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Is putting a spider outside during winter actually humane? Science has the answer

Look at that sweet little face! What's a softhearted but squeamish Minnesotan to do?

Look at that sweet little face! What's a softhearted but squeamish Minnesotan to do? Getty Images/iStockphoto

It’s high December. The snow is fluffy. The nights are long and perpetually near.

During these hunker-down days, when you’re safe and warm in your house or apartment, there will come a moment when you turn your head and lock eyes with the roommate you didn’t know you had: a brown, fuzzy-legged, thick-bodied spider.

Someone will immediately suggest killing it. Someone always does. But there’s usually also that dissenting voice in the room, the one that mercifully intervenes.

No, they’ll say. Don’t kill it. Put it outside.

But in mere hours, temperatures are going to be in the low teens, and the snow is already halfway up your calf, and you may wonder to yourself: Is putting the spider outside really the humane thing to do?

You don’t have to wonder anymore. Science has the answer. That said, you may not like it.

Spiders are just like eight-legged little people in that they are accustomed to living in certain spaces, at certain temperatures. Spiders from down south prefer a hotter climate, and spiders from up north generally know how to weather the cold.

Cold-hardy spiders have bodies that can produce a kind of antifreeze compound that keeps them from becoming popsicles while they hunker down under leaf litter or tree bark for the season. They even raise their spiderlings in insulated egg sacks until it’s warm enough for them to come outside.

But according to Rod Crawford, the curator of arachnids at Burke Museum of Natural History and Culture, you’re probably not living with a Minnesota spider.

“The American house spider is probably native to northern South America,” he told Live Science.

So how did a tiny, eight-legged Brazilian end up in your Minneapolis apartment? Same way you probably did. Its spider ancestors migrated there from other parts of the world -- though, unlike your ancestors, it probably hitched a ride in a shoe or a suitcase.

At this point, it is no longer a Brazilian backyard spider or a Minnesota spider -- it is a house spider. Its home is in your house, and if you put it outside when the weather is cold, it will very probably die. Even spiders that come to our neck of the woods from temperate places like England (the giant house spider, for instance) tend to struggle outdoors.

Not even cold-hardy spiders native to Minnesota are safe. Building up that miraculous antifreeze takes time. University of Wisconsin-Green Bay biology professor Mike Draney told NPR that putting a spider outside in the middle of December when it hasn’t prepared for winter is, essentially, “a death sentence.”

So if you really care about the spider’s life -- if you really, really don’t want to hurt it -- then putting it outside is probably the last thing you want to do. If you can’t stand being in the same room as a spider, try putting her in your nearest basement, or a garage, if you can. That should be plenty warm for her to survive without you nearly stepping on her every other day.

Or try Draney’s suggestion: Just leave her alone. An adult spider has probably eaten at least 40 insects, and will continue to eat more if you let her. And spiders, as a rule, prefer to spend most of their time wherever you aren’t. Next time you make unexpected eye contact with your unexpected roommate, try looking away.

When you turn around, she’ll probably be gone.