And unlike tiger rattlesnakes and black-tailed rattlesnakes (another common species around Tucson), both of which tend to den by themselves, Western diamondbacks often den in groups of up to 10 to 20 individuals in the same area. They may hibernate inside a pack rat den or along with other reptiles, such as Gila monsters and desert tortoises. The Western diamondback typically dens on rocky slopes or in small caves that form on the sides of washes. Tiger rattlesnake dens are in rocky outcrops, so they go into the cracks and crevices of rocks-about 2 to 4 feet down-and you don’t see them again until spring. Where and how snakes den also varies by species. Western diamondback rattlesnakes, a larger, more common species, will go into their dens a little later, on average. One species that I have studied extensively is the tiger rattlesnake, which is a smaller, retiring species that tends to go into their dens from late October to early December.

That said, the timing and length of the overwintering period varies by species. Sleep in snakes is especially complicated because they don’t have eyelids, so we can’t even tell if they may be sleeping based on their eyes being closed.

They certainly shut down their systems and conserve energy due to cold temperatures associated with hibernation, but they don’t appear to sleep in the classic mammalian sense, with characteristic brainwave patterns associated with different levels of sleep. We are not sure that snakes really sleep-at least not in the way that humans sleep where they might as well be dead from a self-defense point of view. There’s some debate on whether we should call it “hibernation” or “ brumation,” which is essentially hibernation in ectotherms, but for our purposes it’s okay to call it hibernation, or a period of winter inactivity. For the most part, around Tucson, at this elevation and with the winters we have, almost all reptiles undergo a hibernation period. They will stop feeding and enter into a sometimes long (several months) period of inactivity. Because their physiology is temperature-dependent, this allows them to slow down all their systems and conserve energy. When winter temperatures get too cold, snakes typically go underground or into natural shelters, like rockpiles or mammal burrows, to avoid freezing. Therefore, snake body temperatures are coupled with environmental temperatures, although they are very good at behaviorally thermoregulating to keep their body temperatures fairly constant. Snakes are ectotherms, which means their internal body temperatures do not remain constant like mammals, which are endotherms. Do rattlesnakes in Tucson hibernate during the winter? He is an investigator in the university’s world-renowned VIPER Institute, serves as associate editor of the Journal of Wildlife Management and is especially interested in how urbanization and conservation efforts affect snakes.

Goode has published over 40 peer-reviewed journal articles and book chapters related to ecology and conservation of herpetofauna, particularly snakes. They’re shutting down their systems, conserving energy and revving up for reproduction, says Matt Goode, assistant research scientist in the University of Arizona’s School of Natural Resources and the Environment. When snakes hibernate during the cold-weather season, they are far from inactive, at least metabolically speaking. On warmer winter days, you may see a rattlesnake, like this black-tailed one, outside but close to its den.

Do snakes hibernate in winter