Typical-looking sidewinder for the Phoenix area, on atypical background gravel. Normally I like to at least move stuff a little further off the road before photographing it, if that’s the way it is found, but this guy curled up so nice … and good old laziness after being out for many hours. Oh well 🙂
The big boy in the background is king of this rock, seen here with one of about 6 females that he courts and mates with. I’ve seen smaller males come wandering into this area before, and it doesn’t end well for them. The last one was chased away and actually fell about 8 feet onto rocks below.
Once named a subspecies of prairie rattlesnake (Crotalus viridis nuntius), these little orange guys are now just considered a local phenotype. They’re usually referred to as “Hopi” rattlesnake as a common name, despite having no taxonomic difference with the rest of prairie rattlesnakes … confusing for sure, but an example of how common names and the associated latin can advance at different speeds.
Over the years, we’ve noted that Red Diamond Rattlesnakes at the dens we visit seem to operate on 2 distinct clocks. One being yearly, possibly based on light levels or average temperatures, and the other being conditions in the area at that time. Understanding both can indicate what kind of day we’re going to have.
During the month that we go, they seem to always emerge at the same time each year, to within 15 minutes for as long as we’ve been going to these sites. This happens no matter what the conditions are, it seems – the snakes begin to move suddenly, and seemingly all at the same time. Even on days that it feels much too cold for anything to happen, or the bright sun seems sure to have us driving back to Phoenix with empty camera cards, the magic hour proves us wrong.
The second factor are the conditions that week or day. Meaning cloud cover, any rain that’s coming or just happened, etc. This seems to dictate what the snakes do once they are out, and how long they do it. On a good day, overcast or foggy giving way to partial sun, then clouding up again to a nice and stable warm and humid feeling, the snakes will be out and moving all day long.
On bad days, clear skies and bright sun create unstable, hot conditions that will move them back into the rocks pretty quickly. In these conditions, the air temperature under rocks where they spend the night may be quite cool overnight, but the surface is too hot to be out by 11am. On days like this, there is no benefit to coming out at all. While they may move a short distance or come out then come right back in, for the most part, they will remain hidden. Regardless, the time of initial movement stays the same.
On days where everything goes “right”, the snakes may move again in the late afternoon when shadows are long, as long as the wind doesn’t get too crazy and the gamut between day and night time temperatures is not too extreme. On these days, the snakes tend to be moving larger distances, and generally doing cooler stuff. We’ve had some great moments watching large adult snakes move through the rocks, setting up ambush sites, and interacting with the environment.
Here’s an example: a red diamond rattlesnake modifying its surroundings to create a clear strike path for ambush. This has been documented in other species, and to our knowledge, this is the first time it has been seen with these guys.
In the Spring, specks in this part of the mountain maintain a pretty regular pattern of emerging in the Morning on the West side of rocks, moving to the East-facing side (either across the bajada or just moving around to the other side), hiding during the day, then wandering back as the shadows get long. Eventually, they will move out along bajada ridges to hunt near the top of minor drainages, and continue to move laterally in this way until the beginning of the foresummer, where they retreat to other areas within the mountain to eat and aestivate. This is one of the males that I spent a few days following around while working out this pattern.
Even within contiguous habitat, some speckled rattlesnakes groups may be darker than in the surrounding areas. This is one example – one of a much darker-than-usual group that lives in a relatively small section of volcanic rock, completely surrounded by iron-rich rock. A short distance from where these snakes live, they are the more typical orange/red color they are throughout the rest of that range. This is by no means the darkest seen there, either. I have seen one young one that is grey on black, and will likely darken as it ages.
These are more photos at my largest site that I visit. I limit trips here to just a few times a year to make sure I don’t impact behavior or habitat, and its always great to see regulars show up year after year.