This page talks about hibernation: whether you need to hibernate your snakes, and how to do it.
Hibernation in reptiles is called brumation: it’s different from hibernation in mammals in that the reptile is not living off its fat reserves. Instead, its metabolism, which is of course temperature dependent, has slowed down so much because of the cold that it hardly uses any energy over the course of the winter. It’s still awake and still active (though very sluggish), but it’s cold enough, and its metabolism is slow enough, that it actually doesn’t lose any significant weight during the winter.
Should your garter snake be brumated? The short answer is: it depends. It’s not a requirement — many snakes stay warm, active and hungry throughout the winter with no adverse effects — but there are a couple of situations where brumation may be necessary.
If you want to breed your snakes, brumation helps their fertility; bringing them out in the springtime helps reset their internal clocks and lets them know it’s time to mate.
Sometimes, though, the snake doesn’t give you any choice. Some time during the fall it decides to refuse food that it would have attacked with enthusiasm only a few weeks before. The change in light levels, length of day or temperature has signalled to your snake that fall is here and that it should stop eating in preparation for brumation. In some cases the snake starts eating again after a month or so or after offering it something it’d rather have (sometimes they get finicky in the fall; see Problem Feeders), but in other cases you have to brumate them.
Why do they stop eating? Snakes are cold-blooded and need to be warm in order to digest their food. If they’re too cold, they can’t digest their food. Anything remaining in a cold snake’s stomach will putrefy before the snake can digest it. That’s deadly. So they clear out their systems before they go underground.
Whether it’s the snake’s idea or yours, brumation is not difficult. Here’s how I’ve been doing it with my snakes.
First, stop feeding the snake if it hasn’t already done so itself. After about three weeks the food is usually cleared out of its system. After that, give the snake a bath in lukewarm water to encourage it to defecate the last remaining bits out of its system.
Then it’s a matter of finding a place with a cold enough temperature. I once lived in a drafty apartment that was really cold enough in winter to hibernate most North American colubrids: around 12-15°C (55-60°F). That’s probably the high end of an acceptable hibernation temperature; many snakes, especially the more northerly species, could go colder than that.
How much colder? Their temperature cannot get below freezing without hurting or killing them, so you probably don’t want to go below 4-5°C (40°F) under any circumstances. But anything in the fifties Fahrenheit (10-15°C), or even the high forties, is probably ideal. How you get those cold-enough temperatures is the trick. Some people use old fridges, cranked as warm as they will go, others use basements or fruit cellars. Use a thermometer.
Remember: if it’s too warm, the snake’s metabolism will still be too high, and it will lose weight. If you can’t get the snake cold enough, you may want to give up on hibernating it.
Bring the snake’s temperature down gradually. Keep it in hibernation for up to three or four months or so. Check on it periodically. Make sure it has access to water. It can be in its own cage or in a smaller container — it won’t move around much at those temperatures!
When it’s time, bring the snake into warmer temperatures gradually — back to room temperature, back on heat, and then, a few days later, offer it food.
The idea, if nothing else, is to make sure that the snake’s internal clock is reset so that when it’s brought out again, it thinks it’s spring and it’s time to eat again. And possibly time to mate.