Wildlife buttons up for winter
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Chel Anderson is a botanist and plant ecologist for the Minnesota Department of Natural Resources. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel.
Anderson: Hi!
Well, OK, as much as I hesitate to bring it up, winter is bearing down on us. Some of us are buttoning up our homes and preparing for cold and snow, but what about shelter if you live in the wild?
Anderson: Great question. Let’s talk about that. There’s so many things that we could talk about on this topic that I think we’ll try to limit it. First, let’s make the distinction between critters, like us, who are endotherms, who regulate our heat from the inside out and ectotherms, all these other living things whose temperature is regulated by the outside temperature. They don’t have any control over their own body temperature, so they’re really at the mercy of the outdoors. In that group, we have, first of all, snakes, garter snakes, and we have red-bellied snakes for the most part here. This time of year, in much of the county, you won’t see a garter snake or a red-bellied snake anymore, because they’ve already headed to the places that they’re going to spend the winter. Usually after the first couple hard frosts, they start making their way towards wherever they’re going to spend the winter in something called a hibernacula. And, more often than not, because in this part of the world we don’t have a lot of options of places to get below the frost line, these critters are going to spend the winter together. And so sometimes they’re in places that are traditional over many, many generations of snakes that snakes are moving to to spend the winter at. We don’t know about very many of these here in northeastern Minnesota, but there are some great locations that are known, say, in Manitoba, so even further north than here, where literally tens of thousands of snakes spend the winter together in what are, up there, sinkholes. So, at this time of year, the snakes here are moving sometimes along very traditional routes even to go to these places where they know they can safely spend the winter. They’re heading down into, it might be, under rock piles, talus slopes, fissures in cliffs, places that we can’t tell go down deep, but do go down deep into the ground, deep enough so that they get below the frost line. Once they get down there, they’re just going to get colder and colder and colder, but they’re not going to freeze. They can’t tolerate freezing, snakes can’t, so they have to find someplace that’s going to be reliably above freezing for the winter. They’re going to stay alert, but sluggish, so if their hibernacula would allow them to go deeper, should it get colder than it normally does or maybe there’s less snow cover and that’s affecting their particular spot, then they can move lower if they need to. But, if things get bad and they can’t go any lower, and it gets too cold, then there’s obviously a lot of mortality. It’s not about giving off any heat; it’s about the fact that there are limited numbers of places where this is possible.
No, I wouldn’t think so.
Anderson: So, think about it, if we only had a few shelters for humans through the winter here, we’d all be there, and we’d pile in pretty deep, I bet.
That sounds like a bad horror movie to me, Chel.
Anderson: Well, I know especially for people who are a little bit leery or phobic about snakes anyway, it’s not a happy thought. But, it is an amazing thing to see. I’ve only had the good fortune of stumbling upon one of these hibernacula one time, but it’s just incredible to peek down into some depth and see all these snakes together. So, that’s what snakes are doing. An amphibian that’s common to our area here, salamanders, so that would be the red-backed salamander and the blue-spotted salamander, they are also not tolerant of freezing. So, they have to find places to go and very little is known about where our salamanders are going in the winter, very secretive all throughout the year and we don’t really know a lot about it, but it’s suspected that they’re using the tunnels of the other critters that are doing the same thing. So, it might be chipmunk tunnels or woodchuck tunnels; who knows what all kinds of entrances. We might be able to go down some little space around roots of a tree that go deep from the surface. And, of course, they’re also going to be very dependent on having good snow cover, because snow cover makes a huge difference in how deep that frost goes in the ground, as most of us know. Let’s talk about insects, so butterflies. This is the time of year when people may have been seeing on the warmer days that we’ve had a lot of the small butterflies of a variety of different kinds; morning cloaks, commas, tortoiseshells, there are a number of species in those latter two groups. And, they’re going around looking for a sheltered, unheated space to spend the winter to kind of get tucked in. So, before we were inhabiting the landscape, they would have used under the big flakes of tree bark or in the fissures of tree trunks or under some kind of bark, you know, that was maybe propped up against something. So, they’re looking to mostly hide themselves. They can tolerate freezing, they’re adult butterflies, and they’re going to go through the winter frozen, basically. But, they need to hide from things that might want to eat them. So, there are going to be birds and mammals out there looking for things to consume over the winter, and they want to be out of sight, out of mind, out of harm’s way, that way. On the mammal side, in a similar way, we have snowshoe hares that are changing color rapidly to their winter white. They, of course, are an endotherm, like we are, they’re regulating their own body heat, but they are using, similar to the butterflies, a camouflage strategy: “OK, I’m going to change my color here, because that keeps me safer.” So, that’s a form of shelter, a different kind of shelter than we maybe normally think about, but it’s a form of shelter, and it can backfire in some years where you change color before the snow shows up, so I’m sure they’re hoping that the snow comes sooner rather than later.
Chel Anderson, DNR botanist and plant ecologist. Thanks for helping us understand what’s going on around us this fall.
Anderson: My pleasure.
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