A Blacktailed Rattlesnake hiding out just outside its den. It took a few years to zero in on the exact spot, surveying the area in early spring and late fall and tracking where snakes were found in early egress. Eventually, there it was – with just two snakes in it to start, but the start of many more to come. The snake wasn’t disturbed, and due to the location, very likely may have never seen a human before.
A Sonoran Sidewinder from the Phoenix area, out and about late at night as they tend to do. This one is large, for a small species, and for a male. These snakes are under two feet long, with females being slightly larger as full-grown adults. There are several reasons this may be the case, one of which being that a bigger snake can produce more babies.
These rattlesnakes don’t, and may not really be able to, slither like most snakes do. They can move in a straight line rectilinear motion, undulating belly muscles to inch forward. But more typically, they throw a loop of the body forward, past its head, and then bring the rest of the body alongside it. This is the side-winding method they’re named for. It’s a good way to move through a sandy, hot environment … often with some speed. The tracks left behind are a series of unconnected lines with a “J” at the end, pointing in the direction of travel. This is different than is often expected by homeowners, who report a “sidewinder tracks” that are typically from fast-moving nonvenomous snakes, like coachwhips and whipsnakes, moving quickly through soft matrix, leaving a swishing side to side track.
And yes, there are sidewinders elsewhere in the world … but they’re not closely related to these snakes, and are not rattlesnakes. They are a great example of convergent evolution, where a similar solution evolves to meet similar problems. In this case, it turns out that side-winding is a very efficient way to move for a snake, and sandy deserts on the other side of the world are no different.
Webber, M. M., Jezkova, T., Glaudas, X., & Rodríguez-Robles, J. A. (2016). Feeding ecology of sidewinder rattlesnakes, Crotalus cerastes (Viperidae). Herpetologica, 72(4), 324–330. https://doi.org/10.1655/Herpetologica-D-15-00042
Tingle, J. L., & Sherman, B. M. (2022). Scaling and relations of morphology with locomotor kinematics in the sidewinder rattlesnake Crotalus cerastes. Journal of Experimental Biology, 225(7), jeb243817. https://doi.org/10.1242/jeb.243817
Blomsten, P., Schuett, G. W., Höggren, M., & Clark, R. W. (2016). Fifteen consecutive years of successful reproduction in a captive female sidewinder (Crotalus cerastes). Herpetological Review, 47(2), 231–234. https://www.academia.edu/download/43375448/Blomsten_et_al_Sidewinder_Reproduction_HR_2016.pdf
Rautsaw, R. M., Hofmann, E. P., et al. (2019). Intraspecific sequence and gene expression variation contribute little to venom diversity in sidewinder rattlesnakes (Crotalus cerastes). Proceedings of the Royal Society B: Biological Sciences, 286(1902), 20190810. https://doi.org/10.1098/rspb.2019.0810
Webber, M. M., Glaudas, X., & Rodríguez-Robles, J. A. (2012). Do sidewinder rattlesnakes (Crotalus cerastes, Viperidae) cease feeding during the breeding season? Copeia, 2012(1), 100–105. https://doi.org/10.1643/CE-11-056
Leavitt, D. J., & Grimsley, A. A. (2019). Density, recapture probability, biomass, productivity, and population structure of sidewinders (Crotalus cerastes) in the Sonoran Desert of Arizona. Herpetology Notes, 12, 577–584. https://www.biotaxa.org/hn/article/view/35147/44449
A Southwestern Speckled Rattlesnake resting along the top of a drainage after a night out. During the summer months, these and other rattlesnake species are primarily nocturnal, being encountered by people mostly in the hour before and after sunrise. As soon as the sun reaches the area, these snakes make a beeline for their aestivation sites to hide for the day.
The fact that rattlesnakes are often nocturnal and that they spend much of their lives avoiding excess heat is a surprise to many people. The misconception is that reptiles, ectotherms who get heat from the environment rather than produce it themselves, want it hot … the hotter the better. You’ll see this soon, in the form of comments like “it’s getting hot! It brings the rattlers out”, warnings from fire departments, and even articles in local news when temperatures stabilize in the triple digits for the year.
But thermoregulation means being the right temperature, not just as hot as possible. In fact, a body temperature sustained above around 105˚F can kill a rattlesnake. Interestingly, the upper terminal temperature seems to be similar across rattlesnake species, regardless of the environment they’re found. It’s often over 100˚F when these snakes begin their move back to their underground hiding spots, meaning they ride the line of death very closely, staying out as long as possible for the chance to find prey. If they are disturbed during this crawl for too long, or escape into the wrong hiding spot, it can quickly kill them.
We have learned this first-hand, unfortunately, from finding snakes within our study area who were first found by snake enthusiasts, likely mid-crawl. Thanks to Instagram, individual snakes that had died this way can be tied to individual events where a prolonged photo session and subsequent release of a heat-stressed snake resulted in death. To some herpers, it may seem like gatekeeping to discuss this kind of thing, but dead snakes are a lesson to those who would hear it.
During the summer, you may see us be critical of snake relocations performed by the fire department, and well-meaning individuals. This comes from the practice of releasing these snakes to improper cover, where they will be very unlikely to find survivable conditions in time. Every time you see a video of someone releasing a snake to open ground or random creosote mid-day, the relocator watches it crawl away and may be satisfied that they helped the animal … but these snakes do not survive for long.
Claunch, N. M., Lind, C. M., Lutterschmidt, D. I. (2023). Stress ecology in snakes. In Penning, D. A. (Ed.), The Stress Ecology of Reptiles. ResearchGate.
Cadena, V., Andrade, D. V., Bovo, R. P., Tattersall, G. J. (2013). Evaporative respiratory cooling augments pit organ thermal detection in rattlesnakes. Journal of Comparative Physiology A, 199(9), 883–893.
Castro, S. A., Prado, J. V., Wang, T. (2024). The relevance of vascular adjustments to hemodynamic control in the face of temperature change in Crotalus durissus. Journal of Experimental Biology, 227(15).
Laursen, W. J., Anderson, E. O., Hoffstaetter, L. J., Bagriantsev, S. N., & Gracheva, E. O. (2015). Species-specific temperature sensitivity of TRPA1. Temperature, 2(1), 142–157.
Kamees, L. K. (2022). Competing Behaviors of Thermoregulation and Ambush Foraging in the Timber Rattlesnake (Crotalus horridus horridus): A Mechanistic Assessment of Thermal Behavior (Doctoral dissertation, University of Arkansas).
Tattersall, G. J., Sinclair, B. J., Withers, P. C., Fields, P. A., Seebacher, F., Cooper, C. E., & Maloney, S. K. (2012). Coping with thermal challenges: physiological adaptations to environmental temperatures. In Comprehensive Physiology, Wiley.
LaDuc, T. J., Borrell, B. J., & Dudley, R. (2005). Respiratory cooling in rattlesnakes. Comparative Biochemistry and Physiology Part A, 141(4), 509–516.
Carnes-Mason, M. D., & Beaupre, S. J. (2025). Temperature manipulation induces ecdysis in lab-held rattlesnakes. Ichthyology & Herpetology, 113(2), 274–281.
A Banded Rock Rattlesnake from southeastern Arizona.
A young Blacktailed Rattlesnake resting on top of a boulder. During the heat of summer, deep canyons offer cooler conditions, and water trapped in pools and wet sand months after the last rain. On the hottest, driest nights, we can often predict where these snakes are by the presence of cottonwood and native bunchgrass.
An Arizona Ridgenosed Rattlesnake spotted late on a humid monsoon night in southeastern Arizona. This is the state reptile, though relatively few Arizona residents will ever see one.
A New Mexico Ridgenosed Rattlesnake (Crotalus willardi obscurus). This federally protected rattlesnake ranges into Arizona, but only a dwindling population remains.
A Western Diamondback Rattlesnake resting in partial shade. By making small adjustments to position throughout the day, a snake can precisely regulate its temperature. While they may be encountered out in full sun, this is how the majority of basking is done.
A Southwestern Speckled Rattlesnake rests in a rocky retreat, waiting for dark. Like other rattlesnake species in the Phoenix area, once temperatures stabilize in the triple digits, their activity becomes mostly nocturnal. The late afternoon is a good time to wait for a lizard or bird to make a mistake, in the meantime.
A mated pair of Banded Rock Rattlesnakes, tucked into rocks in a minor drainage in southeastern Arizona. During the late monsoon season, it’s not uncommon to find pairs or rattlesnakes like this, courting and mating in one rock pile while others are still giving birth elsewhere. The period of seasonal rain is the peak of activity for these animals, and a lot needs to be done in a relatively short period of time.
1. Mata-Silva, V. (2011). Ecology of the Rock Rattlesnake (Crotalus lepidus) in the Northern Chihuahuan Desert. University of Texas at El Paso.
2. Mata-Silva, V., DeSantis, D.L., Wagler, A.E., et al. (2018). Spatial Ecology of Rock Rattlesnakes (Crotalus lepidus) in Far West Texas. Herpetologica, 74(3), 245–255.
https://doi.org/10.1655/Herpetologica-D-17-00091.1