for the foreseeable future it was going to be something like: “high: 82, low: 43”. I reasoned that rosys might like to get under warm rocks in the late afternoon, and that if I rolled over rocks then, I could find some. I got out there later than I wanted to, about 5:45, and spent an hour rolling over rocks. I spooked one alligator lizard, but saw no snakes. I was working the arroyos (dry creek beds) and decided to cross a flat “mesa” to get from one arroyo to another. There weren’t many rocks on the mesa (“plateau?”), just short brown grass, sand/dirt, small rocks, and the occasional little bush. I was scanning the ground out of habit, mostly to avoid stepping on a rattlesnake, when I saw what had to be a rosy laying on the ground, in the open, about fifteen feet to the side of my line of travel. As I walked toward it I confirmed that the color, pattern, and girth definitely said “rosy”, but the snake was way to long. It looked to be at least five feet long, which definitely said “not a rosy”. I stopped a few feet away to make a positive ID before I touched anything. It was not a rosy. It was two rosys! They were each big and thick, and they were stretched out nose to nose. They didn’t move and it soon became clear what they were doing. Their noses were about two inches apart, and that two inches was occupied by the mouth of a rodent hole. They were each poised, on opposite sides of the hole, waiting for a rodent to come out. Their necks were raised a little and curved a little, ready to strike, and they were focused on that hole.
They were both female, big, and fat. They had a light silver/grey background with chocolate brown, irregular stripes, and a light colored belly with black speckles. I felt amazingly lucky, not just to find them, but to observe their hunting behavior. I decided to scan the rest of that flat grassy area, reasoning that if conditions were correct for these two, there could be more in the area at that time. I’m doing this mainly to learn the animal’s habits, and I wanted to know If I had discovered the proper conditions, or just found something that defied normal behavior and was just luck. Twelve minutes later, about ninety feet from where I found the first two, I found another one. This one was a little smaller, male, and partly under a small bush. Its markings and color were identical to the other two. This was getting ridiculous. I wondered if I could make it the quarter mile back to the truck without finding any more. I made it.
I guess that, this time of year, the prime hunting time is an hour or so on either side of dusk, before it gets cold. That must be when the mice come out. My theory is that it gets cold quickly after dusk (down to the low 40's) so they don’t have all night to hunt. The day, while not so hot they can’t come out, is both more dangerous, and I suspect, the rodents are much less active during the day, even if it only gets up to 82. So the rosys have a rather narrow window in which to hunt, maybe just a couple of hours (one hour before and after sunset). There’s probably a lot of exposure during that window.
Thanks for letting me share the experience.
Ed