Why are we still catching rattlesnakes in the winter?

You may notice that our social media feeds are still full of rattlesnake captures and relocations, even in the coolest months of the year. Be assured: yes, rattlesnakes are hibernating (or brumating if you prefer) in the winter, roughly from November through February. However, as we’ve explained in previous winters, they can still be found from time to time on the surface.

The biggest reason you’ll still see so much from us is because we meter our content so that we don’t blow you away with 20+ posts during the summer days, and make you think we’ve disappeared during the winter. Every call is unique and interesting, with lessons and experiences that should be shared, so we space it out. That means that many of the photos you’re seeing in the winter may have been from calls we ran in October, etc.

There are of course snakes that are still active during the winter, both by their own choice, and not. We cover some of the reasons you may see one at your house during the cooler months in a previous post, named after the most common comment we see on photos of snakes found in the cooler months. “I thought they were hibernating!

Why would rattlesnakes be active when it’s so old outside?

One of the biggest misconceptions about rattlesnake behavior is that they are driven purely by warm temperatures. While it is true that rattlesnakes, like all reptiles, are cold-blooded and depend on external forces to get warm, temperature is just one of many factors that determine whether or not they’ll become active.

Here’s a great example that happened recently. In 2020, the Phoenix area broke several records for the hottest, driest summer in recent history. When rain finally came to the valley after more than 100 days without a drop, it was on a cold December day.

With temperatures barely breaking 50˚F, why would rattlesnakes suddenly become active? Simply: they have to, or risk death. With minimal effort, I was able to find 7 Western Diamondback Rattlesnakes on the surface hoping for rain. The first was found at just 45˚F, and the last at 51˚F. Comparing field notes for the day with a couple of knowledgeable friends, who also knew to put on boots instead of sweatpants for the day, showed similar results. Rattlesnakes, even in relatively cold temperatures, were very active. When rain fell again for a brief period on Christmas day, again, it was not difficult to find a lone Western Diamondback Rattlesnake coming out for a drink.

Just because we see rattlesnakes in the winter doesn’t mean you will.

People are often surprised that we are still able to find rattlesnakes in the winter – in fact it’s probably why you’re reading this right now. If you’re not someone that wants to run into them out there, don’t worry: it’s very unlikely that you will.

Rattlesnakes that we find in the winter aren’t in the same situation that you’d find them during other, warmer periods. They’re not out moving large distances, tracking prey, looking for mates, or any of the other behaviors that most often result in an encounter. This activity is much more specific – just coming to the surface of their den, and back down again when they’ve gotten what they need. That means that if you’re hiking on a trail and not purposefully searching situations that seem likely to house rattlesnakes over the winter, you’re not likely to see them at all.

More notes about rattlesnakes in the winter:

“I thought the rattlesnakes were hibernating!”

It’s December, it’s cold (for Arizona), and the Rattlesnake Solutions relocation team is still busy. Instead of picking up rattlesnakes from patios and porches, we’re pulling Western Diamondbacks from garages and sheds. Whenever this happens, a common comment pops up – “why are there still rattlesnakes out there? It’s Winter, I thought they were hibernating?” What is going on?

The answer is easy enough – why aren’t rattlesnakes hibernating? (or brumating, as is more accurate, with a note on that later) They are, and the places we catch them are where they’re doing it. As we have covered in previous articles about just how and why rattlesnakes choose garages as prime den real estate, rattlesnakes in the warmer parts of Arizona tend to have quite a few options for a survivable winter refuge. When a rattlesnake is found in a garage on a cold December day, it’s likely been there since October, and where it is found is where it was brumating. This is not the same as being active, being “awake”, or any situation where an imagined extension of rattlesnake activity has been extended because of a few warm days or any other reason.

“If it’s cold why are rattlesnakes still out?”

They’re not, they’re in, and that’s where you found them.

These cold-weather sleepy rattlesnakes are often discoveries by people using the holiday downtime to get to long-neglected projects, like cleaning out the garage or tearing down the old shed in the yard. Another common one throughout December are rattlesnakes found under boxes of Christmas trees and other holiday decorations that have remained untouched in the deepest corner of the garage for 11 months. These discoveries are small rattlesnake dens, of only one or a handful of individuals,

Here is a trio of Western Diamondback Rattlesnakes that I captured in a storage closet at an apartment complex in Cave Creek:

“But I saw a rattlesnake outside! Why isn’t it hibernating?”

As mentioned earlier, rattlesnakes don’t truly hibernate. Rather, they do something similar called brumation. This means they’re sleeping a lot and avoiding the cold, but if conditions are good for them, they may come sit at the entrance of their den and hang out or move around a bit. What conditions cause this to happen vary by species and location. Here in the Sonoran Desert, temperates can get chilly but not often dangerously cold, and moisture loss is a concern. They don’t necessarily choose sites that have a lot of sun exposure, or even avoid it altogether (Hamilton et al 2008). On some warm days, especially just before or after rain, or a bit of sun after a some winter sprinkles, rattlesnakes will often come to the surface to take advantage of it. That means that if you see a rattlesnake coiled in the backyard, it’s likely been in the area for quite awhile already, and is just coming out a short distance.

“I heard on the local news that rattlesnakes are coming out early, or are active longer this year because of the weather!”

There is no evidence to suggest this is happening, but somehow it’s still a news story each year. According to our call logs over the past decade, our observations, and other research, rattlesnakes are going into brumation (ingress) and coming out of it (egress) in about the same times as normal. That is, generally, in by the first of November, and out by the 15th of March. That means that the shoulder times around those dates are full of rattlesnakes moving around and traveling, so sightings may increase, even as general activity is considerably less than other times of year. This is when you should be keeping garages and gates closed.

How can I be rattlesnake-safe this Winter?

Refer to some earlier articles we’ve provided about rattlesnakes during the cooler months:

Is your home a rattlesnake den? How to stay rattlesnake-free this winter.

Holiday Rattlesnake Awareness Guide for Visiting Family

Spring is Here … Bring on the Rattlesnakes