BIOLOGY OF TRANSITIONS

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BY HANNES THUM

How animals and plants react to winter in our region is more confusing than we may realize.

The term “hibernation” is used in a variety of contexts and often is misused or oversimplified because the whole suite of mechanisms that creatures use to, generally speaking, shut down or slow down their bodies in winter and then ramp back up into full metabolism in the spring is incredibly diverse (Bernd Heinrich’s book, “Winter World,” is an amazing resource on the trouble with using a single term to describe all these different biological processes).

Some animals, for instance, lower their body temperatures dramatically in winter (the Arctic ground squirrel is an amazing example of this), but some do not. Some plants show almost no signs of life in winter, but some do. And what is the most fascinating (I think) part of the biology of these seasonal transitions is there is still so much we don’t know about how creatures time their winter adaptations.

Our valley is full of creatures “waking up” from winter, including the aspen trees with new buds and the mammals becoming more active after a winter of patient waiting (and, sometimes but not always, hibernating), but scientists still can’t explain all of this simultaneous renewal of life each year.

My favorite part about science has been the realization that biology has figured out only some – and probably just a tiny fraction, at that – of what knowledge this planet has to offer us. Biologists have sorted out a few of the ways the organisms determine when to put their bodies into modes of winter adaptation and when to “awaken” to take advantage of spring. Some plants, for instance, have been shown to use certain light-sensitive chemicals in their bodies that help them keep track of different amounts of daylight and nighttime hours to trigger seasonal hormonal changes. And some of our local animals have been found to react to temperature changes that either slow down (in the autumn) or speed up (in the spring) their metabolisms to either decrease or increase their caloric demands.

But what scientists know about how creatures match their own internal chemistry to the annual seasons absolutely pales in comparison to what we don’t know. There are many mysteries still to solve about how exactly plants and animals in regions like ours “know” when spring has arrived. These unanswered questions, I often find, are more interesting than the answered ones, and I hope that budding biologists find inspiration in these unknowns.

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