Friday, December 03, 2010

Lessons from nature

Are you stressed? It is that time of year when stress has a way of creeping into our lives. Not only are the holidays upon us, but it's winter in the northern hemisphere.  So on top of the regular things like work, money, school, kids, parents and holiday shopping, we are also faced with driving in terrible weather, staying warm, shoveling our walks and driveways, keeping from slipping on the ice. And how do we deal with all this stress? If you're like me, you'd enjoy nothing more than curling up under the covers and sleeping until spring. But no, unfortunately we can't really do that.

So instead what do we do? Well some of us don't do much, so we get sick. Maybe we exercise, scream, take a break, relax, eat, cry. Or, or...we don't deal with it much and just leave. Head south.

Animals and plants are also dealing with this stressful winter time. But for them, the only thing they are trying to do is survive. Just plain old get through until spring. So what specifically stresses them out? Well, winter provides plenty to worry about for them: a definite shortage of food, low quality of the food that is still around and accessible, sever cold temperatures, much less cover with all the leaves off the trees and shrubs, deep snow which also happens to be white, and of course most of the water is frozen.

Frozen pond. 
Those ducks back there have found a tiny bit of open water, but some are sitting on the ice.

 It really is quite pretty. I'll give it that. Beautiful actually.

Look at those incredible ice crystals.

But obviously, nature has found a way to deal with all of that. They do so in three main ways:
1) Avoiding winter -either by dying or migrating
2) Take an inactive response to winter through some level of dormancy (what most of us would like to do)
3) Actively respond to winter through a variety of adaptations and strategies.

So, let's look at each of these for a bit.

Avoiding winter
Dying: Some plants and insects actually avoid winter just by kicking the bucket. That is, they produce seeds or eggs that can overwinter, while the adult just dies.

Migration: Some animals up and leave. But not all of them are capable of leaving, or I assume they all would. Smaller animals generally can't move far enough or fast enough. Larger animals often migrate from higher elevations to lower elevations (which is why we have a wonderful heard of elk in the valley right now).

Inactive Response to Winter
Hibernation: The most commonly known form of dormancy. Pretty amazing really. The hibernating animal's metabolic rate slows way, way down which in turn lowers body temperature, slows breathing, burns less energy (fat reserves) thus keeping hold of those limited energy reserves longer. That really is what winter survival is all about - maintaining those energy reserves. That is generally done through eating and building fat.

Torper: A bit less known. Torper is very much like hibernation, only for temporary periods of inactivity. Several hours to a day or two. Some birds, like chickadees, do quite of bit of torporing (I don't think that's a real word) through the winter.

Active Response to Winter
These are the animals truly out there surviving it. There are several ways nature actively responds to the many stresses of winter. For those animals that stay, the major source of warmth is internal heat (internal ovens), generated by digesting food or metabolizing fats. So here are different ways animals have adapted to moving through deep snow, dealing with the whiteness of it all, low food sources, etc.

Flexible legs/deep snow mobility: The moose (and other large mammals) has very flexible legs and can lift each front leg out of the snow and move it nearly horizontally above the level of the snow before setting it down for another step. This flexibility allows the moose to move in chest-deep snow.

Over-snow movement (low foot load): Larger feet compared to the size/weight of the animal disperse the animal's weight over a larger area of snow, allowing the animal to move effortlessly over the snow. We as humans saw  how effective this was, and devised our own larger feet for over-snow movement.

Snowshoe hare tracks on snow.

Our means of over-snow movement. 
Those are snowshoes buried in the snow, if you couldn't tell.

Snow-free or lower snow pack: In these locations, the impact of the weather or snow pack is reduced. Animals successfully seek out locations with shallow snow packs or places where snow crusts have not formed. Deer can often be found on warmer, south facing slopes with shallower snow pack. 

Herding: As demonstrated in a couple of the photos above, larger bull elk will form separate herds from the cows and calves. Herding provides a couple of benefits. First, more animals means more eyes to watch for predators. Second, more animals means more feet to pound the snow from the ground for grazing.

Subnivean excavation: I love that word, "subnivean", which basically just means under the snow. Life in the subnivean environment is generally more sheltered  from some of the stresses of winter. The ground-snow level is warm relative to the air during the winter, and conditions are a bit milder. The impact of wind and cold are reduced, but moisture, carbon dioxide, oxygen and light become more important issues. These additional limitations may impose their own stresses that could reduce the number of individuals that survive the winter.

Color change: Some animals (predators and prey) will get a new winter-white coat to match the surrounding landscape. The weasel (ermine), for example, will slowly "molt" away its luscious brown fur which grows back  snowy white. Snowshoe hare also turn white in winter, but their fur simply lose the color pigment, rather than losing and re-growing new fur.

Coprophagy: In other words, "double-digestion". When food quality is so poor, it's hard to get enough water and nutrients out of it, and much is lost simply through the ever-present act of a bowl movement. Water and nutrients often just pass right through an animal leaving it much wanting. Some animals, like ungulates, have multi-chambered stomachs to help absorb all it can from woody food. But little critters, like cottontail rabbits don't have that strategy. So they must engage in coprophagia. They must, in the name of survival, re-digest their scat in order to further absorb what might otherwise have been lost. Nose clip, anyone?

And there are oh, so many other ways wildlife survive the winter. It's exciting to me when I come across something like this:

Little animal tracks in the snow. This tells me those incredible adaptations are working. Survival is the job - adaptations are the tool. These animals are dealing with those winter stresses and surviving it.


Felicia said...

Gorgeous shots! I do enjoy winter (maybe because I live in Florida, where we don't have to deal with blizzards). But it still gets cold enough to put frost on the ground, and this morning, I saw the prettiest ice-crystal pattern on my windshield. It was a nice little morning treat!

Jenny said...

I may share your post with my kids teachers. You explain things well.