Friday, March 20, 2009

Something's Changing

A few days ago, vole tracks appeared.

Since arriving, I'd seen maximum two trails left by subnivean creatures. In the last few days, they are suddenly everywere: around the office, around my cabin, doodling around the commons in loopy trails from under one building to another or in fairly straight lines across the road.

Subnivean creatures, by the way, are the tiny rodents: mice, shrews, and voles. Subnivean (for those of you who weren't in any of my field trip classes this year) means "under snow." Under the deep snow is an insulated layer where these animals build tunnels through the dead grasses to stay warm, find food, and hide from predators.

Shrews have long pointy snouts and can be aggressive insectevores. I'm hoping to find evidence of the water shrew this summer in our wetlands and lakes. Water shrews are badass.

Mice and voles are basically indistinguishable. I've heard contradictory evidence as to whether mice are actually native to Alaska or have been introduced, but there are a vareity of vole species native to, and even unique to, different regions of the state. They look cute and cuddly and they can be serious pests to home owners.

Usually these animals stay in the subnivean all winter except maybe to reach grass heads above the surface or if they are forced out of their tunnels by packed trails. In our field trips we talk a lot about how trails negatively impact subnivean residents with an aim to promote lower impact recreation (for example, using established trails for snowmachining or using a frozen lake area).

Trails can also impact plant life, partly because packed snow takes longer to melt -a big concern in an area with such a short growing season- and also because packed snow reduces light cues that reach the soil.

Plants rely on light cues, rather than temperature, to initiate their growing cycles. Thus, even with a cold spring or warm fall, deciduous trees will still grow new leaves or display fall foliage and eventually go dormant. There are still temperature considerations, of course; nothing can happen while all the water in the ground is still frozen.

Trails aside, what has sparked the sudden infusion of tracks? What has happened to make all these voles suddenly appear out from their safe, warm, food-filled subnivean tunnels?

The temperature hasn't changed. The range has been the same since I arrived: nights down as low as -20, days up to 30 or 35. The snow hasn't gone away. There is no new food source that I can think of.

Today I actually saw some voles. I glanced out at the bird feeders we keep on our windows. The chickadees, red poles, and nut hatches use a few nearby spruce trees as their access point to come to the feeder, grab a sunflower seed, and return in order to eat it. Under the trees where not as much snow has built up there is a patch of dead grasses. The voles were darting in and out of view through the grasses, eating bits of dropped sunflower seeds, I suppose.

The presence of dropped sunflower seed hasn't increased. It's possible the voles have been doing it all winter, but I've spent a lot of time looking out that window and today was the first time I've seen it. That, combined with the sudden profusion of tracks, makes me thing something has happened to encourage these creatures to emerge from their subnivean world.

I look to the light. Today is the first day of spring. This week we had our twelve-hour day. Like the plants, I imagine these creatures take their cues more from light than temperature as they prepare for the growing season that will come.

Predators still abound, so whatever could encourage them to seek out food sources that expose them to eagle eyes (literally) must be pretty darn important. More important than keeping themselves alive, which they've already been doing just fine all winter long. My guess: babies.

Mating season is upon us, folks.

There's a reason Bambi's friend Owl talks about twitterpating. In other places it corresponds to the melting snow and emergence of new plant growth. In Alaska, waiting that long to get it on wouldn't leave enough time to adequately reproduce in number before temperatures dropped again. So the mice, shrews, and voles sense the stronger, longer rays of sun filtering through the snow to their tunnels and say to themselves, "hooray! spring is coming! time to make babies!"

At this point, I don't know if those babies already exist (if so, Round 1 of several for the year, I'm sure) or if the voley-poos are merely preparing themselves physically to be able to reproduce, but either, way, I like seeing their tracks everywhere. They're pretty cute.

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