Eastern Diamondback Rattlesnakes often brumate in the burrows of the Gopher Tortoise, rotted out stump holes, or root systems under saw palmetto. The snakes can often be found sunning on warm winter days near the entrance to these burrows. The snakes do not enter a true "hibernation" like bats* do.
During very hot periods, the snakes will enter a period of inactivity known as aestivation
* I originally had bears here as an example of true hibernators. I received the following from Kelley Weitzel, Sr. Preserve Naturalist, Pelotes Island Nature Preserve:
"I enjoyed exploring your site a bit. One point – on the brumation page, it says that reptiles do not truly hibernate like bears do. FYI – Black Bears don’t really hibernate. It’s more of a slowing down like brumation. (Bear hibernation is an old wives’ tale that we’ve all grown up with.) If you need an animal to compare it to instead of bears, many kinds of bats DO hibernate. If a bat is awakened mid-winter, it will probably not survive because waking up will use the physical reserves it needed to make it through its true hibernation. (Bears often do wake up and even give birth during their pseudo-hibernation.) Thanks for providing such a wide range of venomous snake resources for the public!"
Thanks much for the cool info!