Snakes, being cold-blooded, rely on their surroundings to regulate body temperature. Like other ectothermic animals, they bask in the sun to warm up, seek shade or water to cool down. So, when conditions are not conducive for temperature regulation, they brumate.
While hibernators and brumators both experience lower body temperatures, metabolic rate and breathing, brumators do not sleep the season away or rely on energy reserves. Brumators actually are alert—albeit sluggish—and may move around and drink. Snakes must brumate below the frost line to avoid freezing. If not, ice crystals could form in their body, resulting in death, according to Jeff LeClere, an amphibian and reptile specialist with the Minnesota DNR and author of the online “Field Guide to Amphibians and Reptiles of Iowa.”
Since snakes can’t burrow, they search out existing hibernaculums. For some, like milk snakes and rattlesnakes, that means deep crevices in rocky outcroppings. For others, like garter and bull snakes, that means animal burrows, abandoned wells and caves. These locales can harbor a single snake, or thousands.
Cold-blooded not withstanding, snakes have no choice but to brumate. Winter removes their favorite food sources—mice, earthworms, fish, frogs and insects. Even if food were available, digestion is impossible because metabolism is virtually halted. Thus, food in the stomach would rot—with fatal consequences. Snakes will often quit eating a couple weeks to a month prior to brumation.
Never fear, though. Once temperatures rise in the spring, these beneficial pest-eating reptiles will return. Just make sure to give them a “brake” when you’re mowing.
This article originally appeared in the January/February 2010 issue of Iowa Outdoors magazine.
Learn more about Iowa's snakes and other critters on our Iowa Wildlife and Iowa Outdoors Magazine boards on Pinterest.