Southwestern Field Herpetology

Southwestern Field Herpetology
Mar
13th
2017

Red Diamond Rattlesnake Staging Behavior

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.

And this pair that we found courting …

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